I purchased a 2008 Subaru Legacy Outback about a month ago. Everything in it worked great during the test drive, including the AC. It's middle of summer where I'm at, so checking the heat didn't even cross my mind; all of the fluids were good and I took it on an "extended" test drive to make sure it wouldn't overheat or anything.
Just the other day, I got to noticing that when the AC was turned on, it had only one setting; cold. Turning the temperature knob (blue dot on the left for cold, red dot on the right for hot. aka not "climate control") so I thought to check the heat to see how hot it got, but there was no heat. When you turn the AC button off and rotate the temperature knob to red (hot) there is no heat; it just feels like regular air blowing through the vents. I've switched vents from defrost to feet heat and everything in between and there's absolutely no heat coming through.
I'm fairly mechanical inclined..I'm no mechanic, but have always done a fair job at doing self-repairs as long as I have the tools for the job. So, I got to diagnosing the problem. Again, I checked the coolant levels and they were fine. So I felt the hoses going into the firewall and both were hot..Just to be safe, I disconnected the hoses and flushed the heater core.
Which leads me to believe that there is something going on within the dash. I'm not very comfortable disassembling the dash and it's components without a diagram showing me how to do it and how to put it back together.. but I did what I was comfortable with. I took off the plastic interior pieces that surround vent knobs and radio which aloud me to (kind of) see behind the temperature knob. There is a wire w/blue rubber housing (think: like a hand brake on a bicycle) attached to the temp. knob and that wire runs up into the dash on the driver's side of where the radio slides into place. It is attached to one side of a white-ish lever thing and when I turn the temp. knob, it pulls and pushes the wire to manipulate that white-ish lever..but it looks like that lever should also be attached to something that it isn't..but I can't tell because it's too far up in the dash. Maybe the white lever shouldn't be attached to anything else..but that's what it looks like from my awful view..
In order to explore this further, I would really need a diagram explaining what I'm looking at or at the least how to get to it and put everything back together once I'm done.
To recap; I have checked the coolant levels and flushed the heater core. neither showed any signs of malfunction or damage. There is absolutely no heat coming through the vents when I turn the heat on, it just blows regular air. The knob does have tension on it and the wire is moving when I turn the knob back and forth. the wire is attached to something up in the dash and that "something" is moving when I manipulate the temp knob..I can't see that white lever good enough to tell if it's movement is doing anything or attached to anything else.
If anyone has any ideas on what may be wrong or where to find the documents that I'm looking for; please comment and let me know.