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I had some problems fitting my heater back in behind the dashboard after cleaning it up and repairing the battery box. It was very difficult to lift into place. I had to use a short length of timber and squeezed it in finally.

 

Some months later I discovered that the engine would not switch off when the side and headlights were on. I assumed that the compressed wiring behind the dash was responsible. So I was able to live with that for a while and plan to lift out the instrument panel on a warm day this autumn and check all the connections

 

However on my return from our SDG Autumn run this week-end I tried turning off the ignition using the key, while the car was still moving on the open road, and it cut off the ignition instantly.

 

So when stationary with the lights on there is a rogue electrical supply to the ignition and when moving with the lights on the rogue supply is off.

 

Is there any one available to help with an answer?

 

Thanks Richard & H.

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Richard

 

When you finally find the source of your problem, consider installing relays and an 8 way fuse box in your car. I have fitted four in my TR3A, one for lights, second for horns, third for Alternator and fourth for Kenlowe fan.

One thing I do know is that the lights are so much brighter since fitting the relay.

BTW I owe my thanks to IAN C and his friend for the extra wiring diagram to suit these relays, so if you need it, and they have no objections to me passing it on, I will e mail it to you when I get home in 7 days time. P.M. me your e mail address if you go that way.

 

Dave

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My first guess and I emphasize guess would be a missing or loose ground on the panel. I have absolutely no idea why moving or stopped would make a difference unless of course your foot was on the brake when stopped.

Tom

Agreed. Most electrical faults are bad earths and this sounds like a classic one. The wiring on our cars is not particularly complex but there is enough to provide alternate pathways if you have a mix of poor and good connections to cause your volts to find an alternate lower resistance pathway. You can either spend a lot of time fault finding for the intellectual satisfaction of knowing which ones. Or spend the same or less time just cleaning up all your earth points. Start with affected circuits obviously.

 

MIke

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Checked it out on a short run this evening. When it was cold it all worked well and normal.

 

But arriving back at home. the same problem cropped up.

 

How can a warmed up engine make a difference?

 

Week end for heater out after the classic car run in Uckfield on Saturday.

Edited by Richardtr3a
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Incorrect assessment by the owner. I have discovered that it is nothing to do with the engine running. When stationary I have my foot on the brakes. So I rewired the brake light switch to the main loom with a short length of cable and new connections and cleaned up the brake light switch.

 

After some experimenting it seems as though the green/purple cable is the fault. If it is disconnected the problem has gone. When connected the engine will not switch off with the brake pedal depressed. The cable, 22 on the wiring diagram, only runs to the rear lights.

 

The indicators have been running faster recently so there may be something affecting both circuits. I will have to clean up the earths on the lights and look for any damaged cable. This may lead me back to the dashboard switch

 

Any further advice would be very useful.

 

Thanks Richard & H. ( who is attending Saltdean Lido open air pool dog day tomorrow.)

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Thanks for the tip Roger.

 

I checked the fuse box and all looked fine.There were no loose or damaged cables. So I took out the cables at 2 x A4 and cleaned up all the wires and contacts. I tested the ignition switch with the engine running and it worked well with or without the brake light switch activated. I polished the connecting strip and sprayed connection cleaner in the thread before fitting the screws back in.

 

This evening I cleaned up A3 as well. All is now back to normal but it is not clear what the defect can have been.

 

Well done Roger

 

Richard & h.

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  • 2 weeks later...

More progress.

 

I have been fitting new earth connections to the rear lamps. Now it is darker in the evenings I was able to spot that the front side lights come on when you press the brake pedal. After a lot of dismantling I found that the rear left hand bulb was lighting up on both filaments which ever supply was connected. So I assumed that when pressing the brakes and sending current to the brake filament I am therefore sending current to the sidelight circuit. I changed the bulb and all lights are working properly.

 

The ignition will now switch of with the side lights on and the brake light activated. I have not yet found out how the lights affect the ignition.

 

Does any one have any ideas? :)

 

Thanks Richard & H.

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With a dodgy bulb, power comes from the side lights through the dodgy bulb into the brake light circuit up to the brake light switch and via the switch into the ignition circuit keeping the engine running even when switched off, assuming the brake pedal is kept depressed?. I had this happen on an old vauxhall I used to look after for an old chap, I was scratching my head for a while until he told me he had recently changed a stop and tail bulb. Cheers, Bill.

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Richard,

 

Have you fitted a relay to control the ignition circuit?

 

If so the limited current draw to hold a relay is provided by the ignition lamp circuit. A simple test if the ignition is running on with the ignition off is to turn on either the cabin heater fan or the wipers. If the engine stops instantly then the (brown white?) wire from the alternator needs a diode to prevent the limited current flow through the ignition lamp keeping the relay energised. This was an issue that Morten and I both experienced with an ignition relay.

 

Alan

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Richard,

 

Have you fitted a relay to control the ignition circuit?

 

If so the limited current draw to hold a relay is provided by the ignition lamp circuit. A simple test if the ignition is running on with the ignition off is to turn on either the cabin heater fan or the wipers. If the engine stops instantly then the (brown white?) wire from the alternator needs a diode to prevent the limited current flow through the ignition lamp keeping the relay energised. This was an issue that Morten and I both experienced with an ignition relay.

 

Alan

Ahhh, this explains it! I can't turn of the engine with ignition key, but it isn't a problem because I have a "hidden anti-theft" kill switch in the wire to the coil. Out looking for a diode then ;)http://www.ijonsson.se/tr2/photos/el/wiring_mod.jpg

EDIT: No diode in the shelf, would changing to a LED lamp instead of an ordinary filament bulb for ignition lamp work as well?

Edited by ijonsson
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Hi Bob

 

I am very careful with earth connections and have fitted a number of extra points. The engine has one on each side and there are a number behind the dash connected to one place on the heater support. Each back light has a single earth. But they do need cleaning a lot, and my car does not get wet often but there is still corrosion.

 

When I had the lamp in my hand and touched the earth to the body and a live feed to either terminal both filaments would light up. I replaced the lamp in the light base with a spare and it worked properly immediately. The chrome edge is worn so I have ordered a new unit and hope that it will be better made than my existing one.

 

I was about 1/2 an hour away from calling out a specialist old car electrician I am sure that he would have found it much quicker than me.

 

Roger, Thanks for the wiring diagram I have had it printed on heavy paper and it is easy to read.

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