72 heater/defroster function
Thread Starter
Melting Slicks
Joined: May 1999
Posts: 2,897
Likes: 0
From: Moon Township PA
72 heater/defroster function
The car in question is a 72 without a/c. I just repaired my clock and after re-assembling my center cluster and console, I may have run into a bit of problem. The "air/def" thumbwheel on the left of the control unit blows anytime the fan is on. The owner's manual states "When this control is in the "OFF" position, the system is totally inoperative." In addition, there is not a noticable difference between defrost and air when I rotate the thumbwheel. I believe that the thumbwheel controls the air/def function by vacuum with the round mulit-connector on the side of the control unit. How does this also shut off the air (if it does this function at all) when the fan switch is on? Can anyone shed light on a good place to start looking? This car passed its ops check twice during Flight judging so I know it worked. I also know that I had half the dash and cluster apart so it can be anywhere. I just don't know where to start looking for either a connector loose, the vacuum connector loose, or anywhere else.
Any ideas, guys and gals?
Gary
Any ideas, guys and gals?
Gary
Melting Slicks
Joined: Sep 2001
Posts: 2,218
Likes: 0
From: Glendale AZ
Re: 72 heater/defroster function (GaryS)
that area of the center consold is a tight place to work in. When you rotate the wheel from Air to defrost it moves a small vacume assembly. The vacume assembly is the one with 5 or 6 rubber hoses to it. Take off the asembly and expose the cluster of rubber hoses.
Grab your trusty hand held vaccume pump and try it on each hose.
The vaccume should reach anywhewre from 10 to 20 psi.
When you "suck" on each hose you should hear movement in the dash. That movement is the diaphrams opening/closing doors for the system.
One of the hoses (Ithink its green) is the source. It comes from the intake manafold.
If any of the hoses does not hold vaccume (except for the source) then there is a leak, and you Should file a flight plan, create a sortie, and seek n' destroy the leek.
good luck
chad
Grab your trusty hand held vaccume pump and try it on each hose.
The vaccume should reach anywhewre from 10 to 20 psi.
When you "suck" on each hose you should hear movement in the dash. That movement is the diaphrams opening/closing doors for the system.
One of the hoses (Ithink its green) is the source. It comes from the intake manafold.
If any of the hoses does not hold vaccume (except for the source) then there is a leak, and you Should file a flight plan, create a sortie, and seek n' destroy the leek.
good luck
chad
Thread Starter
Melting Slicks
Joined: May 1999
Posts: 2,897
Likes: 0
From: Moon Township PA
Re: 72 heater/defroster function (71'AirStrike)
Chad, how well do think vacuum controlled devices work when my engine is not tunning? :mad Like an idiot (a tired one though) I was testing things with the engine off (hasn't been run in quite a while) and the ignition on. No wonder it didn't work. :smash: It works just fine, thank you, with the engine running.
Gary
Gary
Safety Car
Joined: Apr 2001
Posts: 3,581
Likes: 28
From: Spring, Texas
Re: 72 heater/defroster function (GaryS)
Chad, how well do think vacuum controlled devices work when my engine is not tunning? :mad Like an idiot (a tired one though) I was testing things with the engine off (hasn't been run in quite a while) and the ignition on. No wonder it didn't work. :smash: It works just fine, thank you, with the engine running.
Gary
Gary
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
Re: 72 heater/defroster function (71'AirStrike)
I just went through this routine on my 78 tho I don't have the wheel. But the hose cluster is similar. I've got a/c but black is the primary source while the green stripe delivers vacuum to the valves that operate the doors.
If you use a vacuum pump...you don't need to pump hard. Except for the water shut-off valve...8-10 pounds will make them move. Actually, its pretty cool to watch all those doors open and close when they are suppose to...it was a slow day!
If you use a vacuum pump...you don't need to pump hard. Except for the water shut-off valve...8-10 pounds will make them move. Actually, its pretty cool to watch all those doors open and close when they are suppose to...it was a slow day!
Thread Starter
Melting Slicks
Joined: May 1999
Posts: 2,897
Likes: 0
From: Moon Township PA
Re: 72 heater/defroster function (LT1driver)
I guess it is a strong arguement for the effects of fatigue. I was really beat that day and was just buttoning up the console. Just a few screws is all it was going to take. :crazy: I finished it up the next day to avoid a repeat.
Gary
Gary
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
Re: 72 heater/defroster function (GaryS)
I find myself doing the same thing...I figured out it was time to quit when console and radio were in place...and I found the dash lip on on the bench! Forgot to secure dash to windshield lip bracket...waited til next day to dis-assembly and get it right!
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