I have a 1997 Explorer 4x4 4.0L. The alternator is recharging the battery. When I try to run the head lights, Heater, Foglights and the Radio at an idle the idle goes down and the voltage needle goes down. While moving no problem. I was thinking it was probably the voltage regulator. I have replaced the IAC. Does anyone have any ideas or had the same problem. Thanks

 

More likely to be the alternator is getting weaker, or it has always done this. The alterator has a certain rated output in amps (I don't know what yours is, it could range from 60 to over 100). That rating is at a specified RPM (for the alternator not the engine). At a lower RPM, the alternator will not produce as many amps (like at idle speeds), however, that does not mean it will produce greater than rated amps at a higher RPM, it's more like making a threshold value. Have you used a digital voltage meter to check the voltage under the idle conditions you described? If the voltage is over 13 volts, the system is still charging the battery (even under the large load you described), and you should probably not have any concern. If the voltage is close to 12 volts, the system has lowered itself to the battery voltage and has exceeded the alternators charging capacity under those conditions. You could increase the alternator RPM if you could find a pully that would fit it with a smaller diameter where the belt rides, or you could replace the alterator. It does not sound like the regualator has any problem from your description, but as it's internal to the alternator, it would be replaced with the alternator. Another thing to check is to make sure that all of the connections to the battery are tight and clean (including the connections at the solenoid for the +wire and the frame/engine ground for the -wire). Loose and/or dirty connections can be the cause of voltage fluctuations.

Good luck, but in all probability you don't have a serious issue at this time.

 

have the battery checked , i noticed mine doing this especially when the rear defrost was on , the battery checked out bad and the problem was fixed .
hope its somthing simple and cheep.
john

 

My 92 xEB had the same problem right before the starter solenoid went bad. The voltage meter fluctuated from 14-16v. Lights surged. It drove me crazy. It finally wouldn't start, esecially warm. When I replaced the starter assembly, it ran like a champ. Also, it was hard starting or hardstarting before I replaced the assembly.
My suggestion to anyone with these kinds of problems take the starter off and have it bench tested. You can bench test it yourself with some jumper cables and a battery.
When tested, my starter spun, but had no KICK. Actually the bendix was bad. It seems that when the starter or solenoid is bad, it causes many electrical problems even battery drain.

Hope this helps

Mike
1992x EB & 89 BroncoII

 

um, that's a big load on a stock 65 amp alternator / 65 amp battery. Let me guess, you hit the gas and the needle jumps back up and the dash lights come back on full bright? Most stock alternators don't produce full amperage required to support the load of the truck (which is why all emergency vehicles that are diesels have load managers / PTO / engine idlers) at an idling RPM. If your alternator / battery check out ok, it's par for the course. You're sucking a LOT of power out of a battery that doesn't have that deep a reserve, and the poor alternator isn't spinning fast enough to supplement it!

It's the same reason that idling a car for long periods of time kills the battery!! YOu sit there at a sub-par RPM for a long time, the engine is sucking power out for the computer, spark coils / engine electronics, etc...and the alternator is putting out less power than the car needs, so when you shut off the car after a while...and try to start it up, it lugs or doesnt' start at all! Granted, the car was "running"...but all it was doing was running it self dead! Some people might think that just increasing the alternator output would help it, but not many alternators produce full voltage / decent amps at 600 - 750 RPM...If you're hell bent on running thta big a load for extended periods of time, increase the alternator output size AND the battery capacity...or install a load manager. :-)

[realizes expost facto that he repeated a lot of what JerrySimm said] :-)