This seems to be a perpetual problem with most of the new/reman alternators (have a newer 86-96 CS unit, FWIW). The last few Ive put in have always has the exciter go bad after a few months.

The current one hasnt had a properly working exciter for at least four or five years. Getting the alternator to work is down to the luck of the draw. Sometimes the starter makes enough ripple to energize it. Other times I have to let the car sit for a half-hour until the cooling fan motor comes on, at which point the alternator comes on as well with the ripple from the fan motor.

I assume this is a common problem with this series of alternators? Are some of the aftermarket ones like those from quick start any better? Is it possible that theres a wiring issue that does it?

 

I looked into this some more, and I was a bit mistaken as to how these work. They actually use duty cycle regulated field coils to control the voltage output. Any time theres power, the regulator switches the field coils at 400 Hz, and varies the duty cycle to control the voltage output. I believe it starts out at 10%, and then after startup and a short delay, it begins to vary the duty cycle to regulate the voltage.

So that begs the question of why does it decide to work when its running and an accessory like the fan comes on, but not at key-on? The field terminal has power, and the resistance of the circuit isnt too bad. But, could the small ammount of resistance that is there cause problems? Or is this just how these types of regulators fail? Just wonder if the resistance thats there in the "F" terminal could make the alternator think that the system voltage is low when its not.

 

The wire to the F terminal should have straight ignition switched +12 volts to it.

If using an idiot light that wire goes to the L terminal.

To get better voltage control run the S terminal (large one) to the battery via heavy gauge wire. Otherwise the alternator will sense the voltage internally at the output terminal.

GM used them in various vehicles both using and not using the S terminal.

RBob.

 

loose connections inside the factory wire harness plug will also cause problems..

I use a pick to work the metal connectors on the female plug side a lil tighter..

 

Im only using the S and F terminals, athough I did run a wire to the L terminal for future hookup to a PCM that can use the input when I redid the wiring, but its not terminated to anything at the moment.

I tried supplying +12 volts straight to the F terminal to energize it, but it still does nothing, so Im thinking its just another dead alternator. Still seems odd that they all die the same way, by failing to energize the field windings. Since they seem to have such a short life, Im probably just going to pop a new v-reg and brushes in it.