Blue Burb

What say guys...first post to this forum.
Wife's 2001 Suburban 1500 4WD...Battery not Charging. Dash Voltmeter shows only 12 (battery voltage-no charge).
DVM confirms only actual battery voltage when running.
Took the battery and alternator into O'Reilly's last Thursday and both checked out ok. Battery less than 2 years old. Alternator is original.
I put new battery bolts on.
Cleaned the battery bolt holes;
Cleaned alternator connections;
Cleaned remote positive connector;
Confirmed continuity between all connections between alternator and battery;
Confirmed continuity between small positive cable going to the electrical center;

After I did all that, started up and I got 14 volts but it randomly fluctuated between 14 and 12 every now and then.
Son took it to work Friday and said it stayed up at 14.
Wife took it to work Saturday and said it just stays at 12.
That's where it is now.
We've been charging it but only driving to take the dogs to the dog park.

I've heard mention of ECM, BCM, PCM....???

Any advice is appreciated. Can't do with out the 'burb for the summer.

Thanks,
Steve

kevinkpk

Get a good battery

Blue Burb

The battery will charge on the battery charger here at home. DVM on the terminals when installed with engine running registers only actual battery charge level. No charge seems to be coming from the alternator.
Could it still be a bad battery ?

blueinterceptor

How's the belt?

Blue Burb

ahh, forgot to post that. belt is good too. no apparent slippage, no squealing, no cracks.

Does anyone know how I would check the signal going to control module of what the battery charge is? I've read that the control module turns the alternator off if battery voltage is within limits.

Blue Burb

ok, checked every ground I could find. all were clean. I check continuity on all of them with engine ground and got my tone.
I decided to check the brown and gray wires. Not sure what they're for.
I think the gray is the "field sense" and brown is to the "PCM" ?
Engine off, no voltage across either of them(to ground);
Engine on, not running: Battery voltage =11.6v; Gray = 0; Brown = 9.98v
Engine running: Batt voltage = 11.4v; Gray = 0; Brown = 9.96 volts;

Will take the battery and alternator out again when the boys get home and take for a retest.

But does the brn/gray test narrow possibilities down ?
Thanks guys

kevinkpk

Take your + lead to the alternator post on the back side, the other to frame or battery -. That will tell you if it is the alternator.

73shark

Did you check the alternator frame ground to vehicle ground?

Blue Burb

Yes. That looks good too.
Damn confusing problem.
Question: If I disconnect the PCM to make sure the connections are good, will I need to get it reprogrammed when I reconnect ?

kevinkpk

Did you actually put + side to the + stud on the back of the alternator, and - to frame with it running?