2003 Sonoma Battery Drain,

The old battery was fried, but there is a battery drain issue. After turning off the ignition the radio will play forever. Then 30 seconds after turning off the key, the fuel gauge will actuate and read whatever level is in the tank and stay live. Any thoughts?

The obvious candidate would be the ignition switch – the thing that puts the car into various states (off-accessory-on-start) according to where you have turned the key. Ignition switches do fail and putting the car into the wrong state in whole or in part can be one of their failure modes.

Your sonoma has Retained Accessory Power. Which means if you have it in the on position and turn it to the off position you will still have power to things like the radio. If you open the door it will cut off the power. Does this sound like what’s going on? Does the radio stay on even if you open the door? What makes you think you have a battery drain issue?

The old battery was fried

If that was true, have you fixed the problem that fried the battery. A fried battery is not a battery fault, it is a charging system problem.

Yes The battery was replaced. 1 dead cell and would not hold a charge. The radio will not go off after the door is closed. Battery drain evidenced by sparks when hooking up the new battery. I would think ignition switch also, but it is strange that exactly 27 seconds as I count the fuel gauge starts registering again. My thought was the battery was fried after being constantly run down after the car was off. I’ll let ya know what the mechanics find.

Well the ignition switch was replaced, and battery drain continues. Wayne an ace mechanic was told by the gm dealer when getting parts that this was a recall issue for the instrument cluster in larger GMC vehicles, but not the smaller ones. Any clue would be appreciated.

Final word from the dealer, the gauges are supposed to do that. Previous repair of stuck door switch should cure the battery drain, Dash was removed and cluster checked, the mechanics called the factory and there are 2 gauges that are supposed to do the dance with minimal drain. If that is supposed to happen why did the dealer mechanics have to call the factory. Once again any clue appreciated.

I would be curious to know how much current is being drawn. Some draw is normal, say around 30 milliamps when things have gone into the sleep mode. You can’t use the sparking method to check things as some draw is normal and power needs to be on for a bit to allow the process circuits to shut down things not needed when the engine isn’t on. When power is first applied the current draw is much higher than the normal sleep mode current is. Normally when looking for this kind of trouble fuses are pulled one at a time while monitoring the current to help locate the trouble circuit.