Brake lights turn on dome light and shut off map lights

[iangoround]

So here's an interesting one...when I press the brake pedal my dome light turns on. If I have the map lights on, pressing the brake pedal shuts the map lights off and turns the dome light on. And none of them can be turned on by the dimmer switch.

So I figure the brake light circuit is backfeeding down a ground for the interior light circuit, but where in the car are those circuits close together? Could it just be a bad headlight switch? Just looking for ideas as to where to start hunting.

[black86glhs]

Have you checked to see if your connector is melted or warped?

[iangoround]

Not yet. I'll start there I guess.

[black86glhs]

What you said sounds like what is happening, to me. I was going to say backfeed through the ground when I read it in your 1st post. Unless someone else has another idea.

[marc]

The map, dome, and brake lights all ground in the left rear corner on a Daytona. You didn't mention what car you have, but they are probably all similar. I would suspect this first.

You may have a bad headlight switch also because your unable to turn on the dome lights from the dimmer switch. But this would be totally unrelated to the back feed problem with your dome light.

[iangoround]

The map, dome, and brake lights all ground in the left rear corner on a Daytona. You didn't mention what car you have, but they are probably all similar. I would suspect this first.

You may have a bad headlight switch also because your unable to turn on the dome lights from the dimmer switch. But this would be totally unrelated to the back feed problem with your dome light.

This is on my 86 Turbo Z, so I'll check there first. I did at one point have to replace a tail light socket that had a bad ground. If that crimp connection came undone it could be part of my problem. Thanks for the tip.

[iangoround]

Fixed it.

So the brake light/dome light fuse was blown. Not sure why. Yet SOMEHOW the brake lights still worked. Also not sure how. I'm guessing the little bit of current on going down the ground side of the brake lights was enough to make the LED dome light flicker, but when I opened the door there was a better path for that current to ground than through the dome lights. I replaced the 20A dome/brake lamp fuse and everything works normally again.

So, symptoms resolved but am not sure why the fuse blew in the first place. Maybe I jostled something down there when I replaced the turn signal flasher.

[Dr. Johny Dodge]

there is a switch for the interior lights on the hatch latching mechanism in most of our cars

this switch can play havoc sometimes too

[black86glhs]

Wow. I almost said look for a common ground, but thought there is no way they would all share one. Boy was I wrong (not surprising).