Alternator draining the battery?
 

A week ago, I topped off the coolant in my '66 (due to a leak that I've since fixed). I apparently didn't put the radiator cap back on tight enough, and some coolant sprayed all over the engine compartment while driving. I cleaned up the mess as best as I could, but the next day my battery was dead.

I had the battery tested, and it had a bad cell, so it was replaced. I also replaced the voltage regulator and battery cables for good measure (they were in rough shape anyway). The truck started right up, and I drove it around that day.

The next morning - dead battery again. Looks like I have a short somewhere.

Using a multimeter, I figured out where the battery drain is coming from - the alternator...at least I think. It's a standard three-wire alternator, and if I unplug the little plug (with 2 wires), the battery drain disappears.

Now, here's the question...does that mean the alternator is bad? It's no more than 6 moths old, so I don't want to replace it if I don't have to. But, could the spray of coolant have cause some sort of internal short or something, or should I be looking elsewhere?

Re: Alternator draining the battery?
 

try plugging those wires back in and unplugging the voltage regulator to see if the drain stops. coolant should not have damaged the alt. unless there was some thing wrong allready. you may have gotten a bad regulator?? try that if it doesn't work post back and i will look at a schematic and see what goes where :uhmk:

Re: Alternator draining the battery?
 

I know that a bad diode in an alternator can cause a drain on the battery.
The little wire in the pigtail which is usually white and smaller than the other wire should only be hot when your key is on. The other wire which is usually red, and is larger should be hot all the time. Does that help?