Robby1870 Posted June 30, 2003 Report Share Posted June 30, 2003 Okay, so I know the alternator and battery are good. Now, the cars starts fine, but after driving it some, the voltage on the battery drops to around 12 volts, the car doesnt die or anything, it just gets low. Then, if I hit the A/C and turn it on for a few minutes then turn it off, the voltage on the battery goes to 13+. Its like the voltage regulator in the alternator is sorta messing up, and if I kick the A/C on, it remembers to tell the alternaor to charge the battery. Anyone have a clue?? Robby Quote Link to comment Share on other sites More sharing options...
Brian P Posted June 30, 2003 Report Share Posted June 30, 2003 Take a wire brush to the battery terminals and wires then torque to spec Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted June 30, 2003 Report Share Posted June 30, 2003 Well, the only thing I can think of is that your alternator is really, really bad at LOW RPMs. Do you do a lot of stop and go driving? Are you idling a lot? Because the only thing the ECM does when you turn on the A/C is command a HIGHER idle RPM, this results in the IAC(Idle Air Control) valve moving a higher number of "counts" or "steps". And of course, as you hopefully already know, more RPMs equal MORE alternator amperage/out-put. Most cars drop slightly in voltage when the A/C is on because of the higher electrical LOAD, but for whatever strange reason, yours is doing the exact opposite??!! I always like watching how my ECM reacts to various loads put on the engine, I watch it via my AutoXray OBD scanner. Usually the A/C results in about 200 more RPMs. Besides this, I don't really know what else to say. Have you checked the voltage at the alternator and THEN at the battery to see if there's any voltage drop? I still think if you're NEVER getting anywhere near 14.5 volts, you're definately NOT getting a proper amount of amperage to the battery, it's being under-charged, whether this is because of wiring, or the alternator itself, including the regulator(which in internal), is hard to say from here... Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted June 30, 2003 Author Report Share Posted June 30, 2003 the battery connections are all clean and tight. Yeah, I measued the voltage at the alternator, and the drop wasnt that bad. I cant remember the actual numbers, but it wasnt bad. I do do a lot of stop and go driving, basically right now, two and from work. And, I havent had it above 3K rpms in a few days. The reason I ask, is because I am going to Indy on Monday, and dont want something to crap out. Yeah, I Know the regulator is inside the alternator. The A/C thing just blew my mind. That makes no sense to me. Im going to guess that whatever tells the alternator to charge the battery is going a bad?? And, Im assuming this is in the alternator. I Had the alternator tested at Advance and it was good. Another question, my dad's truck has a battery charge fuse or something like that, which, if it goes bad, makes the line that the alternator uses to charge the battery not work. I dont think my car has anything like that, but I was just curious. I honestly have no idea. I think the voltage regulator in the alternator is going bad, and that wont show up on a test at Advance. So, there is a alternator rebuilder here near town, so when I get back, I think I might have him rebuild it Robby Quote Link to comment Share on other sites More sharing options...
Bolt_Crank Posted June 30, 2003 Report Share Posted June 30, 2003 alternators are easy to rebuild, just buy the kit, and unless you have to rewind the coil, you should be good to go. and the voltage regulator is a little plastic box inside the alternator.... I used to know how to test it, but I forget, anyway, you can either get it from a junkyard, or, if you can find it, from a dealership or parts place, don't know the price though... Quote Link to comment Share on other sites More sharing options...
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