I have a 2005 Suburban. About a month ago, I was sitting in it at lunch listening to CNN on the radio (on accessories, engine not running). After about 20 minutes, everything shut off and I had to get a jumpstart after work. The battery is about 2 years old. Got the jumpstart and headed home. I watched the alternator gauge the whole way, and it was charging fine. Got home, killed it, restarted it, everything was fine. I went out and checked it later that night, and it started fine. Everything was fine until today. Same story. Sitting in it at lunch listening to the radio without the engine running, and everything died. Got a jumpstart after work, drove home, got my tools, and headed to AutoZone to test the battery (started fine, again). AutoZone could find nothing wrong with the battery, so now I'm at a loss as to what's happening. Any ideas? The guy at AutoZone said he has NO IDEA what could be the problem.

 

Welcome to the forum.

Check and clean the battery terminals and tighten.

 

The radio is not the only accessory that is on when the key is in accessory. The problem might be one of the other ones partially running such as a motor for electric seats, etc.

 

Agree.

As an aside - I'm not 100% confident that those battery/charging testers are reliable. Your battery and/or alternator may be suspect.

Assuming they're not, then get a circuit tester and measure the current load when the truck is on accessory. I've never measured it myself, but I doubt it should be more than a few amps. If you have a larger draw, then start pulling fuses to see when the current draw goes down.

 

I second the thoughts of oldchevy twenty minutes with the accessory mode on, you are powering the radio, the On-Star system even if you don't pay for it or have it active and in some cases the air bag systems, the DVD drive if you have a DVD inserted and the CD drive if a disk is inserted...

you could be pulling upwards to 5-6 amps in accessory mode