S2 tail/stop lights

[StephenT]

I will try cleaning up more grounds. I think I have everything in the trunk/boot in pretty good shape but I will go over everything again.

Still don’t understand how the signal from the brake light switch can jump to the signal circuit.

Steve

[StressCraxx]

Another possible cause is how the bulbs are installed in the socket and if the socket wires are touching somewhere so the brake current is carrying over to the tail circuit. Could be mis-connected at the plug or a bare wire somewhere. Something is cross feeding.

[StephenT]

I was able to spend some time with the car today. I decided to start with the battery cable ground. To my surprise the connection at the chassis was only hand tight. So I removed the grounding cable all together and wire brushed the chassis to remove all grime and rust then reassembled everything nice and tight. There was no difference in the lighting issues.

When I reassembled the battery ground I added an extra wire and ran it to the trunk/boot area and attached it to the right light assembly. At this point everything started working properly. The brake light, turn signal and tail light all worked as designed and with full brightness.

I’m still amazed that a poor ground could possibly cause the results I was seeing.

Thanks for all the advice.

Steve

[Andy8421]

I’m still amazed that a poor ground could possibly cause the results I was seeing.

Thanks for all the advice.

Steve

Steve, if the housing isn’t earthed, then the current from the bulb that is being powered goes through the housing and uses the other bulbs in the housing as an earth. So as an example, if the rear right housing isn’t earthed and you power the brake lights, the current will go through the brake light filament to the housing, from the housing through the sidelight filament then through all the other sidelights to earth. It will also go through the indicator bulb and then to earth through the front right hand indicator. This leads to all sorts of weird symptoms, hence the best advice is always to check the earth first.

[StephenT]

Ok, I think I have the trunk/boot wiring sorted, to a functional point anyway. Using the extra ground wire I added where the battery cable attaches to the frame I made an additional grounding harness that attaches to two of the mounting studs at each rear light assembly plus the license plate light. All of the lights are working and bright. The only exception is the left front turn signal. I’m hoping that is just the bulb, I haven’t pulled that lens off yet to check.

I have not begun to deal with the headlights, that’s a battle for another day.

Thanks for the guidance,
Steve