First time posting. This car was wrecked and sat for 5 years. I rebuilt the front end, and put a new long block in it. Runs great...BUT, it wont charge. Alternator and battery both tested good at AZ and AAP. AAP report states a "diode short" causing a 119mV ripple which is apparently killing my battery. Ive tested the A/C diode and its good. The only other diode is the one in the alternator and it tested good. What is killing my battery? All wires in the charging system have been tested, by me, and are good. Any help would be much appreciated. Thanks

 

What voltage across the battery posts when the car is running? It should be high-12's to upper-13's, DC. I don't know if a tenth of a volt AC ripple is out of spec...maybe it's acceptable under full load.

 

If you have just battery voltage at the bat while the car is running, check the "charging" post AT the alternator.

PS-personally I'd like to see 14v at the battery when the car is running

 

12+v with engine off and 14s with engine running. So the car runs fine if you jump it, but doesn't start up once you turn it off or what? If so, you to do a parasitic draw test to find out what is draining your battery.

 

Thanks to all that posted replies. Over the weekend I replaced the alternator, power steering pump(it was leaking onto the alt), and starter. While I was doing that I used my charger to charge the battery. The car ran great Saturday and Sunday, but when my girlfriend took the car to work this morning, the ABS light came on, indicating low charging voltage, which is really pissing me off. The charging indicator doesnt come on, only the ABS light. Maybe the light burned out, who knows. As far as testing voltage at the alternator and battery, 12.5 with car off, high 13's when running. That seems right to me. When the car is off, there is a .03A draw, which I dont see draining a good battery. Looks like its off to Jerry's Auto Electric to see if they can pinpoint the trouble. Thanks y'all. I appreciate it and will keep you posted.

 

13V while running...something isn't right. 14v maybe, I like 14.5.

Waht is the voltage right AT the alt charge post?