Electrical gremlin - brake lights and front side lights

[scotty57]

A funny thing happened on the way to the shops.............

As I was getting the Stag out the garage I noticed that when I used the footbrake the front side lights came on but I cannot see any connection on the wiring diagrams - any ideas chums ?

[davidf]

Probably an earth problem on the rear/stop lights. Instead of the current going direct to earth, it goes through the sidelight filament of the rear/stop lamp then through the front side lights.
You will probably find that if you brake with the side lights on, you will get no rear light.

[TR5convalescent]

I had this with an Audi 80 about 30 years ago. I cured it by running individual earth leads from every bulb holder to the bodywork. It took an age and was a pain in the neck!

Good luck.

[404ROD]

I have this same problem at the moment. I only noticed it after I switched to LEDs(not the headlights) and wondered if this was the cause. I will have to look at the suggestion that when the side lights are on braking will turn the rear lights off.

Rod

[scotty57]

Update :
I have added a better earth to the rear stop lights on the n/s because that is where the o/s earth also terminates. When the brake is applied now the front side lights still glow but not as bright as when they are turned on properly. There is no effect on the rear lights when the brake is applied. Could the problem be poor earths at the front side lights ?

[davidf]

Update :
I have added a better earth to the rear stop lights on the n/s because that is where the o/s earth also terminates. When the brake is applied now the front side lights still glow but not as bright as when they are turned on properly. There is no effect on the rear lights when the brake is applied. Could the problem be poor earths at the front side lights ?

I don't think the problem can be with earths at the front - the current is taking that path from the rear lights.
If you have a volt meter, check right on the actual bulb casing of each of the rear lights - I am sure you will find a small voltage on one that is not earthing properly.
It may be the contact from the bulb to the socket, rather than from the socket to the bodywork.

[Guest]

Dodgy earth most likely, just try and check/clean all the earths for each light. Very strange things happen with iffy earths.

[404ROD]

I have just has the job of replacing my radio aerial on my nearside rear wing and thus had to remove all and sundry from the boot. Whilst working on this I discovered that one of the wire connectors, of the wires that lead into the boot lid and thus illuminates the number plate, had come apart. On reconnecting this I have now solved the problem of the front sidelights coming on when using the foot brake. I do very little night driving and therefore had never checked whether my number place was illuminated or not.

Rod

[DJT]

I have just has the job of replacing my radio aerial on my nearside rear wing and thus had to remove all and sundry from the boot. Whilst working on this I discovered that one of the wire connectors, of the wires that lead into the boot lid and thus illuminates the number plate, had come apart. On reconnecting this I have now solved the problem of the front sidelights coming on when using the foot brake. I do very little night driving and therefore had never checked whether my number place was illuminated or not.

Rod

Hopefully they we’re working on 11th April when it was MOT’d.....

[404ROD]

Hopefully they we’re working on 11th April when it was MOT’d.....

One does wonder as the MOT is obviously carried out in daylight and those two boot lid lamps are hardly up to much to be honest. Mind you I have only recently noticed the problem so they may have been working OK at MOT time.

Rod