10/4 low tension wiring

[nigel jarrett]

Sorry all its me again ,I have just fitted a new 12v coil in place of the ballast resisted coil on the car.i went to fit a new low tension lead between the coil and distributor ,when i looked at the distributor there was two wires fitted in the original loom one from the coil to the distribution,then one from the distributor into the loom and back towards the bulkhead ,the wiring diagrams only shows one wire has anyone any ideas

[Keith Clements]

Could be rev counter or disabling switch or electronic ignition , assuming it is not an original loom.
But if it is you need to trace where the wire goes my guess would be the ignition switch.
What does the wiring diagram say?

[Tony Fearn]

Sorry, can't help.
Don't know much about car wiring.
The switch side of Mary Ellen's coil has a couple of extra wires which connect add-on auxiliaries to the ignition switch.
The contact breaker side on the coil has only one wire to the brass nut on the side of the distributor.
Tony.

1935 Wiring diagram.jpg

[Keith Clements]

It is unlikely the second wire originally went to the distributor. Only distributors with electronic ignition need any other wire apart from the one that goes to the CB terminal on the coil.
The electronic rev counter sensor wire is usually taken from the CB terminal on the ignition coil.
When a student in Liverpool I also disabled the ignition by breaking the wire from the CB terminal to the distributor with a concealed switch. This might confuse the guys who would try to hot wire the car to the ignition coil.

[nigel jarrett]

Thank you all for you input .It looks like the original loom still all in braiding the two wires are in the braiding and are joined together at the terminal,it's still the original ignition set up and no sign of any isolator switch Tony the wiring diagram will be very helpful thank you

[Keith Clements]

Is the ignition coil near the distributor? I suspect the wire on the ignition coil has been swapped for that on the distributor .
The primary coil (marked SW on old coils) on the ignition coil normally connects to the ignition switch via a ballast resistor, if you have one, and the other wire to the primary (SW) terminal connects to the starter solenoid output that also goes to the starter motor. This is so that you get the 10v or so that the battery pushes out when you are starting the engine rather than the 8v you would otherwise get via the ballast resistor. An ignition coil designed for use with a ballast should not have 12v attached to it .
The secondary or common terminal (marked CB) should be connected to the distributor. Modern coils are marked - and +.

Note that if you have a modern coil it will expect to be negative earth not positive like on most Jowetts. So the terminal marked - would be CB if negative earth. Thus your spark will (probably) be going in the WRONG direction if you connect the positive or plus signed terminal to your ignition switch or ballast resistor or starter solenoid. So you must check.

This has been discussed on JT and in the Jowetteer previously.
I am quite surprised your car started in the previous configuration.

[Tony Fearn]

Hello again.
This might be a more apt wiring diagram.
You may have to access JIS to be able to see it in the Gallery if you can't see it from this post.
At least it's for a 10hp albeit a van.

THis link is not as exact viewforum.php?f=95
as the original link was lost in the migration in 2019
gallery2.php?g2_itemId=2188&g2_imageViewsIndex=1
Tony.

[Keith Clements]

You do not need to be logged into Jowett Internet Services but you do need to be logged into JowettTalk and have a valid session with Jowett Gallery and your JT registered email must be same as in club membership list. The page you see when you login will tell you all this. Nigel should have no problem.

Note none of the diagrams show a ballast resistor so were any Jowett fitted with them?

[nigel jarrett]

I managed to purchase a instruction book for the Light car at Harrogate and looking at the wiring diagram for the 1936 it looks like this other wire goes back to the battery isolation switch,so I take it that when the battery is isolated the wire is put to earth as a security back up to stop the car being hot wired

[Keith Clements]

If the battery is isolated how does a hot wire get power? Note that electronic rev counters need a wire off the CB wire to operate. Some battery isolators have a fused bypass to keep clocks going. Having a wire going via a switch to either earth or live would disable the ignition as it would take either the CB or the coil respectively out of circuit .
Anyhow when at Liverpool University in the 60's we had a switch on the petrol pump wire that acted as a confusing deterrent. The car might start but would shortly stop. We also removed the rotor arm for prolonged stopovers. Even so we came out one night to find the car had disappeared. We were picked up by police for acting suspiciously. Eventually the police accepted our story and they found our car in Sefton Park. The thieves had pushed the car half a mile before abandoning it! Because we studied at the University Nuclear Reactor facility the Mini Van had Radioactive warning stickers on it. Great for having an escorted passage through the Mersey tunnel.