I recently replaced the thermostat on our 2005 S40 and solved a "check engine" problem. Recently however we have noticed that the heating system is not working at all. No matter what the temp dial is set to, it's blowing cool air. The dash gage shows the engine is getting warm but the cabin heating system is not picking up warm air at all. I've read in other places about a cabin air filter but the air velocity is not affected it's the temperature only.
One other point to note - the fans under the hood run a great deal once the car has shut off. I'm not sure if that is at all connected to this issue but thought I'd point it out since it seems to be a relatively new condition.
I don't believe it's the transistor pack and hope it's not the heater core. Any ideas how to troubleshoot and what may cause this chilly condition?
Thanks in advance.