Service Battery AND Low Coolant warnings

[Writefast]

2007 Yukon SLT 5.3. So after removing the MAF and cleaning MAF and throttle body I took her for a drive. Seemed a bit smoother than normal which was good. But about five min in the cluster threw the Service Battery Charging System Soon warning. I looked at the gauge at it was hovering just about 1/2 way between 9 and fourteen and dropping slowly. It’s blazing hot out so the ac was blasting and I was running full lights. Killed the lights and ac and gauge walked back up to 14 and then climbed a bit higher. Came to a stop in traffic so I decided to test. Turned in ac, no immediate change. Turned on lights and the gauge started dropping again. So I killed them all again. Traffic starts moving again so I test again. Ac, no problem. Lights, and the gauge drops but more slowly. Pull into a parking lot and open the hood. Nothing looks amiss. Coolant is full, all connections that I might have bumped or broken look good. I kill the motor (I have a portable jumper), wait five min and it fires up immediately no problem. Drive her back home and it’s pretty much the same except the coolant warning is gone. What in the actual FortNine is going on here? There’s no weird flickering as far as I can tell. Alt is only 2-3 years old. Battery less than a year.
There is one other weird thing. After reinstalling the MAF et al, when I fired her up I reached in and turned the key and released as normal, she did not fire up immediately but she did, without me keeping the key turned, continue to turn over by herself as I stood outside the vehicle. It was so weird it took a second to register. lol. Did that for maybe 10 seconds if that long and then fired up strong as normal.
I’m currently lost. lol. What did I break?

 

[Writefast]

One more thing. I let it sit and idle in the driveway after the drive with full lights and AC. Gauge stayed a hair above 14 and did not move.

 

[Writefast]

Fired her up again in the driveway. Ac, full lights, and fans kicked on at the same time and voltage drop. Turn lights and ac off and return to normal. No fans, ac and lights are tolerated. My meter says that charge is hovering between 13.3 and 14.8 when idling.

 

[tom3]

Serpentine belt been replaced recently? Maybe not turning the alternator fully when under big load. I'd get the alternator tested if any local place can do it. Can't rely on most replacement parts these days seems like.

 

[Writefast]

About 4 months ago on the belt. And having the alt tested is next. Just weird that this all started after fuckingbaround with the MAF and headlights.

 

[Fless]

Check that the serp belt tensioner is working correctly, too.

 

[j91z28d1]

with a good scanner you can read the current draw reading from the current meter. that would give you an idea if your headlights are pulling some kinda crazy current. these ecm's vary voltage all around it's not the most reliable gauge of load anymore.


I doubt the maf effects the alt, even tho anything seems possible.

alt is pretty cheap, you could take this as a good reason to upgrade to the newer style 220amp alt. you can find low mileage oem ones on ebay for 150$ ish last I looked. the part numbers and info is around this site somewhere. but basically a direct bolt on. that would at least rule out if the atl is failing.

 

[Writefast]

with a good scanner you can read the current draw reading from the current meter. that would give you an idea if your headlights are pulling some kinda crazy current. these ecm's vary voltage all around it's not the most reliable gauge of load anymore.


I doubt the maf effects the alt, even tho anything seems possible.

alt is pretty cheap, you could take this as a good reason to upgrade to the newer style 220amp alt. you can find low mileage oem ones on ebay for 150$ ish last I looked. the part numbers and info is around this site somewhere. but basically a direct bolt on. that would at least rule out if the atl is failing.

I’ll break mine out and see if it can read that. Didn’t think about using it. Thanks!

 

[Writefast]

NOPE. THIS WAS NOT THE SOLUTION. DISREGARD. DAMN THING IS STILL NOT CHARGING CORRECTLY.
AND THE SOLUTION WAS:
Bad alternator. More to the point a bad voltage regulator on the alternator. Now time to go break something else. lol.

 

[mikez71]

220 amp is only $160 for acdelco at rockauto. (use 2019-2021 silverado 1500 5.3) I was going to buy one to replace my used ebay unit because datalogs show my voltage continuously fluctuating .1V, but apparently that is normal with computer controlled alternators... a few bigger less frequent drops in voltage show up on my logs as well.