Vaccum hose - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Patch** · 08-05-2002, 01:02 AM

I have a question....has anyone made a simplified schematic of the vaccum hose routing for an air conditioned truck? My 72 Blazer has A/C and I need to re-do all of the small vac lines that go from the heater control to every where else. I have the factory assembly manual, but it gets kinda hard to follow. Some of my vac lines are already missing, so It's been a pain to figure it out.
Thanks.....let me know.

*67Fleetsidedream* · 08-05-2002, 08:50 AM

A couple things to remember. When the controls are all the way to the left the air needs to recirculate( middle under where it says "inside" and the bottom on cold). So this means that the passenger side vacuum operated kick panel door needs to be open and the fresh air valve ( under the cowl on the passenger side)needs to be close. When the middle lever is under the "outside" the passenger kick panel door needs to be closed and the fresh air valve (under the cowl on the passenger side) needs to be open.
When you move the lever all the way to the right on "HOT" the heater valve should be open( the vacuum valve that should be on your intake). The fresh air valve and the kick panel vent have to use the same vacuum line. You will have to get a small vacuum "T" to make it one line putting the kick panel vent vacuum motor on one end of the "T", the fresh air valve one one end and enough hose to reach the back of the controller. Then leave it until you find out which port is which on the back of the controller. Then get some vacuum hose and find a vaccum port on your carb. Run that hose to the vaccum ball mounted on the A/C box(under the hood mounted directly the box). Get another peice of hose and connect it to the other port on the vaccum ball. Run this line in to the cab to the back of your controls. This is your main vacuum line. You will need to find out which of the three ports on the back of the controller is the master in. Now run a hose from your heater valve to the back of the controller. This hose will operate the heater valve when the control lever is on "HOT".
You will need to move the hoses around on the ports to figure out which one is main, heat and recurculate.
I hope this helps you out.

Ben

tom hand · 08-05-2002, 10:49 AM

Here's a pic

RodC · 08-05-2002, 11:21 AM

Check out the section in my Chassis manual scans. They are on webshots. Address in sig.

08-05-2002, 01:02 AM	#1
Patch Senior Member Join Date: Jul 2002 Location: Oak Harbor, WA Posts: 709	Vaccum hose I have a question....has anyone made a simplified schematic of the vaccum hose routing for an air conditioned truck? My 72 Blazer has A/C and I need to re-do all of the small vac lines that go from the heater control to every where else. I have the factory assembly manual, but it gets kinda hard to follow. Some of my vac lines are already missing, so It's been a pain to figure it out. Thanks.....let me know. __________________ Patch

08-05-2002, 10:49 AM	#3
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	Here's a pic Attached Images __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

08-05-2002, 11:21 AM	#4
RodC Registered User Join Date: Nov 2001 Location: Fairmont WV Posts: 304	Check out the section in my Chassis manual scans. They are on webshots. Address in sig. __________________ Rod Childers '71 C10 Stepside

08-05-2002, 08:50 AM	#2
67Fleetsidedream Wiseass secured himself a BAN Join Date: Nov 2000 Location: MOON!!! Posts: 2,282	A couple things to remember. When the controls are all the way to the left the air needs to recirculate( middle under where it says "inside" and the bottom on cold). So this means that the passenger side vacuum operated kick panel door needs to be open and the fresh air valve ( under the cowl on the passenger side)needs to be close. When the middle lever is under the "outside" the passenger kick panel door needs to be closed and the fresh air valve (under the cowl on the passenger side) needs to be open. When you move the lever all the way to the right on "HOT" the heater valve should be open( the vacuum valve that should be on your intake). The fresh air valve and the kick panel vent have to use the same vacuum line. You will have to get a small vacuum "T" to make it one line putting the kick panel vent vacuum motor on one end of the "T", the fresh air valve one one end and enough hose to reach the back of the controller. Then leave it until you find out which port is which on the back of the controller. Then get some vacuum hose and find a vaccum port on your carb. Run that hose to the vaccum ball mounted on the A/C box(under the hood mounted directly the box). Get another peice of hose and connect it to the other port on the vaccum ball. Run this line in to the cab to the back of your controls. This is your main vacuum line. You will need to find out which of the three ports on the back of the controller is the master in. Now run a hose from your heater valve to the back of the controller. This hose will operate the heater valve when the control lever is on "HOT". You will need to move the hoses around on the ports to figure out which one is main, heat and recurculate. I hope this helps you out. Ben



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