QuestionI have an 1985 318i BMW w/220,000 miles. I bought the car 6 years ago and replaced the alternator, radiator, etc. I went away to college 4 years ago and only drove it once in a while but had my parents start it and maintain it. Just recently someone was driving it, and the radio went out in the middle of the intersection and then the car suddenly died and would not restart.
We bought a new alternator and bench tested it before installing and it was good along with the battery. We just replaced the alternator last week and upon driving it again the car did a similiar thing, the electrical system went out starting with the radio and then everything in the car shut down and the car turned off. I am afraid it may be an internal electrical problem that may be difficult to find and fix. I appreciate any help.
AnswerYep, this is most likely a complex electrical problem.
start with the easiest things and then get more serious.
first, check the battery terminal and the connection for the ground to the chasis, if you see ANY corrosion or rust, sand or scrape it off and cover it in petroleum jelly.
next, go to the grounds under the dash and in the engine bay (check the engine ground strap). Then take a look at the positive lead that goes to the fuse box, put a voltmeter on it and see how many volts it's dropping (during cranking).
the fact that everything turned off at once implies to me that it's a bad ground, or severed/shorted wire somewhere. you need to have a voltmeter and be ready to do some tests next time the problem comes up. It's impossible to diagnose a problem that isn't showing it's ugly face.
-cheers
