I have recently been victim to frequent dead batteries though the battery itself is fine. I replaced the alternator and I’m still having a problem.
I finally discovered that my radio has been mysteriously coming on after I turn the car off. Left for several hours and the result is a dead battery. How do I fix this? My mechanic seems to have never heard of such a problem.
Sounds like you need a new radio, add a separate power switch or get in the habit of pulling the radio fuse when you get out of the car.
Electrical gremlins are one of the weak points of German cars.
Is turning the radio off not enough?
[i] Is turning the radio off not enough?[/i]
It depends on the radio. Most modern cars are likely to have some minor drain with the engine off. If it is an aftermarket radio, installed after the car was purchased new, then all bets are off. Many of those radios are problems.
If you are turning the power switch off on the radio and it is still turning on then it looks like you need to replace the radio or possibly the external control for it if you have that kind of setup.
Why did you replace the alternator?
If it is a bad radio, be careful what you replace it with, VW (oddly) wires some engine controls through the radio, believe it or not:
http://www.thecarconnection.com/tips-article/1007794_mechanics-tale-vw-heal-thyself
Those wacky Germans!
A fully charged battery will run the radio for days and still have enough power to start the car. The radio probably isn?t the problem; it could be a symptom though. I would start at the beginning and verify the battery is good. Also, have your mechanic check the battery cables with a volt meter. A bad battery cable can mimic the symptoms of both a bad alternator and a bad battery. If the battery is nearing the end of its life, replace it. You will have to soon anyway. Under normal circumstances does the radio work with the key out of the ignition? I seem to remember the Germans wiring their cars so the radio would work with out the key. If the key is needed the problem could be the ignition switch. Next, look up the fuse diagram in the owner?s manual and see what circuit(s) operate the radio. What else is on the circuit(s)? The next time you find the radio on, before putting the key in the ignition, look for anything else that might be on, especially things that draw a lot of amperage. In the end it could be the radio but there are a lot of other things to check first. BTW what is the model and year of your Volkswagen?
What year is your Jetta? Most old VW’s always had 12V to the radio even with the key out of thie ignition…I always hated that…in the cars I have had to deal with I always ran my own 12V SWITCHED power wire. Made life a lot easier in case you forget to turn off the radio