I have a 2003 Cadillac STS. A/C works fine however, heat blows cold, both sides. Using a simple temperature test I have verified coolant appears to be flowing through heater core
, not 100% certain but trouble isn’t leading me that way. I have checked all the actuators I could find, 2 on driver side and one on pass side of console. One is bad however it is located lower rear left/drivers side and appears to function for rear controls and only affects the rear when changed manually.
I even pulled the cabin filter and while it was nasty and corroded, I believe sufficient air should have passed though. Anyways I testing without the filter, just reattached the cover so air would not leak out the cabin filter access port. Same no heat.
The only symptom other that when I call for heat bower comes on, blows cold. I can change from vent floor and other setting w/o problem. On occasion, if car is warm, I turn heat on vent mode I feel warm air (not hot) for a few seconds then it blows cold, same as outside temp.
I am at a loss and could use some guidance. I am now thing of taking apart the entire duct work assembly under the dash. I rather not since access it and the various screws holding its various parts will suck.
Anyone who believes the know what’s wrong chime in, I will pay for info that leads me to a solution.