So my A/C system is wierd everything works like the heat still colds hot the cold still gets cold, blower motor still turns on but not when i tell it to? I live in MN and its kind important this time of year to at least have defrost. Any ideas on what could be wrong? At the moment the system will randomly turn on only if i have the setting turned at 5 (highest setting available) and it will stay on for a few mins then turn back off. That only happens if im overly lucky. Depending on how fast im driving i can feel heat slowly coming out the vents so i know its working.

A friend said its most likely the computer system not telling it to turn on.

 

It sounds like your fan resistor has gone bad. What year is your S40? The 2000-2004 have a simple transistor mounted to a heat sink that mounts inside the ducts where air blows over the heat sink to cool it. Over time it simply wears out. The fix is very simple if you can solder a $3 Radio Shack transistor to the old heat sink. Otherwise you purchase the whole thing for $100 or so.

If this is a 2004.5+ model then *bump* cause that one I don't know.

 

So, does ANYONE know about the 2004.5+ models? I have been trying to find out where the resistor is on that generation but nobody seems to know. That's the whole reason I signed up on here and so far, no luck...

 

If no one else has had a problem with it then my guess is you have a different issue. When my 2005 gave me problems I replaced the whole CEM (the waterfall display in the center) with a junkyard unit. There are companies that can repair the CEM.