Street side brake light not working w/ running lights on

[NicheVintage]

Our street side brake light is not working when our running lights are on. The curbside light does however. They used to work until this weekend. Any advice on how to fix it?

Thanks.

[4RXLA]

I take it the brake light works when the running lights are not on?

[TG Twinkie]

First; I'm assuming you have checked the bulb. Next; Clean the contacts on your 7 pin plug. Try wiggling the 7 pin pin and see if you can get the light to work. You can test it by turning on the turn signal, it uses the same filament in the bulb as the brake light. Also clean the bulb base if it looks good, both the contacts and the brass base, also clean the socket. If this doesn't work, it's time to get the meter out.

[extiger]

You may also want to check the TV fuses. Had a similar problem and after checking bulbs, cleaning contacts, testing connections several times, I checked the TV fuses and found one that was blown.

[dznf0g]

If I understand your situation correctly, I believe you may find a bad ground, and or corrosion, on that bulb socket. I believe your brake light filement is trying to get it's ground through the running light circuit. When the running lights are on you then have 12V on both sides of the brake light filement and thus no current flow and no light.

[moosetags]

The quickest thing to check is the previously mentioned brake light/turn signal fuse in the tow vehicle. Most modern TV's that came with factory installed tow packages have separate circuits for the trailer lighting.

Check this first as it is the easiest to diagnose and correct.

Brian

[dznf0g]

To clarify.....you have brake lights with running lights off and no streeside brake light when running lights are on, right?

That eliminates fuse and power supply issues, I believe.

[71safari]

Our 1971 Safari has a similair issue - when the running lights are on the signal lights don't work, when the running lights are off the signal lights work. We have limited ourselves to daytime towing... any advice appreciated.