Diagnosing Power Problem

[viparz]

You have probably heard of this problem a million times before but I need help. My battery is draining while driving. At first I thought it was the stereo but I disconnected it all and still have a problem. I know it is not the alternator, as that was my original suspicion and I have already forked out for a new one. The charge is reading at about 12.5 volts over the battery when the car is running. My starter motor is on the way out (could this be draining power) I say this because on long country drives I don't have a problem, but after a few continuous short city trips, my car will not start. Headlights, indicators etc all work, just will not start. Also my headlight fuse gets very hot, could this be the problem. Any ideas for finding the problem, I have spent too much time and $$$ trying to fix this. HELP!

[Gav240z]

Could be the voltage regulator in the 240z there attached to the drivers side of the engine bay i believe.

I can't remember if yours has a thermo fan in it or not?

If so i had major headaches with a thermo fan unit in my old 260z killed 3 alternators. That's why in my current 240z i have left the old clutch fan.

I agree i don't think it's your stereo however one night while driving home my car almost shut off while i had the headlights, wipers, stereo and heater running , but it was a easy fix as the alternator belt itself was too loose from previous work i'd done in the area and I needed to make it that bit tighter.

See when it was under a large load the belt was obviouly just slipping and not charging the car.

Other possibility is your battery is on the way out. But before replacing it check the other things, also you do know you can put distilled water to top up each resevoir at the top of the battery?

If the level is below the (electrodes) i believe there called then it will cause problems with charge.

Can't think of anything else right now unless it's a short somewhere.

[MikeW]

Originally posted by Gav240z

Could be the voltage regulator in the 240z there attached to the drivers side of the engine bay i believe.

When my VR went bad recently the voltage on the battery with the car running was something like 17 volts. I think you normally expect to see something like 14 volts.

I think I'd just take the car to someone who can diagnose the charging system. Places that sell batteries will often do that for free.