AC vacuum control head Q. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Trackman101 · 05-28-2018, 02:04 PM

By design should the ac vacuum controller switch hold vacuum in the ac position even when the truck is shut off? Mine doesn't , I am trying to test to see if the switch is leaking.
My engine doesn't make a bunch of vacuum and when I am doing some spirited driving (ac on) my vac canister doesn't have enough supply to keep my heater valve closed. When the truck is idling or cruising I have enough vacuum to keep it closed. I have confirmed my canister holds vacuum, no leaks at the heater or door vent diaphragms.I have the 2nd vac port on the head plugged.

Andy4639 · 05-28-2018, 02:45 PM

Quote:

Originally Posted by Trackman101

By design should the ac vacuum controller switch hold vacuum in the ac position even when the truck is shut off? Mine doesn't , I am trying to test to see if the switch is leaking.
My engine doesn't make a bunch of vacuum and when I am doing some spirited driving (ac on) my vac canister doesn't have enough supply to keep my heater valve closed. When the truck is idling or cruising I have enough vacuum to keep it closed. I have confirmed my canister holds vacuum, no leaks at the heater or door vent diaphragms.I have the 2nd vac port on the head plugged.

Invest in a vacuum can and it should be good to go. Put a check valve in line so it can't bleed off.

Trackman101 · 05-28-2018, 03:42 PM

I have the stock vacuum canister. It works as it should. I can't seem to find anyone who sells just that vacuum switch.

**dmjlambert** · 05-28-2018, 04:45 PM

What port are you getting vacuum from on the carburetor, or are you getting it from the intake manifold? Can you show a picture of where the vacuum line is connected to the engine? Do you think the vacuum switch on the A/C controller is leaking because you hear a hiss from it, or do you think something else is going on?

Trackman101 · 05-28-2018, 05:47 PM

I've isolated down to the vacuum switch. Now to track one down without having to buy the whole a/c heater switch assembly.

Andy4639 · 05-28-2018, 09:28 PM

Manes truck parts use to have them.

**Steeveedee** · 05-28-2018, 11:11 PM

I've bought the vacuum switch from local AC shops that have a parts department open to the public. Even at retail, they aren't that pricey.

Trackman101 · 06-01-2018, 09:01 AM

I struck out trying to find just the vacuum switch. I did score an ol ac/heater switch assembly for cheap and stole the vac switch off of it. I've got it back together yesterday and tested. This morning the system is still holding vacuum. Fixed!

05-28-2018, 02:04 PM	#1
Trackman101 Registered User Join Date: Jul 2015 Location: Alberta Posts: 161	AC vacuum control head Q. By design should the ac vacuum controller switch hold vacuum in the ac position even when the truck is shut off? Mine doesn't , I am trying to test to see if the switch is leaking. My engine doesn't make a bunch of vacuum and when I am doing some spirited driving (ac on) my vac canister doesn't have enough supply to keep my heater valve closed. When the truck is idling or cruising I have enough vacuum to keep it closed. I have confirmed my canister holds vacuum, no leaks at the heater or door vent diaphragms.I have the 2nd vac port on the head plugged. Last edited by Trackman101; 05-28-2018 at 02:16 PM.

05-28-2018, 03:42 PM	#3
Trackman101 Registered User Join Date: Jul 2015 Location: Alberta Posts: 161	Re: AC vacuum control head Q. I have the stock vacuum canister. It works as it should. I can't seem to find anyone who sells just that vacuum switch.

05-28-2018, 04:45 PM	#4
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 3,563	Re: AC vacuum control head Q. What port are you getting vacuum from on the carburetor, or are you getting it from the intake manifold? Can you show a picture of where the vacuum line is connected to the engine? Do you think the vacuum switch on the A/C controller is leaking because you hear a hiss from it, or do you think something else is going on?

05-28-2018, 05:47 PM	#5
Trackman101 Registered User Join Date: Jul 2015 Location: Alberta Posts: 161	Re: AC vacuum control head Q. I've isolated down to the vacuum switch. Now to track one down without having to buy the whole a/c heater switch assembly.

05-28-2018, 09:28 PM	#6
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: AC vacuum control head Q. Manes truck parts use to have them. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

05-28-2018, 11:11 PM	#7
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,090	Re: AC vacuum control head Q.I I've bought the vacuum switch from local AC shops that have a parts department open to the public. Even at retail, they aren't that pricey. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

06-01-2018, 09:01 AM	#8
Trackman101 Registered User Join Date: Jul 2015 Location: Alberta Posts: 161	Re: AC vacuum control head Q. I struck out trying to find just the vacuum switch. I did score an ol ac/heater switch assembly for cheap and stole the vac switch off of it. I've got it back together yesterday and tested. This morning the system is still holding vacuum. Fixed!



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