Cadillac Repair Questions? Ask a Mechanic for Answers ASAP
do you have a dual zone temp control?
if you have dual zone you will want to make sure with the fans off you can here the flapper doors moving when you change the temp control. it is hard to hear so you need a quite spot. if you hear the doors moving or you do not have dual zone you have a plugged heater core. sediment will settle and plug one half od the core and you will only get heat to one side.