Complete loss of electrical power

[StephenP]

Anyone come across this problem before. I ran the car last Friday and drove about ten miles. On trying to start it this Friday (30th) there was nothing when I switched on the ignition. No starter,lights,horn.wipers,semaphores dead. We have power up to the control box but when I switch the ignition on we lose it. I've take the earth strap off and cleaned it up and the chasis, checked the fuses but no joy. So if anyone has any ideas for me to try out I would be very grateful.

[David Morris]

Hi Stephen,

You have a high resistance connection somewhere. I suggest you start with the battery connections and work forward. I realise that you said that you have power at the control box, but I assume you were using a meter? This uses a tiny amount of power and any resistance in the various connections can be ignored. Try using a test lamp, this uses much more power and any resistance in the connections will be result in no joy in the bulb.

As so much of the electrics are 'dead', my guess would be immediately to go for a dirty battery connection. Go for a wire brush and don't be gentle when putting it back, a good tap with a spanner is always worth doing!

Best of luck!

David

[StephenP]

Thanks David for your useful reply. Today a mechanic came over and we carried on from cleaning up the battery earth terminal and carried on to the solenoid. We removed the terminal and cleaned them up ( split one nut oops).On playing around with the wires under the control box we had all systems go. Unfortunately we're still not sure what the problem was, but it's running at the moment. The worst sort of outcome really as we don't know what the problem really was. The trials and tribulations of running an old car. Thanks again for taking the trouble to reply,it was much appreciated, (we are not alone.)

[David Morris]

Hi Stephen,

Thanks for your reply. Always glad to help. The main thing is that you are back in action. Electrical gremlins are not confined to older cars. The wipers on my 406 stopped completely the other month. I only got them going by giving one of the multi-way plugs that seemed to feed the wipers a good 'wobbling', which was inconveniently tucked away right under the bulkhead.
Cars have got so complex, you need a laptop to even start diagnostics. I hope your mechanic didn't start on your Jowett by saying, 'where is the diagnostic plug? '

Any questions, and the Jowett community will surely help if they can!

David

[ian Howell]

I have encountered this type of problem before. Previously it was ultimately due to 'dry' joints within the control box.

On the back of the box, connections are made by means of brass strips rivetted to the backs of the terminal posts.

These joints corrode (not green, but dirty) and so lead to open circuits.

One way of curing the problem is to run solder into the joints after cleaning up all accessable surfaces. I have recently seen a control box which had received this treatment.

Also, MANY years ago, when I helped return a Bradford to the road, we found - after much searching and cussing - that one of the brass strips had cracked. Here again solder came to the rescue with a bit of thick copper wire to make sure.

This may help?

[Keith Clements]

A volt meter and circuit diagram should always be in an old car. Learn Ohm's law and where all the components are on the circuit diagram. Then finding faults is much easier.
JT already contains many experiences of electrical issues so use the search facility.

[David Morris]

Hi Stephen,

Oddly, we had exactly this problem ourselves this week on the green Javelin we are restoring, NKJ 352. It turned out to be the connections to the control box. We found the wires had corroded under the terminals. When we unscrewed the terminals and then re-tightened them, all was ok. I guess your statement in your post 'On playing around with the wires under the control box we had all systems go', showed that you probably had the same problem? The terminal post that gave us the same result as your loss of power was marked A1.

All the best,

David

[Alf Heseltine]

Stephen, another possible cause are the 'fuse holders'. They oxidise & cause poor contact with the fuses &
the problems are similar to yours. If you remove the fuses & clean up the fuse holders, remove the tarnish & verdigris
with fine 'wet & dry' burnish them until clean & bright, even if you are up & running it is still good to carry out
this service to prevent power issues in future.
Regards. Alf.

[Keith Clements]

Use a volt meter to see where in the circuit you loose the volts!
Connect one end of your meter directly to the battery earth terminal (either negative or positive depending on polarity of your system) with a wire.
Start by checking voltage at the battery terminal, then starter relay, then ignition switch input, fuse box (both sides), then ignition coil , then switch lights on .
If you have volts but no lights the problem is in the earth circuit. that is battery terminal, earth strap or any other return route your component uses to get its volts.
Note you can get volts sometimes but these disappear when current is being taken. This is due to a high resistance in the return circuit.
Use the meter on ohms to check this resistance. It should be less than one or two ohms.