Let me say up front, diagnosing electrical problems is my weak suit so this may or may not be an easy one. I have a 2000 F-350 with dual alternators and my upper one was completely shot. I removed it and had it tested off the vehicle before buying a new one. Before anyone asks, I also have two brand new batteries thanks to the aforementioned alternator problem. So far, so good, right. Except that when I connected the alternator pigtail connector to the new alternator, I could immediately hear a faint humming sound coming from the alt. I disconnedted the connector and it quit. So I decided to check voltage on the pigtail. With key off, engine off, there is one hot wire, and one wire that reads 1.5 volts or so. I'm fairly certain there should be no voltage on that one wire when the key is off.

Other than that, everything else is working fine with the alternator system. I have run through all of the pinpoint tests found on All Data and everything is functioning normally except that I have a small drain which I think killed my last batteries and probably the alternator too.

I'm guessing this is probably an ignition switch problem but don't have any idea if that's true and if it is, how to go about isolating it to fix. Any help would be greatly appreciated. Otherwise I'll have to go to the stealership and no one wants that.

 

Bump for someone who's good at electrical diagnosis stuff.

Stewart

 

Anyone,...anyone? Bueller?

 

I have to admit I'm surprised my problem isn't interesting enough to get even one response.

 

If you suspect a small drain, you should be able to catch it at the fuse panel with a meter than can read DC amps. Find the offending fuse and then figure out what's on that circuit that could be the culprit.