How do I test my alternator?
 

I'm not sure if my alternator is charging my battery when truck is running. I'm not driving the truck yet just able to get it started and sit there idling. I have a multimeter tester. Is there some way to hook up my meter to tell if the alternator is actually charging when the truck is running?

how to
 

With the truck off, check the voltage at the battery. Then start the truck and check the voltage at the alternator. You should have a slightly higher reading at the running alternator. Take your alternator reading from the larger terminal on the backside which has the heavy guage wire attached to it. Your alternator voltage should also rise with an increase in rpm's. good luck

When you say to check at the alternator terminal, do you mean the one that has the one single red wire attached to it? Is it supposed to be thicker than the other two in that clip into the alternator itself? I did the changeover to internally regulated alt and made all three wires the same thickness. Blue and White into the clip and red bolted onto back of alt.

with the truck running your battery should read 14 volts or so.. anything about 13.5 would be good.

I always just cranked the engine, then pulled the ground wire off the battery. If it dies, the alternator is toast, if it runs, your good to go. Of course I'm just a shade tree parts swapper!:D

krue's method will tell you if the charging system is working, by pulling the positive cable with the motor running if the charging system is not supplying voltage the motor will die, if it does not you are getting a charge from the altenator, if it dies then either the wiring, voltage regulator or altenator is bad, when you have the positive wire off and if it stays running then turn on the headlights on bright, if it continues to run you know charging system is strong and puts out enough to supply recharging the battery during heavy electrical draw.
GMCPaul

Most Part stores have a tester too. If ya want you could go that way for the alt.

When I worked as a repair tech, we alway's did what krue, and GMCpaul said. The testers stayed on the peg. Since you went to the integral alt, that eliminates testing the volt reg independently. Now, is the alt not charging since you made the conversion?? Maybe the wiring setup isn't quite right yet?

I can't drive my truck yet on the road. I've only been able to start it in the driveway. I've been doing a lot wire gremlin chasing and was turning the lights on more often than I should of I guess. I think that is what drained the battery. Haven't been running it long enough to check the battery.

Just pulling a cable off the bat will only let you knw a little bit. Your engine only needs a few volts and a couple amps to run. But the battery needs more than that to charge up and also running all the stuff like headlamps.
Take your multi-meter, and hook it to the batery. Set the tester to Volts DC and to the lowest scale that is over 15 most likely that will be the 100 volt setting.
Start the engine and rev it up a bit to kick in the one wire alt and make it start charging.
Look at your meter, anything over 13.4 or so is good.
Anything less than 12.5 and your not charging at all.
Anywhere inbetween those two readings means you are charging...but not enough.