QuestionQUESTION: Hello!
My '98 Cirrus is a great vehicle, and it's in pretty good shape, but recently it's developed this heater problem:
In the morning when I start it, I get no heat, no matter how warmed up the engine is - that is, until I fiddle with the air temperature knob. Maybe a bit of tepid air before leaving - but the moment I start to move, freezing cold air. Then, I twist the temperature knob (it's a rotary knob) back and forth a few times, and, if I'm lucky, I get hot air with the knob turned to hot.
In the morning when I start it, I get no heat, no matter how warmed up the engine is - that is, until I fiddle with the air temperature knob. Maybe a bit of tepid air before leaving - but the moment I start to move, freezing cold air. Then, I twist the temperature knob (it's a rotary knob) back and forth a few times, and, if I'm lucky, I get hot air with the knob turned to hot. Once I've got hot air, sometimes I can adjust the temperature just fine, but sometimes touching the knob again, turning to anything but full heat, causes it to run cold again.
So I'm stumped - I mean, the temp control knob should just be mechanically moving a blending door, not turning the flow of coolant to the core on and off.
The radiator overflow tank is full, but not overfull. I see no coolant leaks. The engine warms up normally and does not overheat.
Now, coincidentally, the blower has more recently started working only on high - but I already know about the blower motor resistor thanks to a "Find" search and I'll be changing that when I open up the passenger-side under-dash panel to do whatever needs to be done to fix this no-heat problem.
Any suggestions of what I might check will be greatly appreciated.
Thanks
ANSWER: Hi Fred,
There are two doors that are operated by cables from the control panel: the blend door and the recirc door. If you look under the unit after removing the under dash panel you will see the two cables and the arms to which they are attached. The cable that is closer to the center of the unit is attached to the blend door. Check to see if it is moving the door lever arm. If it is slipping it could be at the arm or at the cable sheath itself on either end of the sheath. I can give you the instructions on removing the control panel to check for mechanical slippage at the knob end should that be your conclusion and also how to change out the cable if that is necessary. I think this is solvable, and you have a good start on it already. Let me know what you find and we can go from there quickly as I check for questions often.
Roland
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---------- FOLLOW-UP ----------
QUESTION: Roland,
Thanks for confirming that the blend door operates by a cable and not a motorized actuator. My Hanes is pretty vague on this area. I will check the cable action. Although I must admit that I'm unclear on how a loose cable would result in the heater going from working fine pulling into the driveway to stuck on cold sitting there overnight. Maybe it's spring-loaded? We'll see what I can see...
AnswerHi Fred,
You might also check after the engine is warm to see if the heater core hoses are about equally hot where they go through the firewall. Any significant temp discrepency would be grounds for backflushing the heater hose with a garden hose after removing attachements at the engine. Let me know how it goes. I don't see a spring involved in the door mechanism.
Roland
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