Very short duration "battery not charging"

[Paul Bell]

2003 5.3, 250K miles, one year old 200A alternator from Quick Start, three year old battery from Odyessy (NOT Optima). New battery cables last year. The engine cranks very well and starts without issue. Volt meter always at or above 14V.

Everything would be fine then with no warning, the tach would go to zero, engine power is gone, the battery light would come on and the DIC would display "battery not charging".

This only lasts a second then the display and light go away, the tach comes back and the engine continues along.

NO CODES.

This could go on for a while, every few minutes it happens. Then it won't happen for an hour.

Common sense and experience say if the battery or alternator were bad, it would be continuous, not intermittent for such a short period of time then not happen for many miles driven.

I have a 160A alternator on a shelf I'll sway in in the morning but I can't imagine that's it.

Any ideas?

 

[Mooseman]

Check your battery cables. Someone else had a similar issue with loose terminals.

It is possible for an alternator to intermittently stop charging. It will eventually completely fail. Happened to me.

 

[Paul Bell]

Yes, I'll do this. I was hoping this was heard of before.

 

[Tiggerr]

I definitely make sure all your grounds are good...as well as connection to the cluster...

 

[Paul Bell]

OK folks, I swapped back in the 160a alternator and checked all connections, positive and negative, all was good.

I have a 100 mile each way trip tomorrow, we'll see the results.

 

[Paul Bell]

The alternator swap fixed the problem, thanks guys. I'm glad but...

My old school understanding of alternators is that when they go bad, they simply stop putting out power-and the vehicle runs on battery power until it's dead.

About two years ago, I drove this truck to Detroit and along the way the alternator died-and it ran until the battery was dead.

How can a bad alternator cause the engine to just instantly die like that even when the battery is fully charged?

What do the two wires in the plug do? My LS1 Trans Am has a single wire in the same plug.

 

[Mooseman]

How can a bad alternator cause the engine to just instantly die like that even when the battery is fully charged?

It shouldn't happen unless there is a complete internal short that kills all the power?

What do the two wires in the plug do? My LS1 Trans Am has a single wire in the same plug.

IIRC, one is the 12v+ sensing wire and the other is the trigger wire from the PCM that tells the alternator to charge. I know the PCM does delay charging in very cold weather for some sort of self preservation reason.

Maybe the alternator gave a bad feedback through that wire to the PCM and would momentarily kill it? I've had the momentary "battery not charging" for a while prior to it completely dying but it never killed the engine.

 

[Paul Bell]

It shouldn't happen unless there is a complete internal short that kills all the power?

I'd think a short would show some cable damage. And when this happened, the radio and A/C fan kept going.

Maybe the alternator gave a bad feedback through that wire to the PCM and would momentarily kill it? I've had the momentary "battery not charging" for a while prior to it completely dying but it never killed the engine.

Perhaps. I'm gonna return the alternator to Quick Start to get to the bottom of this mystery.

 

[Paul Bell]

This annoying problem has started happening again-but this time, almost never with the "battery not charging" message on the DIS. The engine just stops running for a second then kicks in again. Sometimes, it just flat out dies and I have to re-start it, which it always does. Again, no codes.

I've had problems in the past with the oil pressure sensor grounding the 5V sensor circuit, which also feeds the throttle body and the MAF.

Although the OPS is the GM "professional" grade, it's acting up again, reading 80PSI all the time. This has been going on for about three months, about double the time the dying issue has been happening.

I wonder if they're related?

I'll be installing another OPS, this time, because it's so hard to get to, I'm gonna do the re-locate mod. Apparently, these sensors don't last.

 

[Mooseman]

What if you just unplug the sensor? You won't get readings but should confirm if it's responsible or not.

 

[Paul Bell]

HUH. Sometimes I need to dumb things down.

I'll try that, thanks!

 

[Paul Bell]

I THINK I have this resolved.

Unplugging the OPSU did not fix the problem.

After about six weeks of this going on without an SES light or codes, it started getting worse (happened more often) and I started getting codes for the crank sensor-still without illuminating the SES light.

After replacing the crank sensor, all appears to be good. But it's only been three days and I haven't taken any long trips. I'll report back.

Thanks everybody for the help.

 

[Mooseman]

You might need a CASE relearn if you get a code for a crank/cam angle.error.

 

[Paul Bell]

Yeah, I did that.