Heater control vacuum hoses? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chevydog66 · 09-22-2013, 09:05 PM

I'm not sure which vacuum hose goes where on the heater contol vacuum switch because I am not getting vacuum to the heater valve or flapper doors. I have a 72 GMC with factory a/c and it has 3 ports on the vacuum switch. 1 of them is plugged. It's a real p-i-t-a to get to it also. I just repainted and rebuilt the whole truck so I just marked the lines when I removed them. I also installed new vac hoses as well. If you are looking up at it the hose closest to the front of the truck is blocked off and always has been. Is this correct? IIRC the ports are labeled 1,2,3. Also, which port do I connect to vacuum canister?

1972SUPERSB · 09-22-2013, 09:27 PM

I had to do this also. Here is a pic that should help.
Posted via Mobile Device
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chevydog66 · 09-22-2013, 09:49 PM

I have that pic. Just not sure which hose goes where.

1972SUPERSB · 09-22-2013, 09:52 PM

Quote:

Originally Posted by chevydog66

I have that pic. Just not sure which hose goes where.

How I did it was hook all them up on the 3 ports and to the other components like the picture shows. When you turn the lever to AC you should get vacuum to the hose that's going to the heater valve. If you don't you need to swap the hoses on the AC lever
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1972SUPERSB · 09-22-2013, 09:53 PM

Do you have vacuum coming from engine to the vacuum canister?
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chevydog66 · 09-22-2013, 10:30 PM

Quote:

Originally Posted by 1972SUPERSB

Do you have vacuum coming from engine to the vacuum canister?
Posted via Mobile Device

Yes. No vacuum at heater valve or either vent door.

1972SUPERSB · 09-22-2013, 10:44 PM

Quote:

Originally Posted by chevydog66

Yes. No vacuum at heater valve or either vent door.

I'll check mine in a minute and see where my hoses go
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chevydog66 · 09-23-2013, 10:12 PM

Ok. thanks!! I'll tear into it one of these days that I don't have to work 11 hours.

chevydog66 · 09-25-2013, 12:04 PM

Ok I have 16" at middle switch port. 3" at right kick panel pod which isn't moving. Barely 1" @ cowl pod and 0" @ heater valve. Guess I need a new vac switch on the heater?
Posted via Mobile Device

09-22-2013, 09:05 PM	#1
chevydog66 GM ONLY BABY!!! Join Date: Oct 2003 Location: Fort Wayne, IN. Posts: 1,998	Heater control vacuum hoses? I'm not sure which vacuum hose goes where on the heater contol vacuum switch because I am not getting vacuum to the heater valve or flapper doors. I have a 72 GMC with factory a/c and it has 3 ports on the vacuum switch. 1 of them is plugged. It's a real p-i-t-a to get to it also. I just repainted and rebuilt the whole truck so I just marked the lines when I removed them. I also installed new vac hoses as well. If you are looking up at it the hose closest to the front of the truck is blocked off and always has been. Is this correct? IIRC the ports are labeled 1,2,3. Also, which port do I connect to vacuum canister? __________________ 2 wrongs don't make a right, but 3 lefts do. 66 Chevelle Malibu 406ci, 573hp, 10.99@121mph 96 Chevy Silverado Z71 72 GMC 1500 Super Custom LS 6.0/4L65 on airride http://www.cardomain.com/ride/707879...mc-c-k-pick-up

09-22-2013, 09:27 PM	#2
1972SUPERSB Registered User Join Date: Sep 2012 Location: San Antonio, TX Posts: 1,026	Re: Heater control vacuum hoses? I had to do this also. Here is a pic that should help. Posted via Mobile Device Posted via Mobile Device Attached Images __________________ Jeff 1972 Cheyenne Super SWB 350, Auto, Bucket Seats w/Console, Tach, Factory A/C, P/S ,P/B, Tilt 1998 Chevy 1500 Ext Cab 5.7, Pewter w/blue interior

09-22-2013, 09:49 PM	#3
chevydog66 GM ONLY BABY!!! Join Date: Oct 2003 Location: Fort Wayne, IN. Posts: 1,998	Re: Heater control vacuum hoses? I have that pic. Just not sure which hose goes where. __________________ 2 wrongs don't make a right, but 3 lefts do. 66 Chevelle Malibu 406ci, 573hp, 10.99@121mph 96 Chevy Silverado Z71 72 GMC 1500 Super Custom LS 6.0/4L65 on airride http://www.cardomain.com/ride/707879...mc-c-k-pick-up

09-22-2013, 09:53 PM	#5
1972SUPERSB Registered User Join Date: Sep 2012 Location: San Antonio, TX Posts: 1,026	Re: Heater control vacuum hoses? Do you have vacuum coming from engine to the vacuum canister? Posted via Mobile Device __________________ Jeff 1972 Cheyenne Super SWB 350, Auto, Bucket Seats w/Console, Tach, Factory A/C, P/S ,P/B, Tilt 1998 Chevy 1500 Ext Cab 5.7, Pewter w/blue interior

09-23-2013, 10:12 PM	#8
chevydog66 GM ONLY BABY!!! Join Date: Oct 2003 Location: Fort Wayne, IN. Posts: 1,998	Re: Heater control vacuum hoses? Ok. thanks!! I'll tear into it one of these days that I don't have to work 11 hours. __________________ 2 wrongs don't make a right, but 3 lefts do. 66 Chevelle Malibu 406ci, 573hp, 10.99@121mph 96 Chevy Silverado Z71 72 GMC 1500 Super Custom LS 6.0/4L65 on airride http://www.cardomain.com/ride/707879...mc-c-k-pick-up

09-25-2013, 12:04 PM	#9
chevydog66 GM ONLY BABY!!! Join Date: Oct 2003 Location: Fort Wayne, IN. Posts: 1,998	Re: Heater control vacuum hoses? Ok I have 16" at middle switch port. 3" at right kick panel pod which isn't moving. Barely 1" @ cowl pod and 0" @ heater valve. Guess I need a new vac switch on the heater? Posted via Mobile Device __________________ 2 wrongs don't make a right, but 3 lefts do. 66 Chevelle Malibu 406ci, 573hp, 10.99@121mph 96 Chevy Silverado Z71 72 GMC 1500 Super Custom LS 6.0/4L65 on airride http://www.cardomain.com/ride/707879...mc-c-k-pick-up

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