Rear climate control not heating 04

[excue2]

my 04 burb`s rear climate control is blowing a/c even when the temp control is set to heat. Front driver and pass are working fine. Just can`t get any heat out of the back controls. Any help would be appreciated by my 2 month and three year old. I am having to shut off the rear system and crank the front to warm them up.

[aztecf]

Same thing happened on our 05, dealer had to plug in there machine and reset something?

Jeff