1978 Thunderbird Auto Temp Control Issue?

[Canon_Man]

My Dad's '78 Diamond Jubilee has had some work done on the AC (new compressor specifically).

The AC works, but it doesn't seem to blow cold air out of any of the vents. I'm thinking maybe it's a snesor, or actuator that is not getting a good vacuum signal, or the heat plenum door(s) are stuck.

Has anyone experienced an issue like this, and if so are there any common issues that would cause it to act up?

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[stevo]

Hi. Did you ever find the answer

 

[Canon_Man]

No, no one has come forward.

I may have some things to check, like making sure the heater / evaporator box is clear of any 'critters' since the car has been in storage for some time.

 

[7T9_Tbird]

I have a similar problem on My '79 Town Landau. We've replaced the controls and checked and rechecked the vacuum lines and servos. Did you ever find the answer?

 

[Canon_Man]

I have a similar problem on My '79 Town Landau. We've replaced the controls and checked and rechecked the vacuum lines and servos. Did you ever find the answer?

Haven't had time to check it out further, but I think I may have an idea about why it stopped working.

It ices up which tells me it is either low on refrigerant, or the evaporator is blocked. Since I've already tried to top it up in October 2015 to no avail, I think what might have happened is that mice may have made a home in the heater box, effectively blocking the flow of air. Means taking the heater apart to inspect. No time right now.

Reason I suspect rodents is that around the same time as the AC stopped working for my Dad, there were mice that got into the cabin and ripped the center fold-down arm-rest and driver's seat apart. Small hole in the wheel house in the trunk area.

This odd peice of body damage was repaired, and the seat was rebuilt and recovered. But, I'm thinking my Dad never stopped to wonder where the critters took the material they scavenged.

Detective work to follow one day ...

 

[Canon_Man]

Found the 'cause' of the ATC not working ...

A sticking 'Throttle Valve' in the suction line returning from the Evaporator.

The valve can stick due to sitting, but can also be caused when the valve becomes defective. Apparently, Ford, GM and Chrysler used this valve back in the late 60's and early 70's and it isn't necessarily unique to the T-bird.

There is no affordable replacement OEM part, but there is a low cost solution manufactured to replace the valve and restore the AC to full operation.

Fortunately I didn't have to go that route. 🙂