Alternator: How to check if its Bad?

[mountie1982]

Can anyone tell me how to see if the Alternator is no good in my blazer. I am having problems starting it. I changed the battery cause it was old and it was having trouble starting. i still having the same problem. I read some posts and I have some of the same problems others are having. The fix seemed to be the alternator. When i go to start it all power is lost. When I pop the hood or beat the crap out of the steering wheel the power sometimes comes on. Then soemtimes I got to jump it. I had a post going about this and I figured I fixed it by cleaning the the cables and checking all the contacts. So i starting to lose it. So before I do I am gonna try to test the alternator. So if anyone can tell me how to check it that would be nice and save me from blowing the blazer up.

[2000blazerls]

Try licking it!


No seriously, Autozone can check it for you for free. Or any repair shop with a good battery charger. My battery charger, when hooked up can tell you if the starter/battery/alternator is good/bad.

[BlazerLT]

Check the battery voltage when the engine is running and see if you are getting 14.4+ volts out it for starters.

[OverBoardProject]

Turn your headlights on after dark, but before you start it.
Start it, and if the lights get brighter it's working

[Rmbodie]

Use a real voltmeter , NOT the one in the dash . Check the voltage on the battery when engine is off. Then crank it , Check the voltage while the engine is running , the voltage should be between 13.5 and 14.5 volts . DO NOT try disconnecting the battery while the engine is running to see if the alternator is working . While the engine is off , check the wire and harness on the back of the alternator for corrosion . It will cause a voltage drop and keep the battery from charging correctly . Rob