When ever i turn my car off i can pop my hood and put my ear to the alt. and i hear a whining/humming noise. If i dont unplug the connnection at the top of my alt. at night, when i get up in the morning my battery will be dead as a hell. If i do unplug it in the mornings when i try and crank it, it clicks every time, about 5-10 times before it cranks. If i hook jumper cables up to another car it starts right up, no problem what so ever.

Now when i first crank it up in the morning when its cold the alt. has a good strong charge at about 13.8-14.4v. After about 10 minutes the alt. gets real hot and the volts. vary from 12-14.0v. Plus when im turn my lights, heater, or fan (manual fan) on the volts drop real low, then fluctuate at about 10-14 volts. I had my alt. checked (its 1year old) and its fine. My battery is 2 months old and my connections are new. The thing that has me baffeled is that the connection i disconnnect at the top of the alt. (91' TA LB9)
is the 12v wire and neg. that control the fans. Alot more info is availible if you have any questions or might now whats wrong.

 

The 2 top wires on the alt are ignition 12 volts for the field, and the sense wire which is also ignition controlled. Regargless of the test it sounds like the alt has an internal problem. Unless the wiring has been modified and the field line is staying hot all the time, which actually should not cause what you describe because it usually destroys the regulator IC sounds like it's a bad alt. Basically everything in the charging system is internal to the alt.

 

What you are saying about the two top wires makes more sense to me considering that my "Haynes" manual wiring diagram shows them running ONLY to the fans. I dont know why. But the car has been screwed with bad and im slowley but surely getting it back to normal. There is a wire coming from the alternator "i suppose, its goes in the the Black wire protector that runs to the alternator" but the wire is run to my fuse panel and one day i accidentally kicked it and my car wouldnt charge but the alternator was good. A few days later i found the problem and put the wire back in the fuse panel and my car started charging again. What does that sound like?

Whats the field wire and the regualtor IC?

 

The alternator consists of 2 sets of windings one is a stator (the field coil) the other is the rotor (Voltage output) Since an alt doesn't use magnets it has to get a magnetic field from somewhere...the field coil provides it.

Regulator IC is a voltage regulator made from an Integrated Circuit.

 

 

The reason the manual shows the sense wire going to the fan is because it uses the voltage at the fuse panel to feed it, the alt plug wires have nothing to do with the actual operation of the fans. BOTH of the wires at the alt plug MUST be operated by the ignition switch. If the alt makes noise with the car off, just unplug the plug from the alt. If the noise goes away measure to see if any voltage is on either of the wires with the ign off. Perhaps the wire you hooked up is on a circuit that is always hot. I have never tried powering up either wire on the top of the alt individually although I have rebuilt quite a few of the CS 130's. It is not recommended to do that. There is a problem with the newer "D" versions called "false biasing", meaning if you attempt to install one without the battery disconnected and both the plug and the rear wires are installed with power on the regulator IC can fail. If you unplug the plug and you still get noise chances are the alt is in fact bad. The rear lug is always hot, it is fed thru a fuse link directly to the battery. Make sure that wire that came off is on a switched ign feed.

 

I unplug the top to wires on the alt. every night to keep my battery from going dead. When i unplug them the noise does go away. But if i let my car sit for a day with the alt. unplugged the battery eventually goes dead. Im gonna get a voltage meter tomarrow, but tonight im gonna try and disconnect the wire going to the fuse panel from the alt. and see if it has the same juice tomarrow when i go to get in it.


Just awhile ago when i unplugged the wire going to the fuse box instead of the top 2 wires the humming when away also. Im gonna see if thats makes any difference than unplugging the top to wires.

 

91GTABIRD,

Did you find the cause of this? It sounds exactly like the issue I am having only I have a manual fan switch and when the switch is turned to the on position with the ignition off the humming noise stopps.

Any help is appreciated.

 

Nope. I just ended up having to switch one of the wires.

 

Did you notice any difference in the charging performance of the alternator?