Heater does not work on 1997 Oldsmobile LSS

Last year I had Sears replace a dead battery in my car. When I picked it up, the heater wouldn't work (just blew cod air). I argued with Sears and they told me it was not their problem. After several trips back one of their mechanics figured out what the problem was and fixed the heater. It has run fine until the other day when it was so cold out the car wouldn't start and the battery got drained. After jumping it I now have the same cold air problem. Does anyone know how to reset the system?

Asked by for the 1997 Oldsmobile LSS
Two things you could try. One is simple, the other requires a Tech 1 or Tech 2 scan tool (dealer). Try disconnecting the battery for about 1 minute. This resets the system. If this doesn't work, a scan with a tech 1 or 2 will reset the system as well as retrieving the fault codes. The fault codes are NOT retrievable with a "normal" scan tool! Of course this requires a trip to the GM dealer.