2002 Yukon XL electrical issue- when key is removed heater kicks on-drains battery

[joe4golf]

Has anyone ever hear of this? It happens when I turn off the engine and remove the key from the ignition- a few seconds later, the heater kicks on and the A/C light is on, but it's blowing hot air. Of course, when I took it in to the dealer, they couldn't get it to happen! I was just told by the dealer that there is a feature on the vehicle that it is supposed to kick the heater on to clear out any condensation or mold from the heating and air conditioning unit. It's only supposed to be on for 10 minutes and then shut off automatically. The problem with mine is that it stays on and drains the battery completely. Any feedback? Has it happened to you? Any insight would be greatly appreciated.