12-31-2014, 10:24 AM
Join Date: Jun 2009
Total Cats: 0
99 alternator going bad, or did I not make my voltage regulator correctly?
I have reached 130k on my 99 NB. As far as I know, it has the original alternator. I left me stranded last weekend - I had about 30 s notice before the engine died. I drove it home with an extra battery shunted in.
Running a DIYPNP with Cuadra alternator circuit on the proto area.
I cannot remember if I confirmed good voltage at one point with the PNP regulator, but I think that I did.
Now, I am getting 12.24 vdc out of the battery [new].
Running, I am getting 11.53 - with all accessories, it drops to 11.18.
Normally, I would immediately suspect that the alternator was bad, but...
How can I confirm that is not the fault of the alternator circuit?
1) To run it again with the original ECU to check alternator voltage output means MAF and IAT and possibly injector rail swap again. I like to reserve this pain only for my birthdays.
2) Or, I could buy a new alternator, swap it in, and curse when I learn it is the regulator. Or maybe it is the alternator after all.
Is there an easier way of confirming that the alternator is indeed going bad?
Perhaps, you will tell me that it is no question a bad alternator, but I want to spare my self the embarrassment of step 2, if there is a first check of the circuit that I can run.