Ok have a 83 Toronado and have a intermittant problem with the charging system, the amp guage will be fine and all of a sudden its discharging. I have no headlights on or heater or anything substantial that would make it drop down to under 9-10 volts and then has quick has it dropped its back up working again? I have checked the battery even swapped it out with another and still a problem. Any suggestions? I suspect a intermittant alternator but did do a test on it as well and it checked out, still may be intermittant I guess?? I have checked the battery connections and all good. Is there any other wiring say to the dash or fuse box or anywhere else that could cause this problem??
One other thought was was the wiring that goes from the firewall and bolts together to the fuse box ???

 

So do you have an ammeter or a voltmeter? In any case, either the regulator is bad or there is an intermittent in the harness someplace. One option is to temporarily connect a voltmeter directly to the threaded post on the back of the alternator and watch what it does when the factory gauge drops. If the second gauge also drops, it's the regulator. If not, it's the wiring. Finding an intermittent wiring problem, however, can be a nightmare.

 

Actually, as I think about this more, if the battery is fully charged, even with the alternator not turning you'll read more than 12V, so I doubt the problem is the alternator or regulator. This is almost certainly a problem with wiring or the gauge itself.

 

I agree with Joe. If the volts are really dropping that much suddenly, I would not suspect the alt, but rather a large short or drain on the battery. If the gage is bad it may show that, but the volts will not be at the voltage you specified. I would first look at all positive wires of high amperage capability, like the alternator battery wire or the battery cable to the starter to make sure it is not rubbing and touching somewhere on occasion.

 

Sorry I said it was the amp meter but in fact it is the volt meter. I am thinking now that maybe it is like you guys said that it could be a wire shorting out somewhere. I did do a voltage test before at the battery wire going to the alternator and it was the same has the battery voltage. The regulator on the 83 is in the alternator is that not correct? I could possibly disconnect the main battery wire off the alternator and drive it that way for a bit and see if it still has the drop on the voltage guage? That could be one way to determine if the alternator is good or not????

 

Yes internal regulator. How often does this volt drop happen? I would first do a visiual inspection of the wires to see if there is anywhere the wires may be rubbing or laying on something hot that would cause wires to wear thru or melt. If you disconnect the alt battery wire or unplug the regulator from the altermator, the battery will go down if you run the car long enough. You can try it your way, but I don't think it will reveal much. Are there any electrical components on the car that do not work? Have you added anything electrical like fans or stereo?

 

I did do a a quick check of the wires but will do a more thorough check. I did change out the stereo, the one in the car was malfunctioning. It is a aftermarket stereo but does seems to be working ok?? Is it possible I'm hooked up to the wrong power or ground which may be causing some problems?

 

You may have to attempt to isolate the problem through process of elimination. It appears that you have eliminated any possible battery problem by trying another battery and assuring clean contacts. If your accessory voltmeter shows the voltage dip in agreement with the car's voltmeter, then the gauge is probably not the problem. Since the battery is "good" a drop in voltage "to under 9-10 volts" would probably indicate that the alternator/regulator is not at fault unless it has an internal intermittent short. You can isolate it from the rest of the car's circuit to determine this. If the alternator/regulator prove good, then there is an intermittent short somewhere else in the vehicle. Since no fuse blows, either it is not on a fused circuit or it's duration is so short that the fuse will not blow. You can eliminate a circuit from consideration by removing its fuse. As has been said, electrical problems have the potential to cause frustration. Proceed logically to minimize the agony.