Hello everyone,
I am hoping to get a little help or advise on a problem I am having. When my car is on and running the battery, break and open door warning lights come on. I pulled the Alt out of the car and it tested just fine when out of the care; however, it did not pass the test when it was in the car. When the Alt was in the car it came back low volt according to the guys at the auto parts store. I checked out he battery leads and the positive has some corrosion but does not look to bad. Based on what the tests came back with I am guessing that the problem is in the wiring some place or a relay box of some sort. I could use all the help I can get..

Thanks so much everyone, normally I would post in the introduction section first but really need to get my ride going so I can get to work tomorrow afternoon.

 

Start with the simple stuff. Disconnect the battery and clean all ends of both battery cables. You want to make sure they are making good contact.

If you have a volt meter, you can check the voltage across the battery terminals with the engine running.

Copy and paste this link in your browser. This is an excellent video on initial diagnosis.

youtube.com/watch?v=FTGz0PKIl84

 

Also check the other wiring harness to the alternator - the small wires not the big power wire.

The wiring harness to the alternator contains a control wire that signals the alternator to shut off. If that wire is pinched & shorting to ground, that tells the alternator to shut off. I'll have to look around to find which wire that is, color code, etc...