Bill Curlee

If he had the wrong alternator as the orgional one and the parts place matched it up with the same one,,,,,,,same issue. Its a thought. My guess is the PCM isnt happy.

lucky131969

Perhaps....I would like to see the result of a jumper wire connected to the alt connector pin D, and alt. receptacle pin D........isolating the L&F terminal feed.

ianfelts

I will do that this evening, but which is pin D, farthest to drivers or passenger side?

So far as I know the alternator I replaced was the original, as the car only had 17K miles on it when I purchased it 2 years ago. I will get the part numbers from both when I get home from work.

byronhunter

ianfelts

With a jumper connected to the D pin on the connector, the current draw goes back to 1.7 amps.

Numbers on the original Valeo GM alternator are:
10246634
254192613
S45 AN 01

CoreyZ06

lucky likes to point out when i show my electrical ignorance. i dont fully understand how everything works.

BUT. when i am diagnosing a draw, i put my volt meter in series between the negative battery terminal and (-) battery cable, and start unplugging stuff until i find it.

good luck, hang in there.

lucky131969

Ok, to be clear. You have the main wire disconnected from the alternator, and the control circuit connector unpluged, with a jumper just between pin D of the plug and alt receptacle?

ianfelts

Yes, main power lead disconnected, still have all wires off of the B+ terminal as well, and ammeter inline on the negative terminal of the battery. Soon as I jump the D pin, it goes to 1.7 amps on the meter.

Any ideas? I am down to looking at the BCM or main computer as possible problems.

Bill Curlee

The BCM will NOT be the issue! The PCM may be. I will check my car tomorrow and see what the RESISTANCE reading on pin D of the alternator wiring connector that goes to the PCM should read. I will also see if there is any voltage on that pin when the ignition is OFF.

BC

Nick F

Just thought I'd try to lighten the mood a little bit. Good luck with this issue! I hate to see a Vette not on the road!

byronhunter

Just a refresher Bill, Pin D is the one that goes directly to Batt Voltage! He has the Pcm out of the circuit with the Connector disconected.

Bill Curlee

Went back and looked at my schematic and.......Pin D comes from the BATTERY and goes directly to the regulator. If your drawing current from the battery with JUST pin D connected,,,,Bud,,,your alternator is bad. Again, I will do some resistance readings tomorrow and see what pin D in the alternator reads to ground.

That will be a good point to start with. Read what your Pin D in the alternator reads to ground when the alternator is completely disconnected electrically.

BC

Bill Curlee

Just as I posted that post, I said CRAP! How the hell is the PCM getting power? Went back and looked at the schematic.

I think we posted at the same time or close to it!

lucky131969

I would like to see more isolation. Remove the positive cable from the battery, connect a 18 gauge jumper from pin D of the alternator receptacle and the positive battery post.

Bill Curlee

Pin D on the ALTERNATOR reads 145.5K ohms (145,500 ohms) to engine ground.

Pin D on the harness side has battery voltage 9as indicated by the schematic.

bC

ianfelts

Pin D reads 157,900 ohms, and battery voltage on the connector side.

With everything connected except the alternator controller, I see 1.94 amps draw across the pin D connector and the alternator.

I see this on BOTH original and new alternators. No variance whatsoever on any reading I have taken so far. I cannot believe that both alternators have gone bad in the exact same manner and to the exact same degree, down to the hundredth amp.

ianfelts

And test what, the draw across the negative battery terminal?

lucky131969

Yes, leave the ammeter in place, and just evaluate the current draw on the jumper to pin D of the alt receptacle.

ianfelts

Ok, I officially acknowledge that I am an electrical idiot. I need to RTFM for my test meter, and realize that I should switch the red lead to the other side port.

I am now going to rerun every test, after I finish beating my head on the desk.

byronhunter

Dont be using a soft desk Then get the battery load tested. When I read post #1, I thought "Bad Battery." Might not be it, Good Luck