If I leave my truck set for over a week it will not start. I just checked both batteries and have 11.7 volts on each. Load checked both of them and they both show weak. Last time this happened I charged both batteries and they load tested fine. Could I have a drain? If I have the batteries replaced under warranty (expiring in December) are they going to prorate them or will they replace both if they test bad.
Thanks, John

Take it in and have them replace both batteries under warranty. Depending on the dealer, they might even try to diagnose the problem. They should replace both batteries for free since you're within the 3/36 warranty. And you have to replace both batteries at the same time in a dual setup like that - no way around it.

Dealers will only replace what req replacement based on there determination of what is causing the issue, there is no statement saying that both batteries have to be replaced at the same time in any gm information.

Dealers will only replace what req replacement based on there determination of what is causing the issue, there is no statement saying that both batteries have to be replaced at the same time in any gm information.

Okay, well he might be taking the truck in for a warranty engine compartment fire if they don't - but he said that both batteries showed 11.7V and both failed the load test...

If it wasn't an electronic (ie capacitance type) tester used, then have them tested right. A regular carbon pile tester is inadequate to accurately determine the condition of a battery, especially a partially charged one.

Finally took the truck into the dealer. They replaced both batteries under warranty. Hope this solves my problem. Don't know if they checked for a drain problem but time will tell.
John