Alternator testing question

[jeromio]

If you recall from a previous post, I had some elec. trouble - starter would only click. I cleaned up the grounds and disconnected the alt and the problem was solved. I don't want to reconnect the alt if it's the source of my problem.

 

So, none of the local parts stores will test my alt - they say it's too new and they don't have an adapter for the test bench. (which is not true since I saw one in the drawer at autozone, but the guy said "it only had 3 of the 4 wires in it - I'm thinkin maybe that's all you need to test. Anyway...)

 

I got out the multimeter. Have no idea what I'm doing or what to look for. BUT, there is some continuity between the case (the body of the alternator) and the positive pole that runs to the battery pos post. That seems bad. Yes?

 

(BTW, this is a 99 Camaro V8 alternator).

[Guest Anonymous]

I hate to see an old post at zero replies!

 

As I understand it, the alternator has a full wave rectifier in it that converts AC to DC. This is accomplished by a certain arrangement of four diodes (which only pass current one way). This circuit is a direct part of the output of the alternator and you will get a resistance reading from the positive terminal to ground. You are reading the resistance of a part of the diode circuit is all. This is not to say that any one of the four diode is not blown and the thus thealternatori is not functioning properly.

 

I am no genius here by any means but you might consider connecting all the wires except the + and have someone sit in the car and run the engine up a little while you momentarily touch the + wire to the terminal. If you get a + reading on the dash gage then you are OK to go and mount the wire permanently. If it works, just keep an eye on it for a few days.

[jeromio]

I ended up taking the alt in to a parts store and having it tested. They said it was bad (shocker) and I ordered another one. Seems to be working fine now though.