Complete HVAC failure
06-10-2016, 09:47 PM
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Join Date: Nov 2009
Location: Calgary, Alberta, Canada
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Complete HVAC failure
Hello guys
I'm attempting to diagnose my complete lack of HVAC control. I believe that my Temperature Control Unit (TCU) is dead but need to be sure before I commit to buying a new one. $$$
I have absolutely no control of output temperature, recirc, defrost, or the upper and lower baffle controls. The only thing that does work is the fan speed switch. The AC has been dead for years, but I'll worry about that later (not a necessity in Canada).
Of course I've done my best searching this forum. I've checked the flap control linkages and replaced the white clips years ago. I checked the operation of the coolant valve behind the engine (it is normally open and closes with vacuum applied). I've checked that the various vacuum actuated flaps work when vacuum is applied but I cannot sense any voltage at the solenoids.
I pulled out the cabin interior temp sensor and it shows about 12K Ohm at room temp and decreases when heat is applied. However, I tried applying 12V across the other two leads on the sensor but the little blower motor would not spin.
I do not know how to get access to the mixing chamber temp sensor.
Where can I find a diagram for the pin connectors on the back of the TCU so I can check supply voltage and/or circuit continuity?
Any thoughts on other diagnostics I can run to rule out other issues?
Any and all help is always appreciated!
Thanks.
I'm attempting to diagnose my complete lack of HVAC control. I believe that my Temperature Control Unit (TCU) is dead but need to be sure before I commit to buying a new one. $$$
I have absolutely no control of output temperature, recirc, defrost, or the upper and lower baffle controls. The only thing that does work is the fan speed switch. The AC has been dead for years, but I'll worry about that later (not a necessity in Canada).
Of course I've done my best searching this forum. I've checked the flap control linkages and replaced the white clips years ago. I checked the operation of the coolant valve behind the engine (it is normally open and closes with vacuum applied). I've checked that the various vacuum actuated flaps work when vacuum is applied but I cannot sense any voltage at the solenoids.
I pulled out the cabin interior temp sensor and it shows about 12K Ohm at room temp and decreases when heat is applied. However, I tried applying 12V across the other two leads on the sensor but the little blower motor would not spin.
I do not know how to get access to the mixing chamber temp sensor.
Where can I find a diagram for the pin connectors on the back of the TCU so I can check supply voltage and/or circuit continuity?
Any thoughts on other diagnostics I can run to rule out other issues?
Any and all help is always appreciated!
Thanks.
