hafamaZing

my 2000 mustang's voltage regulator in the alternator failed about a month ago, and i replaced the alternator and the battery just to be sure. and ever since then the battery light has remained off and on whenever it pleases. i generally notice it come on once the car is up to tempterature. the lights dim out and the windows are slow to role down etc, when the light is on but when it is off everything is really bright and quick to react. i checked all fuses, and the connections all look nice and snug, what could be the problem?

01MGGT

Have u tested the voltage yet? Was it a rebuilt alternator? I have had bad ones before. Is your idle speed low?

hafamaZing

i got the alternator from autozone. they ran their testing machine, it says the diodes and regulator are fine. i havent had much time to use a multimeter on it or anything. i just need to figure out what the problem is fast, im supposed to be selling the car. i can run it in the morning cold til it gets up to temp, and then that light comes on. thats what confuses me. and i ran a wire directly from the alt to the battery, bypassing the one that goes through the fuse panel and it still comes on. could it be the belt tenstioner? its been squeeky lately, but i havent noticed any problems with it?

01MGGT

replace your belt. Sounds like once the belt is getting warm maybe it is slipping? Also check the idler pulley next to the alternator. Usually the belt will cause a problem before the tensioner will go bad. Also are you sure the idle speed is good? Because idle drops once the motor gets warmed up and can cause the alternator not to spin fast enough.

hafamaZing

at a stop light it probably idles about 750. i dont notice it dropping really low. both idler pullys are new as well, the bearing went out on one so i just got both of them and replaced them. the belt is fairly new, but i can go grab a new one and see if that fixes it. they dont cost too much. should i check the iac? i cleaned it out as well as the plenum about 6 months ago.

ChalknCover

If you do the belt, get a gatorback, there is none better IMHO. I don't think the IAC would have an effect on it, generally that causes a weird idle, vs just a lower one. Was it a reman alternator or was it new? I have gotten plenty bad ones from AZ before, we stopped using them for alternators for that reason.

hafamaZing

i think i just came to the conclusion the spring in the belt tensioner is bad. so i bought a new one. the belt is close to brand new. i will install the tensioner tonight and let you guys know whats going on. i think it was a reman alt. but there is alot of slack in the belt and the tensioner doesnt hardly keep any pressure on the belt