Testing Alternator in the car.

OK....after my COMPLETE engine rebuild....I'm finding some little gremlins which is to be expected. One of which is that I suspect my alternator is not functioning. Lights are dim, car actually died at one point, and just now I disconnected the negative battery cable while the motor was running and it imediately died. Voltage at the battery while the car is running is 12.75 volts. A curious note however, is that the "G" light has never illuminated. I never had any electrical problems before the rebuild....but then again all these peices have sat for the last several years while I've been doing this rebuild. So my question is this......is there a way to check to see if the alternator is producing output while it is in the car? I would imagine I could put a DVM on the starter side of the conection....however I'd imagine I'd burn my hand pretty quickly with the headers being right there. I checked to make sure I reconnected the ground strap by the rear motor mount, and that is connected. Any ideas?

 

easiest place to check wih a DVM would be the ciggy lighter or in the fuse box.

With the engine not running, and no voltage drop in the wiring :
12.7 volts is 100% charged
12.4 volts 75%
12.2 volts 50%
12 volts 25%
<12 volts is dead

with the engine running and the alternator charging it should be 13-14.4 volts ?

 

any other suggestions?

 

Most repair shops have a load tester that tests both the battery and charging system.

There's probably one very near your home.

Take the car in and have them check it.