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I've been dealing with this for about a year now, I'm fed up and out of ideas.
Currently, the alternator only excites if I disconnect and reconnect the connector a certain way. Like i have to tug on the harness while connecting it.
Now for the background and what I've done...
I had no issues for about a year after I bought the car. It started as an overvoltage issue that I traced down to the fusible link at the started for pin D. I gave it a little tug and it pulled right out of the terminal. Replaced it, no more "high voltage" readings when I hit bumps. But that was the start of the not exciting issue.
I've hit the terminals with a multimeter, big red wire reads battery voltage, pin d reads battery voltage. I don't exactly remember the L and F terminal outputs, and I don't know what they are supposed to be. One read 10 something volts and the other was millivolts if I remember right.
Anyways, I thought it was something wrong with the D wire since that's where the issue started so I ran a direct battery to alternator with a fusible link with no luck. Same issue.
I've checked and double checked the lug on the starter. The big wire has a little corrosion on the terminal, but not enough to where it would cause any problems I think. I've replaced the alternator twice, so that's out of the picture. I replaced the pigtail connector with no luck either.
I'm at my wits end with this, just wanted some advice before I finally call it quits and take it to a dealership. I just know it'll be difficult explaining all this to them if I do.
From your description of the problem, the alternator does charge so the excitation of the field seems to be working or you would never get output from the alternator. The tugging sounds like a connector pin/socket isn't making a solid connection, have you inspected all of the sockets for damage and insuring they engage the pins and make a good mechanical connection. Past that I would look for an intermittent in the harness, it's a long shot but twisting the harness may uncover a break in the wiring.
I don't think it's the connector since it did the same thing before and after I replaced it. And I'm on my third alternator so it shouldn't be that either. I've inspected the wiring up to the injector connectors, I guess the next step is to start looking up there. I'm just worried that the overvoltage did something to the L terminal in the pcm.
St. Jude Donor '14-'15-'16-'17-'18-'19-'20-'21-'22-'23
Originally Posted by CorvetteKeithf
Warrantied by O'Reilleys.
I'm gonna say that is your problem. Many GM alternators will fit and plug in, but they are missing a circuit inside of them. Evil-Twin did a great write-up on this
3 Oriely alternators. 2 bad (pulley wobble and other threw charge error) and 1 was good as it did not throw the charge error. I know each orielys is different as they order from different vendor locally.
Mine I tested with a volt meter and clean voltage across the board.
Ask Bill Curlee or Evil Twin (a different Bill) as suggested above.
I asked BC about my 04 because the bearings are starting to make noise and he said it does have the special circuitry in it that many posts reference. I have read many posts about alternators from Advance, Auto Zone, O'Reilleys that don't excite properly but unfortunately the GM alternator has been turned in. There is one thread where the OP went through three then just bought an OE alternator and it was fixed. Bill told me to have my alternator rebuilt at a professional shop rather than turn it in to a chain store and hope they got it right.
I trust them completely.
Last edited by Ed Ramberger; Mar 28, 2018 at 05:42 PM.
I tried this and 5 shops around me that rebuild alternators all quoted a standard build cost. I asked if they used valeo parts for a vette in the alternator and they all looked at me like I asked them to build the Eiffel tower. They all stated they use standard parts (what ever they have).
I even told them I could bring in the valeo voltage regulator for the rebuild and all stated they wouldn't allow that. Sending it out of state to fix was to costly and hate that for warranty purposes.
...I asked him about my 04 because the bearings are starting to make noise... ...Bill told me to have my alternator rebuilt at a professional shop rather than turn it in to a chain store and hope they got it right...
If you are going to take the rebuilt route, 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.
GCG has got the good answer. Try the right regulator.
There is no special circuit inside the alternator. The regulator just works at different voltage levels compared to the rebuilds. The Corvette PCM only provides 10V at a limited current on the L wire so the regulator has to be able to work with that signal since it's the signal that excites the alternator.
If you have one of those test lights with a probe, try connecting it between power and the L terminal at the alternator before starting it. You may need a helper to start the car while you hold the light backprobed into the connector. You could also just try revving it after starting and see if the alternator kicks in once a higher rpm is reached. If both tests are successful then that indicate its the regulator.
Last edited by lionelhutz; Mar 28, 2018 at 08:33 PM.
GCG has got the good answer. Try the right regulator.
There is no special circuit inside the alternator. The regulator just works at different voltage levels compared to the rebuilds. The Corvette PCM only provides 10V at a limited current on the L wire so the regulator has to be able to work with that signal since it's the signal that excites the alternator.
If you have one of those test lights with a probe, try connecting it between power and the L terminal at the alternator before starting it. You may need a helper to start the car while you hold the light backprobed into the connector. You could also just try revving it after starting and see if the alternator kicks in once a higher rpm is reached. If both tests are successful then that indicate its the regulator.
what is the f terminal supposed to read, the L terminal does read the 10 volts at startup
'04 Alternator Not Charging
