novaks47

I suspect the voltage regulator in my alternator is toast, or nearly toast. Or maybe one of the diodes is toast. Last week the voltage on the onboard meter was fluctuating every now and then, swinging between 13V-15.1V. Also when the voltage swing would happen, the dash would dim back and forth. With all the rain I haven't had much of a chance to test much, but today I got my battery tester on it, which has an alternator check function. It showed the charge voltage at 14.77 volts, and ripple as "high", reading .51 volts. This was done at the battery posts mind you. Started raining so I had to stop my diagnosis. What's the ok range for ripple on these cars? Does it look like the alt is a goner?

Hot Rod Roy

This sounds to me like a bad ground or bad connection, rather than a bad regulator or alternator. You wouldn't have 14.77 v. output if you had a bad diode, and 0.51 v. ripple voltage sounds reasonable, although I don't have valid results to back up my opinion. Here's the test results of mine, but the ripple voltage was not reported:

84 4+3

When I rebuilt mine it idled around 13.5 with a mild load. 14.7 sounds reasonable with nothing on at the battery.

I don't know very much about ripple but I would imagine if you had a diode problem it would be very much worse. The easiest way to check for it as far as I know is to use an led test light and see if it flickers. It doesn't take very much for them to if there is a ripple problem if I remember correctly.

novaks47

Thanks, this is precisely why I figured I'd ask before throwing money at it. Once the rain stops I can start checking the grounds.