Battery Light Issue
 

Issue with my 02 Yukon-

So about a month ago, my Yukon's battery light came on while my wife was driving and slowly drained the battery until it left her sitting at our kids school. Luckily we only live a mile away so I jumped it (several times) and managed to get it home. Having owned this truck for 10 years and never replacing the alternator, I knew that must be the problem. So I replaced it along with the 4 year old battery in the vehicle.

Fast forward to this past Friday. Battery light comes on again and starts draining the battery. I took it to the parts store where I purchased the new alternator and battery and they say the alternator is bad. I put the new alternator in tonight. I let the battery charge for a while and start it up. The voltage on the dash is up above 14 but the battery light is still on, blinking every 3 seconds or so. So I disconnected the negative terminal again and rechecked all my work again. Are terminals every where are clean and secure. I even opened up the red box between the alternator and battery and cleaned all the contacts there. I also checked every wire and connection under the fuse box.

I don't own an ohm meter, but planned to buy one tomorrow. I know it's got to be be a wiring issue somewhere. Has anyone seen the alternator plug go bad or wires connected to it? When I google "02 Yukon Alternator Plug" there's a bunch or results, so I assume they must go bad on occasion. Am I missing something? I've searched forums high and low and it seems all the answers are different. I'm just hoping it's not the computer...

Thanks for any help!

Get your meter and measure the voltage across the battery terminals. When the truck is running, the alternator should be putting about 14.5 volts across the battery. Watch this voltage and see if it varies when the battery light comes on. Depending on what you see here will determine what the next step will be. Good luck with it and let us know what you find.

It measured 14.6 pretty consistently. Didn't fluctuate much even with accessories on. Dropped to around 14 at lowest.

All the tests looked good. Plug too. Think the alternator could be charging correctly but maybe the internal regulator is no good?

It would seem the internal regulator would be what controls the output of the alternator. If it is putting 14.5v across the battery, it should keep it charged unless the battery is bad. Since you have replaced the alternator and the battery plus checked fuses and wiring there's not much else that I could suggest. Grounds? I hope one of the Chevy techs will chime in and help out. Please let us know what you find. Good luck.

So I went back and got another alternator. This time a brand new one (only $50 more which I was never offered previously). Put it in and I battery light. Fingers crossed this is the fix. I spoke to a technician at our local Chevy dealer and he said these model years are finicky to refurbished alternators. Lesson learned...

You can't argue with success but it does seem strange that the replacement alternators had the same problem as the original. Glad it's working and hope it continues. Thanks for letting us know how it went. Good luck.