1998 Olds 88 charging problem

Having an issue with the volts light coming on and the head and dash lights dimming. I have replaced the battery, alternator, positive and negative battery cables, and charging cable for the alternator. Car seems to run fine for the first 5 min. or so when cold and then the volts light comes on headlights start to flicker and blower motor slows while idling and while high revving in park. Everything is fine when driving until you lit of the gas and come to a stop and everything dims and volt light comes on and will stall I you don’t break and throttle at the same time. If you go to long sometime the ABS light will come on but clears after a restart. Not sure if it could be the Body Control Module or what else to look at. I have used the code reader for local parts store but it doesn’t throw and codes.

Ya need to recheck the battery state of charge,(at least 12.5v), with the engine off. Recheck the battery clamps,check for loose battery posts,check cables,connections,positive and ground termination points. Recheck the alternator connections and charging output,( around 14 point something volts),while running. Lights flickering could be bad diodes in an alternator or you might have a bad ground somewhere between the battery,engine frame or body. Substitute ground jumper wires between these points to try and narrow it down.

Get a voltmeter across that battery.....12.6 volts, cold, nothing on...

Start vehicle and should go 13-14 volts.....

Let it warm to normal operating temp.....should still be at least 13 volts....

Now load the system...headlights, blower on high, rear defogger on....may drop to between 12-12.6 volts......now raise rpms to 2K......voltage should increase above 13 volts.....if voltage remains low and battery is ok, need an alternator....

Timeline on when these parts were replaced?

Battery reads 12.5 cold
When started reads 15.2 form the alternator
didn't get a change yet to check reading after warmup yet.

Battery and Alternator were replaced January 2012. Had to replace
alternator in Apirl 2012(under warranty).

Started having this problem again when the weather turned cold and
started running defrost and blower on high.

Replaced replaced the power and gound wires.

Alternator is overcharging. Replace.

15.2v after a cold start is not too high unless it doesn't come down to the mid 14's.

After warm-up volts are 11.1 at idle and when revved to 2000rpm fluctuates between 11.5 to 13.1. Volts stay steady 14.3 if power break and revved to 1300 rpms. I have changed to alternator out four times(but not since running new power and grounds) so something else must be causing them to fail.

11.5 is no good the alt is not putting out or there is a high load on it. I assume the belt is tight. Have the alt bench checked.

There is an old saying....."garbage in, garbage out".....

There is a reason why some of these remans are so cheap.....

Anyone that has ever put an alternator, in a double overhead cam 3.4L Grand Prix, has found out the hard way, you put a good alternator in......takes 1.5-2.0 hours to put in, especially the first time.....and when that sucker doesn't charge right out of the box or fails a few days later, you will be cursing.....

There is an old saying....."garbage in, garbage out".....

There is a reason why some of these remans are so cheap.....

Anyone that has ever put an alternator, in a double overhead cam 3.4L Grand Prix, has found out the hard way, you put a good alternator in......takes 1.5-2.0 hours to put in, especially the first time.....and when that sucker doesn't charge right out of the box or fails a few days later, you will be cursing.....

Or a Ford Escape 3.0l !

Alternator bench tested fine. When ahead and changed the idler pulley since it looked rough. Has new belt and is tight. Started the car and let it idle for about a half an hour with defrost blower on high, headlights and radio all running. No light dimming and alternator was pushing out 14.4 volts. As soon as I put it in drive lights dim and blower motor slows down. And is only pushing out 11.2 volts.

If voltage is ok in Park, and isn't in drive, and then is ok when put back into park, then start moving wire harnesses to see if you can recreate the problem.....when you put it in drive, that engine will move and so will the harnesses, and flexing a bad connection in a harness could be your problem....

Also, if voltage drops in drive, does it increase if you increase rpm's with foot on brake?

After putting back in park, it voltage stays at about 11.2. Voltage increases with increased rpm's with foot on brake if it’s in drive, but when in park the voltage fluctuates between 11.2 to 12.1.

Have seen alternators bench test ok......but back in the car, when at normal operating temp, and with a load, they fail.....

Main wiring harness came unclipped on the drives side and was lying on the exhaust manifold. It melted and exposed the wires to the alternator causing them to ground out.