Assuming this is correct, then:

10.6v when key is ON
0.5v when the car is running, but NOT charging
14.5v when car is on and charging

 

Was the 10.6V with the connector unplugged?

 

Yes. The the other two were taken with needle probe through the wire insulation. Do I need to take another reading with it plugged in?

 

No, I expected it was disconnected and just wanted to confirm. It will be about 0.5V connected.

I believe that you could connect a resistor between an ignition switched source and the L wire, with the BCM still connected. A resistor around 100ohms and 5W is the value I would try.

The reasoning is this. The BCM basically has a current limiting circuit that provides power to the L terminal. The alternator uses this current as the signal to start working, combined with it rotating once the engine is started. The rebuilders are using the wrong regulator circuit and their regulator circuit requires a higher current into the L terminal. So, adding the resistor would boost the current and "kick-off" the regulator without having to first rev the engine.

The problem is that I don't know if it will work. There is a chance it could damage the BCM, but I don't believe it will. The BCM output already gets shorted by the alternator so a short on that circuit won't damage the BCM. The BCM also has full battery voltage applied to that circuit (vehicle running and alternator charging) so a resistor also attempting to apply full battery voltage shouldn't damage it.

Of course, the better solution is to find an alternator that works. Unfortunately, it is somewhat of a crap shoot. An alternator that works for one person doesn't mean it will work for another. The only way to know is to get one with the correct regulator where you can confirm the regulator part number.

 

Lionelhutz, do you think the L terminal voltage is too low. Could it be his ignition switch is limiting the voltage? It should be about full battery voltage at around 12.5-12.6.


Mr. Sam

 

No, the circuit is in the PCM seems to provide about 10V with just the key on. The most likely problem is that the circuit limits the current too much.

I expect the battery voltage when running is provided by the alternator. To test it would require removing the wire with the engine running and alternator charging. But, the voltage sensing wire would have to remain.

 

I was afraid you would say that. The FSM says it should be 12 volts and says to just measure to make sure it is "near" there, no tolerance.

OP, would you be willing to go back to AutoZone and try another one? I don't think it is your car but the alternator.


Mr. Sam

 

I'll give it one more go from AutoZone, but if it doesnt work this time around I'll probably cave in and pick on up from the dealership...

 

Zags
Can you remove the plastic cover on the end and take a picture of the voltage regulator?

Bigdad

 

pm sent

 

Any update?


Mr. Sam

 

Well, I tried another from AutoZone and had the same results. So, I decided I'll just have to live with it for the moment. Dealership is crazy for asking $700+. Maybe if I get too tired of it I'll try a used Valeo from eBay.

I appreciate everyone's help, but I think I'm stuck for now.

 

Zags
If you pm me your name and address I will buy a voltage regulator for you to try out. If it works, you pay me the price for the regulator (less than $35.00). If it doesn't work just send me the new regulator.
Bigdad

 

Gee, you can't beat a deal like that. Go for is Zags. This guy is REALLY trying to help !!!

 

This forces me to pose the question. If this regulator is at the heart of the issue on the earlier C5s, is it just a matter of putting the correct regulator on a new unit? Would this also work for the higher 145a output alternators? Hmmm... what a tangled web we weave with this stuff...

 

This forces me to pose the question. If this regulator is at the heart of the issue on the earlier C5s, is it just a matter of putting the correct regulator on a new unit? Would this also work for the higher 145a output alternators? Hmmm... what a tangled web we weave with this stuff..

I'm thinking the same thing. That is why I'm looking for a 145a off of a 04 corvette, so I can put the other regulator in it and see if my 98 would like the 145a.

Bigdad

 

Why don't you try replacing the regulator as Bigdad suggested? Take a look at this post. It has info on the right regulators for both, 97-01 and 02-04. The price is around $30.

 

That is a very interesting idea... It seems that, in principle, it should work (as long as the 97-01 regulator could handle the 02-04 rotor)! Please, let us know how it goes

 

Finally got a chance to pull the back off of the alternator. Here's the regulator that's on it now. Text says VRPR1935. A Google search for which brings up a few dozen websites all in Russian.

Click for full size.
http://postimg.org/image/pbuq7hl6d/

http://postimg.org/image/mf5ianwtr/

http://postimg.org/image/ipqi1temd/


As Bigdad suggested, I'm going to buy a Valeo regulator, stick it in the AutoZone unit, and cross my fingers. I'll let you guys know what happens...

 

Check the link I gave you above on this post. It will take you to the right regulator for your 97 (Valeo Regulator 2542521B / M530). Let us know how it goes