I have a 2001 Volvo S40 1.9 T and heater only blows cool air. No matter what temperature is put on control it still only blows cool air. I have put on auto fan and upper vents and temperature of 78 and it still blows cool. A/C works fine and it blows cold. This has been intermittent as sometimes the heat worked but lately only cool air.
I checked the coolant level and it was above MIN and I added a little to it but it still is under MAX.
No warning lights or anything of that nature.
Is there any test that can be done to isolate the cause of this problem.
Any help is appreciated as winter is approaching and freezing is happening overnight.

 

problem is likely with the air blend door not actuating so the airflow through the heater core is not getting to the vents. Could be a motor or actuator rod. Any warning codes like blinking AC/REC lights etc?

 

I get no warning codes whatsoever. Today when I used the car absolutely nothing was done to any settings on the three dials. It was on 2 for fan, upper vents on direction, and temp was on 78 and it blew warm air like it was supposed to do.

It seems as if the temp setting **** is where the problem may be. What is this connected to, some sort of sensor and if so where is it located and can I test the device in some fashion.

Since it is working I have no desire to change the settings as heat is the desire this time of year but would like to resolve issue.

All help is very appreciated.

 

next steps would be to see if you can get a scan for any fault codes from the HVAC computer (dealer may need to do this) which would indicate if there's a faulty sensor or motor, then open up the sides of the center console to take a look at the actuator controlling the blend door - see if the rod is detached or if the door is stuck.

 

Might work. I haven't tried it. manually resetting damper motor.

http://www.matthewsvolvosite.com/for...hp?f=8&t=34858