Battery Not Charging after Polarity Change

[Space54]

On our way to Daventry in the new Jupe, 20 miles out , ignition warning light came on-fan belt was still where it should be so decided to turn round and come down in a "modern" as still 100 miles or so to go! Was probably the right decision as 5 miles or so from home had total power failure bringing everything to a grinding halt! Initial fault would appear to be something as "trivial" (?) as a loose wire to the ammeter as when this was tightened most everything was restored and the car would start again (some incompetent had left a wire loose when doing the ground polarity change!). The only (but rather significant) issue outstanding is that the ignition warning light is still staying on and the newly wired ammeter would seem to confirm that the dynamo is not charging.

Did the dynamo output check last night (joining the D and F dynamo terninals and measuring volts with engine running between the joined terminals and earth) and got only 1-3 volts whatever the engine speed. Field winding fault almost certain??

I also recall noticing that just before the ignition warning light initially came on and having been driving for at least 40 minutes the ammeter was to the right almost full scale indicating a 20 amp+ charge? Would this be indicative of cut out failure in the control box? Not sure which is the chicken and which is the egg here, but if the dynamo was charging at "full whack" for a sustained period could that result in a "burn out"?

Anyway folks I guess my main question to experienced Jowetters is what are my options assuming I am suffering from dysfunctional dynamo and/or voltage control box? Is Jowett Spares my best option or am I in need of other specialist(s) for new/ service exchange/ repairs?? Advice much welcome and appreciated, bearing in mind that having been deprived of my first major outing in the car I'm keen to get her up and running again soonest!

By the way was a little surprised that neither fuse blew during the aforementioned proceedings-although one seems to have got quite warm as the small piece of paper bearing the 50 Amp rating shows signs of scorch?!
Thanks
Keith

[Forumadmin]

Have you done all the quick test and all the full test?

If you have blown the field coil we need to find out why and issue a health warning. It may be that when doing the polarity change too much current for too long went down the field coil.

I suspect it may be the regulator. It takes some doing but setting them up is worth it. Clean all the contacts first.

Do this before going to the expense of getting new components.

I thought the fuses should be 30A!!
Did you swap the Ammeter leads around?

[Amy]

Keith, I'd check your regulator. We had (quite a few) problems with the one on my SC, and it may well be worth checking that it's set up properly and that nothing needs cleaning / tweaking. If the ignition light is staying on, it means that no charge is being put through to the battery, and we saw this symptom on my car as well.

If the regulator is not working properly / not set up properly that could also account for the ammeter showing odd readings, as the regulator won't be doing its job of regulating the currents going through the system.

Dad (forumadmin) has linked the tests that you need to do, run these and see what the outcome is. If you need any help with them, do just pop a post up here and we'll do our best to help

Good luck,
Amy.

[Space54]

Have you done all the quick test and all the full test?

If you have blown the field coil we need to find out why and issue a health warning. It may be that when doing the polarity change too much current for too long went down the field coil.

I suspect it may be the regulator. It takes some doing but setting them up is worth it. Clean all the contacts first.

Do this before going to the expense of getting new components.

I thought the fuses should be 30A!!
Did you swap the Ammeter leads around?

Hi Keith, Amy and all others!

I did swap the ammeter wires over when I changed the ground polarity as it was seemingly not tightening one side of the swapped wires that instigated my problem. It was only the "quick" dynamo test that was performed, but as this showed only about a volt output surely this confirms a dynamo fault irrespective of any other faults on the regulator. (Putting it another way am I right in assuming that a fully functional regulator cannot suddenly restore the lost ouput of the Dynamo?)

I am desperate to join Pauline and keith Winteringham in their Jupiter on SUNDAY and therefore seek a very rapid solution! I am minded to consider an alternator conversion(I was anyway in the medium term) and note that Pheonix Marine Electrics in Daventry are offering brand new Lucas ACR 17 at £53 delivered! Keith's guide speaks of the need "to fabricate a new bracket"- I assume the nature/dimensions of this are now well established and can be done fairly readilly? This would seem a very nice solution as the regulator would no longer be required or am I missing something?!!
Best wishes
Keith

[Forumadmin]

The bracket is to support rear of the alternator since it is shorter than the dynamo. You can put a long set bolt (say 2.5 inches) and through some pipe (or loads of washers) to space it out.

When you tested the dynamo did you rev it up to about 1000 rpm? I did this on the bench with a power drill.
Have you also checked the continuity of the field coil? One of my dynamos simply required a repair to reconnect a broken connection. Check this from the F terminal wire at the control box end (diconnected from CB)!

Recommendation is to fit an alternator; but make sure you never run it disconnected from the battery else it blows the diodes..

[Space54]

The bracket is to support rear of the alternator since it is shorter than the dynamo. You can put a long set bolt (say 2.5 inches) and through some pipe (or loads of washers) to space it out.

When you tested the dynamo did you rev it up to about 1000 rpm? I did this on the bench with a power drill.
Have you also checked the continuity of the field coil? One of my dynamos simply required a repair to reconnect a broken connection. Check this from the F terminal wire at the control box end (diconnected from CB)!

Recommendation is to fit an alternator; but make sure you never run it disconnected from the battery else it blows the diodes..

Thanks keith,

is there any issue with the tacho drive-can this be driven off the alternator?
Cheers
keith

[Forumadmin]

The tacho drive would need some heavy modification to attach to the alternator. Suggest you put electronic inards into the original facia.

You may have to fit the pulley from a dyno onto the alternator as the fan belt will not fit the normal alternator pulley. You might find a toothed belt section to fit all three pulleys.

[Space54]

Turning into a bit of a saga folks, but I guess some progress being made! Having failed the quick in situ output test with a showing of only 1-2V took the dynamo off and took it for "refurbishment" only to be told that there was absolutely nothing wrong and the unit was a "masterpiece of British engineering!"

Refitted the dynamo-making sure both connections good and tight and lo and behold ign warning light now going out and ammeter showing plenty of charge!

HOWEVER-for plenty of charge read too much charge as at 1500 RPM ammeter showing full scale deflection charge and battery reading just over 16Volts-no signs of charge dropping out. OK so now must be a voltage regulator problem? Have read the Lucas booklet and although I feel I'm getting the drift if someone could summarise what adjustment is required to stop the dynamo charging to excess I would be very grateful!

Making VR adjustments with the engine running sounds like a bonnet off Job? Might it be expedient to fit a new unit and examine the existing one at leisure?!

That being the case is this linked one, the one I need?

http://www.classicpartsworld.co.uk/luca ... ator-rb106

Thanks again for all help and advice!

Keith

[Forumadmin]

It is probably not an adjustment but a loose connection or sticking contact. TOPIC You could just try to understand what causes the fault. It will be the voltage regulator. Suggest you follow this explanation in the Gallery and then do the full fault finding guide.

Since the car has been off the road for a while a simple recon by taking the regulator off the car and cleaning will do the trick. There might be a broken wire; but I doubt it. The circuit is not that difficult

[Amy]

Turning into a bit of a saga folks,

Ah, welcome to the wonderful world of Jowetteering! You're far from alone, we've all been in the situation of having an apparently simple issue for it to turn into something far less simple. It's all worth it on a sunny day when you're motoring down a country lane though

took the dynamo off and took it for "refurbishment" only to be told that there was absolutely nothing wrong and the unit was a "masterpiece of British engineering!"

Great news - that means you (probably) only have one issue to sort out. And a decent dynamo

HOWEVER-for plenty of charge read too much charge as at 1500 RPM ammeter showing full scale deflection charge and battery reading just over 16Volts-no signs of charge dropping out. OK so now must be a voltage regulator problem? Have read the Lucas booklet and although I feel I'm getting the drift if someone could summarise what adjustment is required to stop the dynamo charging to excess I would be very grateful!

Regulator problem.

I think dad's linked the diagram you need - sounds like the contacts aren't closing at the right point and thus allowing the charge to continue when it shouldn't (they cut off the circuit when they close IIRC). It will just need a bit of TLC with cleaning and checking that they are at the right gap, etc. Shouldn't take too long (sorry, sorry, fatal thing to say!) and is quite a simple job as they're not complicated bits of kit.

If you're stuck once you've got it off and the innards exposed, do feel free to ring for advice - dad's probably a better bet than me as he's rather more experienced in all things Jowett, number in membership list (sorry dad...!) We had these issues with my SC last year though and went through all the steps so it's all quite fresh in the memory.

Best of luck,
Amy.

[Forumadmin]

And how pleased with yourself you will be when you fix it yourself! So you can help a person with the same problem.....

[Amy]

Making VR adjustments with the engine running sounds like a bonnet off Job? Might it be expedient to fit a new unit and examine the existing one at leisure?!

Sorry Keith, missed this bit with my previous reply.

No need to do any of the adjustments or fettling with the engine running, and definitely no need to take the bonnet off!!

Take the regulator off the car, and then there are a few stages that you can go through to check it out. They're all detailed in one of the manuals - I'll check tomorrow which it is, it's one of the Jowett manuals I think - and it basically gives a step-by-step troubleshooter. If they're not already on the gallery we can scan them and put them up there for you.

Amy.

[Chris Spencer]

Keith - Good source of period electrical spares is www.holden.co.uk - but I think you will find the most helpful & knowledgeable on the parts / stock front will be our own guys at Jowett Spares.

[PJGD]

I have a number of Lucas Service Manuals that cover the various electrical sub-systems various. As time allows, I will scan them and post them in the Gallery.

I have just scanned an easy one on "Vehicle Wiring" which addresses the polarity change to some extent. Unfortunately, having scanned it at 300 pixels/inch, the file size has come out too large to upload to the Gallery, so I will need to re-scan it at ~150 pixels/inch. In the mean time, it is available for download here:

http://pdingle214687.home.comcast.net/T ... t_1964.pdf

Philip

[Forumadmin]

This is the pdf at about 2MB

Lucas_Vehicle-Wiring_Training-Booklet_1964-com.pdf

I have OCRed the text which is below and the pictures in B/W so the files are a lot smaller. Click on the pictures to get a good view.

Figure 1. A SIMPLE ELECTRICAL CIRCUIT
Before we consider vehicle wiring, let us first describe the simplest type of
electrical circuit. It consists of a source of supply (usually, the battery), an electrical
unit (for instance, a lamp) and two conductors (or cables), known as the 'feed' and the
'return'.
The 'feed' supplies current from the battery to the unit. The 'return' completes
the circuit from the unit to the battery.
*****
Figure 2. AUTOMOBILE CIRCUIT
All car electrical circuits include a switch in addition to the unit and battery.
There are then three wires in the circuit: the feed, the switch wire and the return.
Normally the switch is positioned in the feed. However, there are occasions when the
switch is in the return.
* * * * *
Figure 3. INSULATED RETURN CIRCUIT
In practice, there are two methods of connecting car electrical circuits, depending
on the type of return to the battery. The insulated return system (sometimes referred to
as the double-pole system) uses insulated leads for both poles, or sides of the circuit.
The earth return system (or single-pole system) makes its return t.o the battery through
the vehicle frame or chassis.
Prior to 1932, the insulated return system was used almost exclusively. It is
now used on larger vehicles only, such as passenger service vehicles and petrol tankers.
The great advantage of the insulated return system is its protection against
short circuits to Earth. Hence, the risk of fire is very much reduced, but it involves
increased expenditure.
*****
Figure 4. EARTH RETURN CIRCUIT
The earth return system is now used on the majority of modern cars. (This
applies not only to the British Cars, but also American and Continental models).
As the return to the battery is through the frame or chassis of the vehicle, the
earth return circuit leads to a reduction in the amount of wiring. This results in more
economic production and a less complicated wiring layout.
*****

Lucas_Vehicle-Wiring_Training-Booklet_1964_Page_17_Image_0001.jpg

- 1 -
Figure 5. POSITIVE EARTH AND NEGATIVE EARTH
When the earth return system was first introduced, it was usual to connect the
negative terminal of the battery to earth. It was, therefore, known as the negative earth
system.
It was later considered that certain advantages were obtained by earthing the
positive pole of the battery instead of the negative. Thus, we had the introduction of
the positive earth system, which is used on practically all British cars and commercial
vehicles today except those specialised vehicles previously mentioned.
It was claimed that the positive earth system led to a reduction in the amount
of corrosion at the positive battery connections. This was the case when battery
connectors were made of dissimilar metals. At the present time, non-corrosive materials
are used, and the corrosion of battery connectors has ceased to be a problem. It is
now considered unlikely that the negative and positive earth systems have any great
effect on the amount of corrosion at the battery connectors.
However, regardless of the polarity of the electrical system, it is an advantage
to have a negative spark. We discussed this point in the Coil Ignition section. The
standard fluid-filled coil is wound to produce a negative spark on a positive earth
system, but, by reversing the primary connections, the same coil can be used to produce
a negative spark on a negative earth system. The turns ratio of the modern range of
coils has been increased, so that the H. T. output is more than sufficient, even when the
primary connections are reversed.
We should perhaps clarify the position regarding terminal markings.
1. Some coils have terminals marked '+' or '-' . One version is available for use
on both positive earth and negative earth systems. The terminals are connected
in accordance with the polarity of the system. (For instance, '+' is connected
to the contact breaker, on positive earth systems, and to the ignition switch, on
negative earth systems).
2. Many coils are still supplied with terminals marked 'sw' and 'CB'. A
standard positive earth coil, marked 'sw' and 'CB' can be used on a negative
earth system, and will provide a negative spark, providing the connections
are reversed externally. That is, 'CB' is connected to the ignition switch, and
'SW' to the contact breaker.
A special negative earth coil is, however, supplied to the vehicle manufacturers.
The windings for this coil are exactly as for the standard positive earth coil,
but the primary connections have been reversed internally. When this special
coil is used, therefore, 'CB' should be connected to the contact breaker and 'sw'
to the ignition switch.
* * * * *
- 2 -
Figure 6. TYPES OF CABLE
We are now in a position to consider the types of cable used for wiring cars.
There are three main groups.
1. Starting Motor Cables.
2. Ignition H.T.
3. General Wiring.
We should, perhaps remind you that the cross-sectional area of the cable conductors
is determined by the amount of current flowing in that particular circuit and
tl)e amount of voltage drop. (The voltage drop in any circuit must not exceed 10% of
the battery voltage.
*****
Figure 7. STARTING MOTOR CABLES
1. The most generally used pattern is a fairly light type of jute covered cable
as shown. This comprises 37 strands of No. 20 SWG tinned copper wire, (or
37/·036).
It is suitable for most light vehicle work where the starter motor current does not
exceed 300 amperes.
2. There are two heavier starter cables of similar construction to the light one,
i.e. jute covered, but they have 61 strands of No. 20 or 18 SWG., (61/·036,
61/'044) and are used for starter currents up to 500 amperes and 1,000 amperes,
respectively.
Where this size of cable is used for the starter supply further lengths may be
made up for the bonding strip and return to the battery.
*****
Figure 8. EARTHING LEAD
The earthing lead for the starting motor circuit consists of flexible braided copper
cables. Two sizes are used.
1. When the supply lead is made of 37;036 cable, the earthing lead is 16 x 16 x ·012.
That is to say, the cable consists of 16 bundles, each of 16 strands of wire,
the diameter of which is '012". (This wire is also described as No. 30 SWG).
- 3-
2. When the supply lead is of either 61/·036 or 61/'048 cable, the earthing lead
should be 32 x 16 x ·012. (That is to say, 32 bundles, each of 16 strands of wire,
.012" diameter).
*****
Figure 9. IGNITION CABLE (H.T.)
There is a range of 7 mm. (outside diameter) cables for the H. T. circuit. These
cables consist of a number of strands of tinned copper wire, insulated by means of
vulcanised rubber, with an additional sheath of either rubber, braided cotton, P. V.C.
or Neoprene.
The Neoprene insulated cable is specially recommended, as it affords the best
protection against heat, oil, petrol and water.
* * * * *

Lucas_Vehicle-Wiring_Training-Booklet_1964_Page_18_Image_0001.jpg

Figure 10. GENERAL WIRING
Now, we will consider the types of cable, which are needed for general car
wiring.
Three sizes of cable are normally used. All have PVC insulation, which is
impervious to petrol, oils and tropical fungi. In some cases, an additional cotton braiding
is also used.
Battery and Generator Main Feeds
44/·012 is suitable for currents up to 27· 5A.
If heavier cables are required, 65/·012 or 120/·012 should be used. These have
carrying capacities of 35A and 60A, respectively.
Other Main Feeds
We recommend the use of 28/·012 (that is, 28 strands of '012" diameter wire),
which is suitable for currents not exceeding 17·5A.
Remaining Circuits
It is unlikely that the current in any of the remalmng circuits will exceed 6A,
so the cable will normally be 14/·010 (14 strands of ·010" diameter wire).
However, the cable sizes we have recommended should be considered only
as a general guide, for the length and loading of each lead has an effect on the
voltage drop in the circuit. This must not exceed 10% of the battery voltage.
The voltage drop in the circuit is determined by the amount of current flowing
and the resistance of the cable. If the cables were increased in length, there would
- 4 -
be a corresponding increase in the resistance and ~he voltage drop of the circuit. A
point would ultimately be reached when the voltage drop in the circuit would exceed
the recommended limits.
Hence, heavier cables are used. By this means, the resistance of the circuit
is lowered, which in turn results in less voltage drop.
* * * * *
Figure 11. COLOUR CODE
In order that the various electrical circuits can easily be distinguished, the
Lucas Cable Colour Code has been introduced. Each circuit is wired in a different
colour. Further, the individual cables in each circuit can be identified, for the feed (or
supply line) has a single colour, while the switch cable has the same colour, with a
coloured tracer. Finally, all earthing cables are in black.
* * * * *
Figure 12. BASIC COLOURS
Eight main colours are used to denote the various car circuits. The present
Colour Code has. been authorised by the S.M.M. & T. (the Society of Motor Manufacturers
and Traders), and is thus based on the recommendations of the British Motor Industry.
However, for several years prior to 1961, another Colour Code was in use and, as many
cars with this type of wiring are still in service, we are giving details of both Colour
Codes.
No. Colour S.M-.M.T. Colour Code Old Colour Code
1 Brown Battery and Generator Current supply (or feed wire)
Generator and field circuit.
2 Yellow Overdrive (Sometimes Yellow and
coloured tracer).
3 White
Ignition circuit, and all units I~ition circuit, and all feeds,
controlled bl i~nition switch, w ich are essential when
(but not pro ec ed by fuse). ignition is switched on.
4 Green or Auxiliary circuits, controlled Auxiliary circuits, controlled
Light Green by ignition switchl protected by ignition switchl protected
by fuse '4' or 'A4 . by fuse '4' or 'A4 .
5 Purple
Circuits not controlled by Auxiliary circuits fed from
ignition switch, but protected ammeter, and protected by
}:,y fuse '2' or 'A2'. fuse 'A2'.
6 Blue Headlamps. Fed from Light- Headlamps. Fed from Lighting
Switch. ('S2' or 'H'). ing Switch.
7 Red Side and Tail Lamps. Fed from
Lighting Switch. ('SI' or 'T').
Side and Tail Lamps. Fed from
from Lighting Switch.
8 Black Earth Circuits Earth Circuits
- 5 -
Figure 13. CABLE HARNESSES
Lucas cables are supplied to car manufacturers in the form of a harness already
made up to suit a particular vehicle. This method has been adopted to speed up car
production.
However, as each harness has been designed for a particular model of vehicle, it
would not be practicable for every garage to hold a stock of harnesses in order to rewire
cars. It is more economical to renew the individual cables, as necessary.
* * * * *
Figure 14. WIRING LAYOUT
At first sight, the vehicle wiring layout probably appears complicated. So, we
propose to show how the wiring diagram is made up. We shall be considering the
electrical circuit in the following sections.
First, the charging and starting circuits, then the ignition system, and the units
controlled by the ignition switch. Next, we will show how to connect the units, protected
by fuse 2 (or A2). Finally we shall consider the complete lighting system.
* * * * *
Figure 15. CHARGING AND STARTING CIRCUITS
Let us see how the generator, control box and battery are wired up.
The generator has two terminals, 'D' and 'F', which are connected to the corresponding
terminals on the control box.
The 'A' terminal on the control box is connected to the ammeter (when .fitted),
and then to the starter switch. The circuit is completed by connecting the starter
switch to the battery negative terminal by means of a heavy duty battery cable ..
The control box (excluding model RB310 which is earthed via its fixing points)
and battery must be connected to a good earthing point on the vehicle.
*****
Figure 16. IGNITION CIRCUIT AND WARNING LIGHT
Now, let us consider the ignition system.
This is controlled either by a separate ignition switch or by a combined ignition
and starter switch, or an ignition and lighting switch.
- 6 -
The ignition switch has two terminals, the switch feed terminal is connected
to the cable from the 'A1' terminal of the compensated voltage control box (on current
voltage control boxes, the connection is made to either an 'N or 'B' terminal). The
other terminal on the switch is connected to the cable which comes from the primary
winding of the ignition coil, via the coil terminal marked' -' or 'SW', and hence to earth
through the distributor contact breaker, via the cable which is connected between the
coil '+' or 'CB' terminal and the distributor body.
The ignition warning light is connected between the control box '0' t~rminal
(terminal marked W/L on RB340) and the ignition switch.
This warning light performs two functions :-
1. . Its primary function is to indicate that the generator is in fact working, and supplying
current for charging, ignition etc., when the engine is running above generator
cut-in speed. (Above cut-in speed it is extinguished). It lights up when the
engine is stationary or when the generator is faulty.
2. It indicates, by lighting up when the ignition is switched on, that battery current
is being fed to the ignition coil and other ignition-fed accessories. It also
serves as a visual reminder for the driver.
The ignition switch in the diagram has three terminals, because it is a combined
ignition and starter switch. The third terminal is connected to the starter solenoid.
When the ignition switch is closed, current flows from terminal '1' (or'IG') at the
switch. It passes through the warning lamp to the '0' (or 'W/L') terminal of the control
box, and via the generator cable to '0' on the generator, the circuit being completed
through the generator winding to earth. The lamp, therefore, lights up.
When the engine is started, the generator voltage commences to build up, and
oppose the battery voltage. Eventually it equalises the battery voltage previously
applied to the lamp, and current will ce€lse to flow through it. Therefore, the light goes
out, and remains so, until the generator ceases to charge, and its opposing voltage falls.
Battery current will then pass through the lamp again and it will remain alight until the
ignition switch is moved to the 'off' position .
The complete ignition system is wired in white, as are also those units wh>h are
controlled by the ignition switch, but not protected by a fuse (for example, the stal:<:!r
solenoid).
* * * * *
- 7 -
Figure 17. UNITS CONTROLLED BY IGNITION SWITCH
(Protected by Fuse 4 or A4).
We will now consider the units, which are controlled by the ignition switch, and
are protected by fuse 4 (or A4).
The individual circuits are wired in green. For instance
Stop Lamp and Switch.
Reverse Lamp and Switch.
Flasher Lamps, Flasher Unit, Warning Light and Switch.
Windscreen Wiper and Switch.
* * * * *
Figure 18. UNITS PROTECTED BY FUSE 2 or A2
Then, there are the units, which are protected by fuse 2 (or A2). These receive
their supply via the ammeter (when fitted), from the Control Box 'A' (or 'B') terminal.
They are not normally controlled by the ignition switch.
Circuits include:
Interior Light and Switch.
Horns and Hom Push.
These circuits are wired in purple.
* * * * *
Figure 19. LAMP CIRCUITS
Finally, we will show how th~ lamps are connected.
The supply for the lighting circuit is received from the 'AI' terminal of the control
box. (Incidentally, when a current voltage control box is used, the supply is received
from the 'B' terminal or Ammeter). It is connected to the lighting switch, by a brown
cable with blue tracer.
All the lamps are then connected to the lighting switch. The headlamps and long
range driving lamp are wired in blue. The other lamps, controlled by the lighting switch,
(for instance, the sidelamps, tail lamps, foglamps and panel lamps) are wired in red.
When fitted as initial equipment, fog lamps usually take their current supply from
the side or tail lamp terminals on the lighting switch so that they may be automatically
switched off with the side lamps. Driving lamps are normally used to supplement the
headlamps at night time and as such should be controlled by the dipper switch so that it
can only be used with the headlamp main beams.
* * * * *
- 8 -
Figure 20. CABLE STOCKS
In order to carry out vehicle rewiring" it will be necessary to maintain adequate
stocks of standard cables and sundries. The following is the minimum selectiol1.You will
require.
1. Starter Cables.
(a) Supply Leads.
37/ .036 for Cars.
61/ .036 for Commercial Vehicles.
(b) Earth Leads.
16 x 16 x .012 for Cars.
32 x 16 x .012 for Commercial Vehicles.
2. General Car Wiring.
Three sizes are necessary.
44/.012 (for the battery and generator main feeds).
28/ .012 (for the other main feeds).
14/ .010 (for all other circuits).
NOTE:
In accordance with the Colour Code, the various circuits should be wired in the
appropriate colour. If, however, you do not have the complete range of coloured cables,
the leads may be identified by means of short lengths of coloured PVC sleeving.
3. Ignition Cables (H. T.)
H.T. Leads.
A number of 7 mm. cables are available, with a variety of coverings. The version.
with Neoprene covering is specially recommended.
4. Multi-Core Cables.
Cables are available with 2 - 7 cores.
steering column controls.
5. Cable Sundries.
These are essential for rewiring the
In order to carry out rewiring jobs, it is essential to maintain stocks of junction
boxes and cable clips. A selection is shown in our Catalogue 400E.
We must also mention two new types of connector.
(i) Lucar Connectors. These are 'snap' blade type connectors, made in phosphor
bronze, and they afford a more rapid and more efficient means of connecting
cables. Phosphor bronze is, of course, a better conductor of electricity than
brass.
(ii) Lucrimp Connectors. These mark an important advance on the ordinary
(bullet-type) snap-connector, for they have been designed for 'crimping' on to
the lead, with the aid of a special tool. (They do not require soldering).
* * * * *
- 9 -
Figure 21. REWIRING PROCEDURE
In service, you will encounter three different types of wiring jobs.
1. The replacement of a single cable.
2. The rewiring of a section of the harness.
3. Complete rewires.
These tasks will be performed more efficiently, if you heed the following
recomm endations.
* * * * *
Figure 22. REPLACEMENT OF SINGLE CABLE
When you replace a single cable, or add an extra accessory :-
(a) Use correct cable (both as regards size and colour).
(b) Connect to appropriate terminal . (See the appropriate wiring diagram).
(c) Keep wiring away from moving parts, for instance, the brake cables, and also
the 'hot spots' of the engine compartment.
* * * * *
Figure 23. PARTIAL REWIRES
When you are called upon to rewire a section of the harness, you should cut out
the damaged cables, while the harness is in position on the vehicle.
Then, new cables of the correct size and colour are connected between the appropriate
terminals. A terminal block or a junction box will probably be required. You
will also need to join the cables by means of snap-connectors. We specially recommend
the use of 'Lucar' and 'Lucrimp' connectors.
* * * * *
Figure 24. COMPLETE REWIRES
Finally, we will consider the procedure for complete rewires.
As we have already stated, it is not a practical proposition to keep every type of
cable harness in stock. When a complete rewire is needed, the old harness is removed
from the vehicle, and used as a pattern.
The harness should be placed on the bench, with a few locating pins to hold the
leads in position, while the new cable set is made up. The new cables are taped together
- 10 -
using PVC tape to form a harness of the same shape and pattern as the original. The
new harness is then fitted into the vehicle.
An alternative method would be to cut out the damaged leads and replace them
with cables of the correct size and colour, while the harness is in position on the vehicle.
* * * * *
Figure 25. CHECKING THE REWIRE
After the rewire has been completed, the complete electrical system should be
carefully checked before the vehicle is put into serVIce.
1. Battery
Must be at least half-charged, and in good condition. Check that the earth connection
is clean and tight. (Main battery lead should not be connected to the terminal
post for the time being).
2. Oil-Pipes
Check that oil pipes have been re-connected properly.
3. Switches
Must be in the 'off' position.
4. Cables
All leads must be properly connected. (Check with appropriate wiring diagram).
5. Battery
Negative battery lead is then connected, but not tightened. (The lead can then be
removed quickly, if necessary).
6. Ignition
Switch on the ignition, and start the engine.
7. Checking Electrical System
Checking the charging system, lighting equipment and accessories.
If everything is in order, tighten the connection to the battery negative terminal.
The vehicle is then ready for service.
* * * * *
- 11-
Figure 26. GENERAL
It will probably he necessary from time to time to check the electrical circuits.
From what has been stated, you will realise that failures in any of the electrical circuits
may be due to any of the following :-
1. Battery (Discharged or Defective).
2. Faulty Units (or switches).
or 3. Wiring and Connections.
Figure 27. THE BATTERY
* * * * *
The battery is the main source of electrical energy on the vehicle. A discharged
or faulty battery will affect the performance of the other units. So, do not adjust or replace
anything, until the battery has been checked. It must be at least half-charged, and also
in good condition, so that it can supply the high currents required for starting.
* * * * *
Figure 28. FAILURES DUE TO UNITS AND SWITCHES
It is our experience that many units and switches are replaced unnecessarily, for
the cause of failure can often be traced to the connecting wires and terminal connections.
Incidentally, while checking the circuit, you must remove all traces of oxidisation
from the terminals.
* * * * *
Figure 29. THE WIRING
All cables should be inspected regularly to insure that the insulation is sound or
unfrayed. If any cables have been replaced, check that the voltage drop is within the
recommended limits. Ensure too, that the cables are in accordance with the S.M.M.&T.
Colour Code.
* * * * *
Figure 30. FAILURE IN ACCESSORY CIRCUITS
The procedure for testing the Charging, Ignition and Starting Systems has been
described in previous sections of the Course.
Let us suppose that when you switch on one of the accessories, it does not function.
Aswehavestated,the cause of failure must lie either in the battery, the units and switches
- 12 -
in the circuit, or the connecting wires. Three checks have been devised, so that the cause
of failure can soon be established.
The important thing to remember is that all the accessory circuits can be tested
in precisely the same way. All that is required is a voltmeter with a suitable scale, and
sufficiently accurate to read to O.SV. A 20V scale voltmeter is suitable for checkingthe
normal 12V systems. However, you will need a 36V scale meter to test 24V systems.
* * * * *
Figure 31 STAGE 1- CIRCUIT CHECK FOR EXCESSIVE VOLTAGE DROP
Our first task is to find whether there is excessive voltage drop in the circuit.
(We are assuming that the battery is fully charged, and in good condition).
The voltmeter is connected across the battery terminals, the unit is switched on,
and the reading is noted.
Then, the voltmeter is connected across the terminals of the unit, and the reading
is again noted, when the unit is switched on. If the difference in voltmeter readings (the
voltage drop) is more than 10%, you should proceed to Stage 2.
* * * * *
Figure 32. STAGE 2 - CHECKING INSULATED AND EARTH LINES
Having discovered that there is excessive voltage drop in the circuit, we must
ascertain whether the fault is in the supply line, or the earth line.
A voltmeter is, therefore, connected between the battery positive terminal (+) and
the unit earth terminal (+). The current is switched on to the unit, and the voltage reading
is noted. The reading on the earth line is usually ZERO. (In view of the small voltage
readings, you will appreciate the necessity for using a good quality voltmeter).
The voltmeter is then connected between the battery negative terminal (-) and the
unit negative terminal (-). When the current is switched on again, the voltage drop should
be less than 10%.
If the voltage drop in either line is excessive, it proves that there is a fault in that
particular line. If, however, the total voltage drop in both lines (the insulated and earth)
is more than 10%, it will be necessary to proceed to Stage 3 in order to locate the causeof
failure.
* * * * *
- 13 -
Figure 33. STAGE 3 - CHECKING INDIVIDUAL LINES
For our next test we need a voltmeter with a wandering cable. The positive voltmeter
cable is connected to the battery positive terminal, while the negative cable is moved
in turn to all connections in the earth line.
Then, the voltmeter negative cable is connected to the battery negative lead and
the positive lead is moved to all connections in the supply line. The point where excessive
voltage drop occurs is then established, and you will be able to take the necessary action,
for instance, replace defective wiring or tighten terminal connections. .
* * * * *
Figure 34. CONCLUSION
The three tests we have described hold good for all the electrical circuits, for
they are really the 'Principles of Circuit Testing'. Let us just summarise the procedure.
1. Check for excessive voltage drop in the circuit. (Over 10%).
2. Ascertain whether cause of failure is in the supply line or the earth line.
3. Check line systematically and find where excessive voltage drop occurs.
You will then be able to take the necessary action .
* * * * *

Lucas_Vehicle-Wiring_Training-Booklet_1964_Page_19_Image_0001.jpg