gatrus

After changing 2 alternators and 2 batteries the car does the same thing. It starts on the battery and it dies when I unplug the battery. When I put the tester with the battery running it says 12 volts and not the 13.8 as it should.There is power going to the alternator on the big wire(held with a nut),
but no power on the 2 plugs. I'm not even sure if there is power there or not. Can someone give me a clue where to look.

RickMN

First off, you should NEVER disconnect a battery with the car running. That's a great way to fry all the electronics in your car--computer, radio, etc. Secondly, there should always be battery voltage on the large red wire at the back of the alternator. That's a direct line to the battery. It's basically the output.

The input is on the connectors. One is field voltage, another sense voltage. But since you didn't tell us what year and engine you have, it's hard to tell you which is which.

You're throwing parts at the problem instead of doing diagnostics. So stop hating the car and read up on how the system works.

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I'm a retired ASE Master/L-1 Technician. I still keep current with the latest automotive technology. Visit my blog for cool articles and TSB's: http://www.ricksfreeautorepairadvice.com/

gatrus

Problem solved. There was no current going to my 3 wire plug. It must be cut somewhere or corroded. I ran a wire from the battery to the plug and now its charging close to 14.