What are signs of a alternator going bad. Im still having wierd occurances with my car not charging up after I turn it off. Its wierd.

 

With the car running, put a voltmeter across the battery. What does it read? A proper reading should be around 13.5-14.4 volts.

Since you have a serpentine setup, it will proably take you longer to drive to your local auto parts store to test it out, then it will to actually remove the alternator from the car. Takes me about 15 mins.

 

The "true sign of a bad alternator"? Constantly having to jump-start your car.

Typically, a car won't charge after you turn it off. Not weird at all.

Anyway, I'm just being less than useful because Omar pretty much said it. 13.5-14.4 volts with car running. Anything less=bad sign.

 

If you meant that you are losing a charge when you leave it sit, the proper way to track that down is through probing your harness and fuse panel until you isolate the offending circuit.

 

some parts stores will do an on car check for free. we did this at murray's discount auto when i worked there, the diagnostic tool would check the battery, starter and alternator and it was really accurate with diagnosis.

 

haha mine is dying and it sounds like a supercharger, so that is one sign.

 

Thanks guys!!! Im hoping that its just heat soak but I will find out this week.

 

I always use the voltmeter too... engine off = 12 volts, engine running = what Omar said.

Also- something odd on my '86 Firebird- it has a battery light. Know how all the dash lights come on when you turn your key to "on" before you crank the engine? Well, if this dumb battery light is NOT ON, it means the alternator's regulator has fried. Stupid, eh? Who looks for a MISSING warning light? Argh.

A common failure for my year of alternator (mid 80's) is rear bearing failure due to overheating. One alternator that died was throwing sparks! "What's that noise? I'll pop the hood- oh s%#*!!!"

 

with the engine running....disconect the battery......a good alternator will keep the motor running....if it's bad it will die as soon as you pull the connection.

 

does it matter - or +???

 

DO NOT DISCONNECT THE BATTERY!!!!!!!!

this is no longer an acceptable method of diagnosis, it can screw stuff up bad. i can't remember the specific details but i know you're not supposed to do that

 

Hold a screwdriver on the back and see if it is magnetized

 

my freind has such a good charging system in his 84 camaro that you turn off the car and the radio will keep going for about 45 seconds...