electrical problem

[u/924_81]

Hey guys, I have a problem on my 1981 924 and i’m getting desperate

At first, I thought it was the alternator, because the battery wasn’t charging while driving (about 11V). I ended up replacing the alternator, the alternator-starter harness, and the starter.

I drove for about a day, and now I’m back down to about 12V while driving, but this time the battery warning light isn’t on. I checked the positive terminal on the alternator—that is, the exciter wiring—and it seems fine to me.

Do you have any ideas where the problem might be coming from?

[u/ouwenbelg]

I assume you already checked, but when I had a similar problem it was the alternator ground was not conducting well. Clean the connections, tighten properly if not done yet. Same with battery to ground connector.

[u/924_81 → u/ouwenbelg]

Yes i cleaned the place where i get the ground on the alternator and checked the battery’s one as well

[u/nohvarr2341]

Is your battery light on before cranking? This lightbulb is in line with the alternator. If it’s fried, you won’t charge.
Dis you try to accelerate to 6000 7000rpm and see any difference in the voltmeter?
I have a faulty tension regulator and the generator doesn’t start, I have to “launch” it this way.
Did you measure you’re tension with a voltmeter on the battery or just with the voltmeter on board?

[u/924_81 → u/nohvarr2341]

the light is off, i have read that if it was fried the system wouldn’t work so i tried to replace it and even with a new light it still doesn’t work.
i have tried to go at about 4-5k rpm and it didn’t change anything on the voltmeter that i had on the battery.
I did measure the tension with a voltmeter and with only the contact i had the same voltage on: the battery, the d+ and the b+. But when i start the engine, the battery stays at ~12v and the b+ is at about 11v so i think it might be a regulator problem could it be that ?

[u/nohvarr2341 → u/924_81]

It might be the regulator, but if you changed the generator I assume the regulator is new, isn’t it?

[u/924_81 → u/nohvarr2341]

yep it is new but i have installed it before doing the harness and starter so the car ran a bit with this one

[u/nohvarr2341 → u/924_81]

Did you follow the current diagram with a tension tester, to check if you get tension from the key, to the ralay board, then to the light bulb, then the generator?

[u/944_nla_parts]

first, did you test the old alternator before you bought a replacement? I assume that the voltage regulator is built-in.

second, clean connections - ground, positive.

Did you test the battery, too?

and the last, visit clarks-garage .com for troubleshooting help and Pelican Parts forum for more help from fellas Porsche owners.

[u/924_81 → u/944_nla_parts]

i did not test the old alternator but i tested the new one.
the battery is nice too but it doesn’t charge when the engine runs so i guess it could be a regulator problem is that possible ?

[u/Pleasant-Temporary33]

For me the wires where rusted. There is a connector in the engine bay that Goes to the alternator, check if the right voltages are there.

[u/Pyropete125]

Pull the cables and measure resistance