Where does this vacuum line go ??

[8thNote]

New to me 96 'Burb 1500 5.7 vortec. I'm in the process of blocking off the rear ac lines. I pulled out the air filter housing to access them and found this vacuum operated device that is plumbed into the Heater hoses. The small vacuum line coming off of the valve is extremely dry rotted and I cant tell where it's supposed to hook up. Any help is appreciated. It's on the passenger side of the engine bay and is plumbed in between 2 heater hoses.

 

[HotWheelsBurban]

That device is the heater control valve. Suburbans have those, for the rear heat and AC. The line should connect to the intake manifold somewhere. I have a Burb, but we're not currently driving it so it's not where I can look at it.

 

[454cid]

I think you'll find a contraption mounted someplace like the firewall plugged into the electrical system, and also has a vacuum port on it. I've never seen the system, but when I was researching putting it on my truck, I read that the GMT-400 HVAC system switches the vacuum electrically.... which makes sense sense since all but the very early ones are electrical. Some were mechanical, but none of them were vacuum like my old Buicks.

It's either the same part, or similar to what some older 4x4's used to engage 4wd (Dodge, I think?)

 

[east302]

The hard line (picture) comes from the PCV fitting on the driver side and goes to a solenoid valve on the firewall near the accumulator.

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Your vacuum line goes from that solenoid to the water valve - the line that you’re holding.

When the “Max” detent is selected on the a/c temperature dial, the solenoid is energized and vacuum is applied to the water valve. The valve closes, shutting off coolant flow to the heater core to maximize a/c performance.

 

[8thNote]

The hard line (picture) comes from the PCV fitting on the driver side and goes to a solenoid valve on the firewall near the accumulator.

You must be registered for see images attach

Your vacuum line goes from that solenoid to the water valve - the line that you’re holding.

When the “Max” detent is selected on the a/c temperature dial, the solenoid is energized and vacuum is applied to the water valve. The valve closes, shutting off coolant flow to the heater core to maximize a/c performance.

Thanks, I found it. It's on the firewall right behind the AC dryer/receiver. It has 2 vacuum ports. The top one goes to the hard line to pcv that you mentioned and the bottom one goes to this valve.