TR3 electrical problem

[Richardtr3a]

This must be one of the most unusual problems on the forum.

 

My car is starting and running well. But at the International a new problem turned up.

 

If the headlamps are on and I turn the ignition key to "off" the engine will not stop. Turn off the headlamps and all back to normal. How is the coil getting power?

 

Please help.

 

Richard & H.

[Icarus60]

Richard

The light switch is supplied directly from the battery and is always live on the input and the output is switched to live in the side and head positions. Possibly the lights switched live is for some reason contacting the switched/output side of the ignition switch and is powering the ignition circuit at all times the lights are on, including when the key is in the off position. Could be a loose wire behind the panel?

Sounds like a job for a man with a meter.

Regards

Rog

[Lebro]

+1

 

Bob

[EdwinTiben]

Looking at the wiring diagram, the headlights are not directly connected to battery, but have their feed from the control box.

 

My guess is (based on a similar problem i had with my tr2) that theres a feed bridge in the ignition switch from the wire of the light switch.

 

with the light switch on, the feed flows from lightswitch through your ignition swith which feeds the coil, instead of the wire of the ignition light, see the orange arrow.

 

 

 

 

http://www.advanceautowire.com/tr24a.pdf

Edited August 2, 2017 by EdwinTiben

[RobH]

If the short was there Edwin, the action of the light switch would have no effect because that point is always live. Richard tells us the engine stops if he turns the headlights lights off, so the feed must be coming via the S2 contacts on the light switch. It also depends on whether any wiring mods have been done on the car of course - there might be things there which are not on the wiring diagram.

 

It would be useful to know whether it happens on both main and dip beam and whether it is possible to start the car with the lights on but ignition off. (probably have to manually operate the starter solenoid to check that)

Edited August 2, 2017 by RobH

[BlueTR3A-5EKT]

tongue in cheek.....

Triumph were experimenting with headlamp 'on' warning devices to make them error proofed against a flat battery - what better than you not being able to stop the engine unless the headlamps are off.

 

Peter W

[RogerH]

+1 Rob,

the output of the light switch is not connected to any part of the ignition circuit so unless there are wayward wires the problem should not exist.

The input to the light switch has a constant +12V but that does not affect the ignition.

If the ignition switch had a short then the problem would exist with the lights off.

 

As Rob states a clearer explanation of any 'add-on' wiring is needed.

 

When I got my car finished in the late 90's my son accidentally found that if he pulled on the headlight flasher stalk the ignition red light would come on.

Press the rubber t^t on the solenoid started the engine. Have a look around your main beam switch/circuit.

 

 

PS - just checked the 4A and the above problem has gone. Can't reproduce Ricards fault on my car.

 

I also agree with Pete - you do need a light warning alarm. What better than the engine running.

 

Roger

Edited August 2, 2017 by RogerH

[EdwinTiben]

Hi Rob,

 

You are correct with the constant feed from the light switch. of course there can be extra wires

[Richardtr3a]

In a quick burst out to the garage this evening I tried to remove the ignition key switch. It would not budge so using a torch and my left hand I ran my fingers all around the back of the switch.

 

This must have moved a suspect cable because the problem has vanished. The ignition key turns off the engine with the lights on or off.

 

Recently my heater was very difficult to fit, high enough, in the correct position when I tried to push it to allow for the two supports to slot into place. While I was struggling to make it fit, I must have compressed some cables and created a problem.

 

Why are those rubber flow and return pipes so tight against the scuttle.? I have the fancy rt.angled ones as well.

 

Richard & H

[RobH]

Its maybe not a good idea just to leave things there Richard - if you have a wire which is loose enough at the back of the dash to be moved accidentally with your fingers, then you have a potential for a worse short-circuit with resulting damage to the loom, or even a fire. Best to be safe and have a good look at things back there to make sure that eveything is secure, properly insulated , and that a short isn't likely to happen.

[Richardtr3a]

Thanks for the advice.

 

I will remove the heater and use a short length of pipe to join the two flexibles.

 

So back out to the garage tonight.

 

Richard & H.

[billy l]

I had a similar problem on an old vauxhall that I used to look after for an old chap, with headlamps on and brake pedal pushed the engine would not switch off, the stop and tail bulb had an internal fault so with power to the bulb from the lights back up to the stop light switch and through the ignition switch to the coil, I was scratching my head for a while until the owner said he had recently changed the S&T bulb. Cheers, Bill.