Question: 1981 Corvette Alternator Test Problem

[coffeejolts]

I was testing my alternator today using the matrix in the shop manual. I'm pretty sure the alternator is shot- I was getting 8v (battery voltage only) at the BAT post- seems like I should get 12-14v. However, I continued the test and checked the voltage at the the #1 connector. The matrix says it should be between 2 and 4 volts. Mine came back at battery voltage. Yikes!

My question is: should I be worried? Does this indicate something is wrong with the car's wiring harness? I apologize in advance for my ignorance.

 

[GerryLP]

Are you getting a "Gen" light? Is it at least glowing or off altogether?

It most likely means that the internal regulator is bad, but if you read on in the shop manual, you'll find that depending on whether you get a "Gen" light or not it can mean a few conditions.

Some of our membership are "Brainards" in repairing alternators. I just buy a lifetime warranty on mine, and if it ever breakdown, I'll take it to the nearest Autozone and exchange it.

Was the engine running when you checked it?

 

[coffeejolts]

The car was running when I checked the voltage. The battery light on the dash is on brightly and the dash volt meter is reading low (which is correct). I checked it once more after my post. The voltage on that connector is about 2 volts less than battery voltage, but way higher than the 2 to 4 volts described in the manual. Of course, that voltage may have changed as they worked through the different dash harness designs.

So far as I know, the alternator is original to the car. At the very least, it hasn't been changed since I purchased the car in 1997.

 

[LVMYVT76]

I would take the alternator off the car and take it to a shop that rebuilds your alternator, that way you have the original still with the car.They may be able to test it on the car so you will know if it is bad.

 

[bill81vette]

you should be able to get the internal parts for your alt at any parts house..eg auto zone,advance...
and they are not that hard to take apart...when you put it back together,seems to me I used a toothpick to keep the brushes out of the way till it was together then just pulled them out to reset them...

 

[Emtmike]

Alternator fix

I was getting the same problems with my alternator. I even had it re-built twice , and still it would make my volt gauge fluxuate. I replaced it with a 100 amp alternator, and havent had any problems with it, and the gauge stays where it's suppose to be .