QuestionDave, This is the follow up answers to your questions about my Porsche 928 , Dave the answer to question 1 is, The loss of charge happens even if I dont drive the car, I can charge it fully and after a couple of days, the battery is completely dead again. As for question 2, When I park the car at any time the voltage meter is at it lowest point, it doestnt go to 12 volts untin I go on the expressway and I am doing 50 plus mph, then it registers 12 volts or above. As for question 3, There isnt any slack in the alternator belt, As for question 4, The battery cables are always clean and I have never had any corrosion on them at all. As for question 5, The voltage meter doesnt show charging at all if I am driving around the city, only if I go at least 50mph or better, then when I come to a stop, it doesnt register at all, Dave I would appreciate any help that you could give me, I have put over $8,000.00 in restoration in this car, I would love to drive it this summer, Thanks, Greg
AnswerHi again. Greg, thanks for giving me a little more context. When you spend a lot of more restoring one of these beauties, the last thing you want is a nagging problem.
The more I think about it, I believe you've got two problems left to sort out.
First: to find and correct the huge daily drain on the battery, here's the test:
1. Bring the battery back up to full charge (again!).
2. Satisfy yourself that no accessories, engine or trunk lights are on.
3. Disconnect the negative (ground) cable from the battery.
4. Connect one lead of a test light (either a light that glows whenever 0 to 12v is present or a multi-meter that shows a voltage readout when voltage is present) to the disconnected battery cable end and the other lead to the negative battery terminal that the cable was attached to.
5. If there IS a battery drain the test light will come ON. If there is no battery drain it won't.
6. Since your car has to have a drain the test light will be on...right? NOTE: If the car has accessories with memories like a clock or power seat positions, then the test light will glow dimly, because these memory items will cause a drain, but insignificant to your problem. I'm thinking the light will be glowing fairly brightly.
7. To find the drain, remove one fuse at a time and check the test light. If it goes out the items controlled by that fuse are suspect. If the test light stays on, replace the fuse, and remove the next one in turn, until all the fuses have been checked.
8. If the test light is still on after all the fuses have been checked, the problem is very likely in the wiring to the starter solenoid. There are two or three wires connected to the solenoid, sometimes sharing one attaching bolt. Remove one wire at a time until the test light goes out. CAREFUL, these are directly connected to the battery.
9. Assuming you found the area of interest, the correction is to trace the wire till you find the "short". i.e. the wire with the bare spot in its insulation that is touching something it shouldn't be.
Second: the other problem is the alternator/regulator.
We know the alternator works sometimes (over 50 mph), so I suspect the regulator is faulty. It's not cueing the alternator when to work harder, when not to, etc. If the regulator is separate (I'm thinking it it won't be, it'll be integrated with the alternator on the 928) it can be checked and replaced separately. Here's my advice. Wait til you sort out the battery drain problem and then do one of two things:
1. Take the alternator (and separate regulator if applicable) to your best auto electric specialist and have them confirm the problem and rebuild the unit.
2. Replace the unit with new or rebuilt. Unless you know that this alternator is new-ish and should be A-OK, just replace it so you'll have peace of mind it's perfect from this point.
I'd be interested in what you find...and I'd love to see some pictures. If you'd be willing to send me some, here's my e-mail: daves356@yahoo.com.
Looking forward to hearing your success story...
Dave
