Out of seemingly nowhere I have an electrical issue!!

It is an intermittent issue. It happened a few times in the winter time (everything came back on within a few seconds.) But now it's all staying off.

For some odd reason, there's a short that kills my dash, climate control, headlights, turn signals, and 9v outlets. Car runs fine, radio works, windows work, alarm works, but for some reason everything else is dead. Like I said above, it's happened a few times before, but only when starting the car, and it would all come back within a few seconds. This made me think I had a faulty ignition switch, so I replaced that (and the airbag didn't go off in my face thank god.) Problem persisted.

I read something online about there being this battery control unit that diverts power when it senses your battery running low on juice just so you can still start the car. I replaced the battery, and after driving it for a few minutes everything came back on! So here I am thinking I fixed everything with a simple battery. Then today (about 2 weeks after replacing the battery) I was getting off the freeway and decided to turn off the AC. As soon as I pressed the off button, the dash went dead, and I couldn't turn the AC on again. Same symptoms as before.

I called up a buddy with a voltmeter and had him test my battery/alternator/grounds. Everything checks out. So now I'm looking into a control unit. ECU? That battery control unit? I'm completely stumped and have no idea which direction to move in now. I'm hoping someone can lend some knowledge out my way!!!!

 

Check the voltage at the battery terminals with your buddy's meter while the car is running. Should be around 14.2v. Could also do a load test on the new battery. Could be defective. Charge up the battery then hit with a load test to see if it is being properly charged and retaining the charge. You didn't mention the mileage on the car but it could be the alternator failing. I'm guessing you don't have maintenance records on the car.

 

We checked the terminals with the car off and with it running. Everything seemed fine. Battery, grounds, alternator and all.

I have not performed a load test on the battery. I'll try and give that a go.

The car has 154k miles, and I do have all the service records believe it or not.

 

Just checked the resistance and it all checks out.

Since both the dash and climate control go out at the same time, is there a control module somewhere that might be disrupting the circuit?

Does anyone know where I can find a diagram that lays out wiring for this particular part?

Any help at this point would be extremely useful.

 

Doing a load test isn't a resistance test. It requires a special tool that actually puts a load draw on the battery. I am suspecting that the alternator is defective. You should get the car scanned for faults using a VAG Com scanner and then look up the codes. Also regarding the situation being resolved after changing the battery, sometimes a hard reboot of the car (disconnecting the battery for a time then reconnecting) will reset codes and minor faults for a short time but they often return. Get a scan performed.

 

I decided to take it to a mechanic, and believe it or not it was a bad ground on the fuse box.

It's always the easy solutions that have us scratching our heads, right?

Either way, she's back on the road!!!

 

 

Good job. Often the most important tool in the box is perseverance. Glad you got it resolved. +1 Clancy.

 

Good catch... So often we focus on the plus side of the electrics, and forget that the other side is equally important.