Odd Electrical Issue (Climate control and some other dash stuff acting weird)

[genscripter]

The last few days, when I start my Jetta, the brake light stays on (even after I unset the parking brake), but the "brake" indicator light is dimmer. Also, my fan won't turn on and other dash accessories don't work either. The radio and headlights work fine. But climate control electrical is out of whack.

It only lasts a few seconds, but it seems to be increasing with every day. The odd thing is, I don't have any starting issues. Also, I can drive with this electrical problem and there doesn't seem to be any impact to power or drivability.

I thought maybe my alternator was not putting out the right amount of power, but I have a voltmeter installed in the cig lighter, and I'm getting 13.4-13.7 V usually.

I think it's a ground issue, so I'll check the battery terminals, and I'll check the grounds under the dash, but I changed out my heater core 2 years ago and I cleaned up and greased all my grounds so I doubt they have corrosion.

I also thought maybe it was my ignition, but I jiggled the keys while driving and that didn't seem to impact the electrical problem. I also thought maybe it was a vacuum pump issue (maybe the brake light is an indicator of low vac pressure due to a busted vac hose or weak pump), but I didn't investigate that.

Any ideas?

 

[Mongler98]

Not nearly enough volts to the battery. 14.4 is what these should be cranking out. Yea it will charge it, but not well.
Grounding issues are common but it sounds like you need to start testing at the fuse pannel to ground. See if you have a short.

 

[garciapiano]

On my car this brake light issue was related to a bad ignition switch.

 

[genscripter]

On my car this brake light issue was related to a bad ignition switch.

A few years back, I changed out my ignition switch using that clever steering-column-pull method. I don't think the replacement would've failed this early, but who knows.

The odd thing is, the weird brake light issue has mysteriously subsided on its own. I can't seem to reproduce the problem at the moment, so I can't even test where to begin testing. I'll keep driving it and see if the issue returns.