A few months ago I realized that while my car's temperature was fine, it was annoyingly not always coming up to temperature inside the cabin. (Some mornings it would heat up just fine, and other mornings it would blow cool.) I called my pet store, and they told me they were too busy (perhaps they don't like me?) and suggested someone else for me to contact. I got in touch with the other folks, brought the car in... they spent several minutes not-detecting a problem, and were about to turn me loose when one of the kids there said "hey -- look -- this piece (the connection to the controller which is mounted just on the other side of the firewall) is broken". The boss didn't think that would cause my problem (if it hadn't broken in the "open" position I'd never get warm) but they took my car info and told me they'd order the parts from the dealer, call me, and get it fixed. On the way home, while sitting at a light it started blowing cold again. I was about to turn around and go back to the shop, but as soon as the light changed and I started moving it got warm. *light-bulb* (It was the mornings that I was stuck in stop and go traffic when it most annoyingly didn't warm up.) I called back with this information, and he suggested that a flush was in order. December was busy, so when they didn't call back, I let it go.
However, in January, along with the other 5 appointments I was trying to set up, I called them. The admitted they'd dropped the ball, and picked it up again. Tuesday I had one of my appointments, Wednesday another, and today I took my car to the radiator shop. (The weekend before I'd driven for an hour in -5 degree temperature, and that was quite miserable. Hopefully the magic will cause the temperature to go up to 50 at least and stay there for the next few months.) They did what they needed to do, charged me for an hour (I'm guessing) of labor -- which was about the same price as the part -- and now I have heat. For at least the last few months, if I turned the fan on above the 2nd notch (of 4) it would blow cool. I drove back to work with it on FULL HOT -- and blasting out of every vent I could get. Happy happy! Roasty toasty!
The mechanic who delivered the car to me said that he had flushed it, but only a little came out, and that I might have some problem with "some veins in the water pump" because when the RPMs go down, it starts blowing cool. Ok, I'll remember that. But meanwhile, driving back to work today, even stopped at traffic lights, it was still blowing warm.