Battery went dead on my 2004 trailblazer. After that the a/c will only work on defrost and at your feet. No air will blow out of the front vents when in correct mode. Anyone have any ideas as to a reset on it or something. THe dealer was trying to tell me I needed a $550.00 vent door or something. I somehow felt maybe that wasn't true and the battery failing had something to do with it. Thanks

 

There is a possibility that the module has gone into what GM refers to as "logic lock". Basically it has frozen and won't issue the command for the mode valve to operate. Try this......disconnect the negative battery cable and then the possitive battery cable. Then hold both of them together for about 30 seconds, make sure they are getting good contact with each other the entire 30 seconds. This will discharge any capacitors that are holding a charge. Then reconnect the battery and start the engine. Let it run for an entire minute without touching anything! then see if the mode door will respond to commands. If it doesn't you're not out anything, but if it does..you may have saved 550.00! repost and let me know, and we'll figure it out if it still doesn't work.