ac vacuum lines

[89Suburban]

Here is a pic of the rear of the vacuum plug that connects to the control switch. Note the open tabs on each side. They slide over 2 plastic studs on the back of the switch and there are 2 of those spring steel stamped washer things that you push on and thy hold but are a bitch to remove. Most of the time the studs break on me but that will not hurt anything the harness does pretty good on its own holding onto the switch.

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Here is a step by step you can print out and see if this helps you on your quest. You can also download onto your smart phone so you have it on hand. I have been doing this lately on any projects I been having to tackle.

AC, Heat, Vacuum, Harness, Hoses, Servo, Diagnosis, Troubleshooting, Diagram, Switch

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[82chevy350]

OK so i got one hose i couldn't find where it went. Its red and was real brittle due to age it connected to a black line from the switch.I believe its 175 from the page that has the breakdown of the housing you posted. Does this thing really go down in that housing the reason i ask is i really don't wanna pull the housing again as i did it about 2 weeks ago to replace my heater core. I didn't actually think on to why my air was blowing out all the vents while i had air blowing. I owned this truck for six years now haha then i had looked up on how it worked.

 

[chengny]

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[89Suburban]

OK so i got one hose i couldn't find where it went. Its red and was real brittle due to age it connected to a black line from the switch.I believe its 175 from the page that has the breakdown of the housing you posted. Does this thing really go down in that housing the reason i ask is i really don't wanna pull the housing again as i did it about 2 weeks ago to replace my heater core. I didn't actually think on to why my air was blowing out all the vents while i had air blowing. I owned this truck for six years now haha then i had looked up on how it worked.

No hoses go to the actual inside of the heater box. The actuator #175 that you are talking about is mounted on the back of the box. You can probably reach behind there and feel it and the nipple the hose slips onto. Sounds like somebody patched that line with a different colored hose?

 

[roundhouse]

thanks for posting up the diagrams.

we're installing A/C from a 82 diesel donor, into a 77~80 driver for my 16 yr old son

the 77~80 has a state issued VIN and so far weve been unable to locate the VIN stamp in the frame, so we have no idea what year it actually is.

 

[chengny]

Vacuum hose and wiring diagrams (1977-1980 the same):

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[franklin]

gray supply hose

The gray supply hose should come from under the hood, from a vacuum pot or reservoir. It prevents the doors from moving, when you accelerate or put your foot in it , and the engine vacuum drops. The reservoir maintains the vacuum and has a check valve to close when the engine vac is lower than in the pot. I am working on a 79 C-20. I have one actuator I haven't found yet.
The hose is laying loose under the dash not hooked to anything. Some years had a heater control valve that was actuated from the controller. The line I found may have been plugged and not had that option.

 

[1low4x4]

Thank god i found this thread

 

[chengny]

and there are 2 of those spring steel stamped washer things that you push on and thy hold but are a bitch to remove. Most of the time the studs break on me


Early on (after snapping off a few posts - and losing dozens of the Jesus clips), I figured there must be a better method of removing them than just trying to pry them off.

There is ( a better method). Screw them off - like they were little round nuts.

Insert the tip of a small screwdriver under one side of the Jesus clip (and create a light force in the upward direction). That tilts the clip. While maintaining that pressure and tilt, rotate the clip. Generally you can use your fingertips.

The sharp inner edges of the clip will start to cut tiny threads on the post as it rotates and it will begin to climb. Usually you only have to get it started and then you can remove the screwdriver. Keep turning the clip and it will thread right off.

My wife says I need to get a job.

 

[GTME94]

Jerry, You have a job, you help everyone else on this forum. It's just that the pay sux!

 

[1low4x4]

Thats what worked for me, turning them like nuts on the shaft.

That sounded odd.

Anyways, great info in this thread. Allowed me to trace things out today

 

[VAL]

Here is a pic of the rear of the vacuum plug that connects to the control switch. Note the open tabs on each side. They slide over 2 plastic studs on the back of the switch and there are 2 of those spring steel stamped washer things that you push on and thy hold but are a bitch to remove. Most of the time the studs break on me but that will not hurt anything the harness does pretty good on its own holding onto the switch.

You must be registered for see images

Here is a step by step you can print out and see if this helps you on your quest. You can also download onto your smart phone so you have it on hand. I have been doing this lately on any projects I been having to tackle.

AC, Heat, Vacuum, Harness, Hoses, Servo, Diagnosis, Troubleshooting, Diagram, Switch

You must be registered for see images

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Does anyone know where I can get a complete new vacuum line harness from the selector to the actuators? I've been looking with no luck.

 

[flyboy1100]

What is this disc that was talked about? Mine quit working today

 

[flyboy1100]

And i think my vacuum is hooked directly to manifold, rather then the vacuum canister, should it be connected to the canister?

 

[chengny]

What is this disc that was talked about?


The HVAC selector switch is actually a miniature multiport valve and the disc with the grooves in it like the "plug". Larger versions of multiport valves are commonly used in swimming pool plumbing systems and hydraulic controls.

When the disc/plug is rotated from one setting to another, the grooves are realigned and change the inter-connections between the various external ports. The allows a single supply source to be directed to a number of different ports, connect a port to a port, stop flow to a port, etc - with the use of a single valve.

In this case the manifold vacuum supply is connected to the selector valve on port #1. When you slide the selector lever left and right, the disc rotates within the valve body and the connections between the ports change accordingly.

And i think my vacuum is hooked directly to manifold, rather then the vacuum canister, should it be connected to the canister?

The supply tubing to the HVAC control system should originate at the manifold and pass through a check valve. After the check valve the line is tee'd to the left and right (as looking at the cab).

The right side of the tee is connected to the vacuum reservoir.
The left side passes through the firewall and is ultimately connected to the #1 port on the control panel (via the gray tubing).