alternator only charges when it wants to!

[cheepyclipse]

This sounds like a regulator problem to me, but i just thought i should run it by somebody else to see if there is something i missed. Last night while cruising my head unit turned off on me and i noticed my lights were dim, and i thought O CHIT, my alternator isn't charging! so i headed to my shop and when i got there my battery was definatly dead as the car wouldn't restart. so first i checked all my cables for corrosion and found them clean. I wanted to check to alternator so i put the car on the charger and started it. when idling it had some where around 11.5 volts and steadily dropping, so the alt wasn't working. I checked all the fuses and relays and everything looked intact, so i was like damn i guess i need a new alt. I left the car running a little while and did a wiggle check on all the wiring on the alt and the harness leading to the main underhood fuse box...nothing. I was just about to give up, i was smoking a cigarette and thinking about how much i didn't want to buy a new alternator, and then rwwwwwwwwwwrrrrrr, the alternator obviously kicks in out of nowhere and the voltage is 13.5 or more, so i load it down with the ac headlights stereo amp windshield wipers and its still putting out 12.5, i was like oh well i guess i fixed it, but i know i'll have to find it tommorrow. well its tommorrow now and it still only charges when it wants to, i replaced the battery and checked the fusible links for continuity every thing checks out, every once in a while it will charge good and then sometimes it wont. help me wisemen!

 

[cheepyclipse]

oh yeah, i only have a crappy haynes schematic for this car. where does the pcm come into the equation? under what parameter does it send what signal to the regulator, all i see is a box with "PCM" in the schematic and the wires leading from it dont correspond to the ones i see in the car. also, i have noticed that the alt relay has little or no function in my car, under what conditions does it toggle on? it must sense amperage to work since it only has two connections right?

 

[BigAirSkier1580]

My car did the EXACT same thing. The altenator was shot. Replaced it and the car ran perfectly.

 

[luv2rallye]

The brushes in the alt have worn down. Get them replaced in a alt/starter repair place or get a new/rebuilt alt.