Heater/ac control
Thread Starter
Instructor
Joined: Dec 2012
Posts: 103
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Heater/ac control
I had a new heat/ac control installed, worked great for a couple weeks. Now the heat/cool lever works fine, but it will not change from heat to vent or defrost. I don't seem to have a vacuum leak. Any ideas?
78 L48. Thanks for any help, Mike.
78 L48. Thanks for any help, Mike.
Pro
Joined: Aug 2007
Posts: 707
Likes: 31
From: Pitman NJ
I had mine apart, but I need to take back apart. There are 2 levers, one controls the blend door, the other operates rotary type switch.
When the arm moved, and the rotary switch is turned, it allows vacuum into certain tubes. My guess is that that somehow arm is not turning the switch. If the vacuum lines were off, you would hear it.
To get at it, you need to remove the side panel's of your console. You will probably have to remove the seat to take the panel off.
The water shut off valve is under the hood on the passenger side. It has one line running to its. If this valve is working or not.. it will not effect your AC turning on or not. All it does is stop coolant from running through the heater core when it is not needed
When the arm moved, and the rotary switch is turned, it allows vacuum into certain tubes. My guess is that that somehow arm is not turning the switch. If the vacuum lines were off, you would hear it.
To get at it, you need to remove the side panel's of your console. You will probably have to remove the seat to take the panel off.
The water shut off valve is under the hood on the passenger side. It has one line running to its. If this valve is working or not.. it will not effect your AC turning on or not. All it does is stop coolant from running through the heater core when it is not needed
Pro
Joined: Aug 2007
Posts: 707
Likes: 31
From: Pitman NJ
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
This is the select switch that controls the vacuum function of the heater control. It has had a storied history of being defective since the cars were new and it has carried on in to the reproduction stages as well. The switch is a maze of vacuum passages that are held together by plastic rivet with spring tension on it. The two halves are sealed with a tiny amount of lubricant and will leak.
A cheap fix for this is to put a tiny bit of lubricant inside one of the tubes and then work it back and forth until it seals up. I'd try that with my original one first and hope it works again.
I have the function chart for this switch on my web site listed under the heater control vacuum hose route. This will show you which nipple has vacuum in the different positions.
Willcox
A cheap fix for this is to put a tiny bit of lubricant inside one of the tubes and then work it back and forth until it seals up. I'd try that with my original one first and hope it works again.
I have the function chart for this switch on my web site listed under the heater control vacuum hose route. This will show you which nipple has vacuum in the different positions.
Willcox
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
This is the select switch that controls the vacuum function of the heater control. It has had a storied history of being defective since the cars were new and it has carried on in to the reproduction stages as well. The switch is a maze of vacuum passages that are held together by plastic rivet with spring tension on it. The two halves are sealed with a tiny amount of lubricant and will leak.
A cheap fix for this is to put a tiny bit of lubricant inside one of the tubes and then work it back and forth until it seals up. I'd try that with my original one first and hope it works again.
I have the function chart for this switch on my web site listed under the heater control vacuum hose route. This will show you which nipple has vacuum in the different positions.
Willcox
A cheap fix for this is to put a tiny bit of lubricant inside one of the tubes and then work it back and forth until it seals up. I'd try that with my original one first and hope it works again.
I have the function chart for this switch on my web site listed under the heater control vacuum hose route. This will show you which nipple has vacuum in the different positions.
Willcox
Just changed this part on my 77. Was getting only air out the bottom vents no matter which position the slider was in. $12 part, simple (Two screws easy to get to) to replace with passenger side cover off. Now all positions work as they should.
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Michael S. Palmer
Naples FL
Joined: Jun 2010
Posts: 1,383
Likes: 175
From: FL
my A/C stopped working! fan blows air in all positions but compressor is not getting power. system had been working fine and was retro fitted 10 years ago. Recently recharged to 2.5 lbs. system always blew cold before and after recharge. 1 month ago similar situation: compressor would not engage. played with the contacts and moved selector switch back and forth. this seemed to correct the problem. this lead to having system purged and recharged and checked for leaks. would the blower motor and selector still work but not send power to compressor? does this sound like I need a new switch?
Intermediate
Joined: Feb 2013
Posts: 38
Likes: 0
From: Lake Texoma Oklahoma
On my 79 I have to operate the slider like a safe-cracker would, once I'm sure its in the sweet spot I tug the lever down and the air will blow from the console vents. Even after its been working and after restart I have to tug it again. I need a new vacuum switch.
