10 replies to this topic

[mark clark]

I have a problem when I turn the ignition on - the tail lights come on, even though the headlight switch is in the off position. How do I go out about fault finding this issue? (Car is an 89 Mayfair)

[JBW]

Are you sure its the tail lights, not the rear brake lights ?

Had a recurring problem a few years ago, which was always the thread for the securing nut on the brake switch being stripped.

[KernowCooper]

As above, check its not the brake light switch stuck? its at the top of the pedal, to check pull one of the wires off, if they go off then replace the wire you removed and flick the switch centre pin with a small electrical screwdriver, possible its working ok but adjusted down to far towards the pedal, unscrew it as required if thats the case.

Edited by KernowCooper, 21 January 2017 - 11:41 PM.

[mark clark]

Should've thought of that first off! (palms face!!!) Thanks people. Won't be able to check until the end of the week, but it makes perfect sense.

[mark clark]

Haven't had time to check my issue until recently. Replaced the brake switch and still have the same problem.

[KernowCooper]

take the wires off the brake light switch do the rear lights go out ? if so the switch needs adjusting back towards the driver as it not allowing full travel on the switch to break the contact.

[mark clark]

The lights did go out when I removed the wires from the switch. I also removed the switch from the pedal with the wires still attached and the lights were still on. Surely they should go off when there's no pressure on the switch? It seems like the switch is operating the reverse of the way it should.

Edited by mark clark, 26 April 2017 - 01:09 PM.

[tiger99]

Because the switch must be OFF when there is no foot pressure on the pedal, and ON when the pedal is anywhere from a few mm down to all the way, the switch is arranged to be pressed by the pedal return spring when the pedal is UP and released when the pedal is DOWN. So your switch action appears to be correct. It is a push to break switch.

 

It should be set up so that the pedal is pushing it when UP and releases it when anywhere except UP. I would aim to have it switch at 5mm to 10mm of pedal depression.

 

I hope that helps.

[gazza82]

The lights did go out when I removed the wires from the switch. I also removed the switch from the pedal with the wires still attached and the lights were still on. Surely they should go off when there's no pressure on the switch? It seems like the switch is operating the reverse of the way it should.

 

While it is out of the holder, do the lights go out if you press the switch button in? ....

[mark clark]

Sorted! I thought I was going mad that I couldn't wrap my head around something so simple.

There's some play in the brake pedal and it seemed the switch plunger wasn't long enough to make contact with the pedal, even with the new Lucas switch. As it happens, I found another old switch in the door pocket. I've just fitted it and it's all worked perfectly first time.

All the switches worked electrically, so I'm not sure whether the spring affecting the plunger within the problem switch was worn, or why the 2nd (brand new Lucas switch) behaved in the same way. Maybe poor quality of modern parts?

Anyway, thanks for all the advice and just to let you know I wasn't doubting any of the advice, just my own sanity!!!

[JBW]

Pleased to hear you've got it sorted.