[deerslayer1985]

I have an 08 acadia. I drove to town and ate at a restaurant. Left there to come home, but had to stop and get gas. Stopped pumped gas. Started back up and about halfway home service charging system popped up on the dash. The volts were still showing what Id estimate to be 14 on the gauge. I was about 15 miles from home so I just drove on home. I immediately got my multimeter. Battery shows 12.68 volts. I fired the car up and the volts go up to 13.8 volts and hovered between 13.8 and 14.2 volts. So the battery is showing good and the alternator is showing its charging. I even hooked up my obd reader and looked at live data and it showed 14.0-14.2 volts when running. The service charging system light is still on, but all voltages should be good. It fires right up no hesitation. I went ahead and stuck a battery charger on the battery just to top it off and see if it changed anything, but is there anything else that could cause that light to come on? Thanks for any help.

 

[rbarrios]

repeat the test with vehicle running---
but then turn on
rear defroster.
headlights to full on, and high beams.
blower motor on high
radio
and if you want-- step on the brake pedal to light up the brake lamps
and clean your windshield with spray-- so the wipers wipe.

See what the alternator does when all this load is added.

 

[deerslayer1985]

Ok I'll try that shortly. I did drive it again late last night though and the service charging system and battery light went off.

 

[deerslayer1985]

Well after a turning all things on in the car and checking it was still charging. So I was confused. I thought maybe a weird coincidence. After a couple more times driving I get the light again and see the voltmeter dip below 13. I head home immediately to test. Get home service charging system warning is gone and testing good. I continue to drive it daily. This happened a couple more times. Finally I decide the alternator must be starting to go bad. So I pick 1 up, and im getting ready for the removal. I go to disconnect the red powercable to the alternator and it wiggles really easily. Im like oh crap. So a quick tighten of the nut on the stud and I think my problems r solved. Shoulda checked there first. Lol

 

[JayTee2019]

Well after a turning all things on in the car and checking it was still charging. So I was confused. I thought maybe a weird coincidence. After a couple more times driving I get the light again and see the voltmeter dip below 13. I head home immediately to test. Get home service charging system warning is gone and testing good. I continue to drive it daily. This happened a couple more times. Finally I decide the alternator must be starting to go bad. So I pick 1 up, and im getting ready for the removal. I go to disconnect the red powercable to the alternator and it wiggles really easily. Im like oh crap. So a quick tighten of the nut on the stud and I think my problems r solved. Shoulda checked there first. Lol

Well. . . it's at least always good to find something obviously a cause sooner or later. Right !

 

[deerslayer1985]

Yea. Glad I went to unhook the wire first before jacking the car up, taking off wheel, inner fender well, and taking off the belt, and taking the idler bolt out and all that. Id have been a lil more upset...lol