72 Catalina heater control unit

[72catalina]

I'm having problems with my heater control unit where it wont switch the direction of the blower currently it blows down towards the feet and it will not switch to another direction is there a way to fix the issue or will it need to be replaced. I have not looked into the issue so any advice is welcome,thanks.

 

[melsg5]

check if any of the vacuum lines coming off the control unit are broken or disconnected on their way to the vacuum actuators for the blend doors

 

[72catalina]

How would i go about that considering i have little to no car experience

 

[melsg5]

If you intend to keep the car purchase a copy of the factory Chassis Service manual. Otherwise drop the lower AC ducting and check the hoses coming off the control.

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[cammerjeff]

I always start looking at the Vacuum Globe under the hood, I have found one of the 2 lines disconnected or the fitting broken off the globe several times.

They usually look something like this

http://www.ebay.com/itm/Vacuum-Reservoir-Dorman-47076-/181847553056

 

[72catalina]

Where would that be located sorry for the late reply

 

[cammerjeff]

I forgot to ask if your car has A/C? It may not have a Globe if it doesn't have A/C. Otherwise you need to check for Vacuum leaks under the hood and under the dash. That is usually what causes that problem, but it could also be a jammed air deflector door or Linkage, in addition to possibly a bad heater controller or switch.

I have not had that issue with my 71 so I am not really familure with the way the vacuum lines are roughted, and they may be different between years.

Does the car run and Idle OK? If so I would start looking for disconnected lines and or leaks under the dash, and at the heater Controls. Keep us posted please.

 

[cammerjeff]

A friend on another forum sent these pic's he said the Vacuum reservoir is the same on all 71-74 full size Pontiac's Located on the center firewall directly over the transmission tunnel. It is circled in yellow on the 1st Pic.
The second Pic is th3 72 A/C Vacuum diagram. He also had this to say for T/S

Verify the black is to full vacuum and the purple is going into the firewall (and holds vacuum).

Good Luck

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[cammerjeff]

And he just added these for the under dash coponates, the diagram is for 72-73 and the picture of the defrost Diaphragm is also 72-73

he also added this for the defrost diaphragm that is mounted near the passenger side foot well

The blue and yellow both control defrost, you need to verify that it holds vacuum and verify that when you put the lever on defrost that vacuum is coming to the blue for full defrost. If the diaphragm is bad, you can get it out without removing the heater box from the firewall (sucks, but doable) and replace it or repair it.

keep us posted on the progress

 

[72catalina]

yes it is an ac car it runs and idles really good thank you very much for your help ill check it out and keep you posted