Battery Drain - The Hunt Resumes

[khansen46]

I posted a while back about a parasitic battery drain on our 2000 Suburban. It's an LT 1500 4x4, which my wife inherited from her Mom. I put in an Optima Yellow Top, and didn't have an issue for a few weeks. Then the issue returned. I'm sure the battery just masked it for a while. Prior to that, we went through 3 batteries in about 5 years. Since then, I've kept a battery tender on it to keep it charged. We don't drive it much, so I haven't spent a lot of time troubleshooting.

Inspection time is coming up next month, so I've been driving it around lately. I noticed every so often the AC blower would slow down dramatically, all the lights dimmed, and the volt meter dropped to 9. It would last for only a second or two. I timed it while idling, and it happened about every 2 minutes 22 seconds. The RPMs never changed, so clearly it's electrical.

 

The alternator has tested good multiple times at the parts store, but since it's intermittent that doesn't mean much. I replaced the alternator with a new high output one (which is what it came with since it has pretty much all the accessories). I idled it in the driveway yesterday and the electrical only dropped once in 45 minutes. I was pretty optimistic for the first 19 minutes, but my heart sank when it did it again. 

 

I've gone through the exercise of pulling fuses, but no joy. I also replaced the AC blower motor a week ago. Apparently at some point while it was sitting for a while some mice built a pretty significant nest in the void above the blower, and the bearings were shot in the blower. Anyway, I know the blower motor isn't the culprit. The rear AC blower isn't currently working, but I doubt that is the issue since it shouldn't cause issues when the vehicle is off. However, knowing there have been mice in there opens up all kinds of potential causes. 

 

I'm not looking forward to the prospect of pulling the dash to inspect all the wiring, but I realize it may come to that. All the wiring in the engine compartment seems fine. I'll plan a day to let it run and see if I can find a definitive pattern to the electrical draw or interruption, and then start pulling fuses again. I've already removed power from the DVD player and power inverter, so those should be in the clear. If I still can't figure it out by that point, I may spend the money and replace the computer. I hate just throwing money at it, but it is very sentimental to my wife so I'll do whatever is necessary to get it fixed. 

[richard wysong]

any codes? the 2 minute thing could be a circuit breaker resetting or the thermal limiter on an electric motor. Does the a/c work? maybe a compressor issue if it doesn't .

Edited August 21, 2023 by richard wysong

[dna9656]

What all cycles on a rotational schedule? I know the A/C compressor cycles a lot on or off, I know it's part of the defrost thing, it dries the air so it defrosts more efficiently, that also contributes to keeping mold and mildew levels lower. I WOULD SUSPECT every motor you got, blower front and rear, wiper motor, windshield washer pump motor, bad grounds and shorts can make anything on the vehicle operate irrationally. Man I do not envy this trouble shooting safari!

[khansen46]

The AC was serviced recently, and works fine (except the rear blower, which I mentioned in my post). But I'll run the same test idling in the driveway with the AC (and everything else) turned off this weekend. I'll post the results.

[khansen46]

There are no codes present, and haven't been in quite some time. We had some sensors replaced a couple of years ago, but this issue predates that.

[richard wysong]

Did you check body codes or just powertrain?

[khansen46]

I used an ODB2 scanner and no codes are present. I've also had it at 2 different shops and they found nothing.

[swathdiver]

Tech-2 time Ken.  Or in your case you might want an MDI with GDS software so it will work on your 2016 as well.  

 

You use this tool to see which modules are still awake and how much power they are drawing.  I don't have a GMT800 anymore so I don't know which menu to check that or perform the parasitic draw test.

 

OBDII scan tool only queries the engine module, not the chassis or brake.