Hoping someone may have some suggestions. This weekend I took the truck on a trip to PA. My friend noticed that the brake lights weren't coming on. Today when I got back, I checked all fuses and everything was fine. I started checking voltage from the fuse panel back to the taillight assemblies. I found that the brake light wires were both worn out and separated from each other. I repaired the connection and they are working great. However, when I just moved the truck in, o noticed two things:

1) When I press the brake pedal, the dashboard background lights (the ones that light up the speedometer, fuel gauge, and temp gauge) come on. None of the parking nor headlights come on thoug.

2) The dome light no longer comes on when you open the door. It still comes on when you move the switch though.


Thoughts?

 

MOST likely, you have an open ground somewhere in the taillight assemblies. The brake light ground no longer works, so it's grounding "backwards" through the parking lights and dash lights. The parking lights are lighting too, but they are high-current bulbs so you just can't see them.

If I'm right, you should be able to access the stop light bulb, determine which side is supposed to be ground, and jumper it with a test clip to ground. (Remember: the body is probably NOT at ground; you may need to run a test wire back to the battery to be sure you have real ground.) If jumpering it to ground clears up the problem, you just need to find where the real ground wire is disconnected.

The stop light circuit doesn't share any connectors with the dash lights, and only shares the connector right at the taillight with the taillight circuit. So I don't think it's an "ordinary" short.

 

Wow, I would've never thought of that. Thanks much for your help. Will try and look at it tomorrow after work. Sadly I may not be able to look at it until next weekend with my crazy work hours.

 

Even more simple than that, check to make sure one of the bulb filaments hasn't dropped down and contacted the other one. Co-worker about 10 years back had a Corolla with the same symptoms, and one of the bulbs had failed internally and was backfiring that way.

 

I hope you didn't combine the tail light signal and the brake signal wires. If you look into the bulb connector, there will be 2 contacts. Those are the positive signals to the bulb for the tail and the brake. Those take a 1157 type bulb. I've seen people use an 1156 which is a single element bulb, and it cross feeds power to both systems. The white wire with black stripe is the ground signal fyi

 

Thanks, I was just reading about someone else doing that as well.

Thanks. I definitely didn't combine them. Thanks for the info.