QuestionI have a 2000 Blazer. My heater is stuck on no matter where the temp gauge or if I have the AC button on. The local auto parts store told me it is the heater control valve. However, I have had several other people tell me it is probably the Blend Door Actuator. When I turn the Ac on, the AC compressor kicks on, just no cool air. Could it be the temp control button? Depending on what it is, what do you think the suggested repair method is? Fix it myself, take it to dealer....etc???
AnswerBryce,
The most logical direction is the Blend Door and/or Actuator. The Actuator controls the door, but I've seen the heater case itself break at the door hinge, causing the door to fall inside. If you can make it to the Actuator (make sure it's the Blend, since some systems have more than one, particularly if it's automatic), it's possible to remove them without pulling the heater case, and then manipulate the door with your hands. If you can do that, and the temp changes -- breathe a sigh of relief, because the heater box shouldn't have to come out.
The problem is, that doesn't tell you if the Actuator is the fault. The control head (where the temp control is) supplies the proper signal to the Actuator, so you'd have to test that. It's easy with a scantool (like the Tech2) -- you just command the actuator through the Tech2, and if it works, then chances are you have a Control Head issue. If not, then the Actuator is most likely the cause. Since they are electro-mechanical parts, actuators are the most prevalent culprit. However, A/C Control Heads have been known to fail as well.
Due to the increasingly complex nature of A/C systems (they have diagnostic codes just like engine management systems), I would suggest a professional look at it. Although there are many good independent mechanics out there, I'd also suggest taking it to the dealer, since they are equipped with scantools (most aftermarket scantools can't drive blend doors), and have most likely seen this issue before. Good luck!
