I've got an 88 240 that had a bosch 80amp until about a month ago I killed it with a big mud puddle. It would charge at idle sometimes but the more rpm I gave it the weaker the voltage it put out. 13 at idle, down to 11.9-12.3 at higher rpm. I had the alternator tested and it was found to be bad so I replaced it with a 740 100 amp. I also replaced the battery, b+ and d+ wires and got good voltage around the block on her first run but then I lost power again. I've tracked down the problem to the exciter wire, but I'm stuck. It only puts out ground, I know (er think I know) its supposed to be ground when the key is off but 7-9 volts with the key on with the battery bulb illuminated until the motor is running and alt charging. Problem is I only get ground. The bulb does not illuminate but it is not burned out, I've swapped bulbs and checked voltage at the gauge circuit board and it's still ground. As a dumb test I disconnected the exciter wire from the alternator and fed it 12 v to see if it would illuminate the bulb but it didnt. When I swapped ends and hard wired the alternator d+ exciter wire to the positive battery terminal my voltage jumped up to 14.08 telling me the alternator is working like its supposed to. (When redneck rigged together).
Dumb questions:
Is it in the ignition switch? This is a gambler 500 car and the switch works fine otherwise so I'd rather not replace it, could I just run a new exciter wire from a keyed hot source off the fuse box or does the exciter wire need to go to ground when it's off like factory to not drain the battery?
The studious reader can tell I have just enough electrical knowledge to be dangerous and that's exactly why I'm in the pickle I find myself in.
Dumb questions:
Is it in the ignition switch? This is a gambler 500 car and the switch works fine otherwise so I'd rather not replace it, could I just run a new exciter wire from a keyed hot source off the fuse box or does the exciter wire need to go to ground when it's off like factory to not drain the battery?
The studious reader can tell I have just enough electrical knowledge to be dangerous and that's exactly why I'm in the pickle I find myself in.