Heater control valve question

[lowreese26]

A heater hose just blew on my 96 Silverado. And while trying to find information on replacement I realized that the heater control valve has been removed. That would explain why my heat has never worked. Just thought it had a clogged heater core. Putting it back on looks pretty straight forward, except the vacuum line. Where does the go to?

 

[lowreese26]

So I just found this. But the part where the line plugs in is missing too . Anybody know what that part is called?

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[lowreese26]

Can someone tell me what number 19 is called?

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[tinfoil_hat]

You have a vacuum switch there on the firewall. One line runs to the heater valve as you can see, the the other hose barb on the valve runs over to a dashpot on the driver's side of the upper intake manifold. It's supposed to be a hard line running over the top of the intake with a bend around the throttle body. That hard line gets brittle with age and heat. Just run a hose instead.

Here is the heater vacuum valve from your diagram:
https://www.rockauto.com/en/catalog...+air+conditioning,heater+valve+solenoid,16375

 

[lowreese26]

Thanks tinfoil_hat. I got one more question/favor. Any chance you could take a picture or tell me where the wiring for the plug in the heater valve solenoid comes from? I appreciate all the help

 

[tinfoil_hat]

I will look when I get home if someone does not beat me to it. I think it pigtails off the big harness that goes through the firewall under the coolant reservoir.

 

[lowreese26]

Any chance you had a second to look?

 

[east302]

I'm 99% sure that the pickups did not have the heater valve, only the Suburbans/Tahoe.

The heater valve has a vacuum line that connects to the solenoid on the firewall. When the a/c control panel temperature dial is set to the full cold detent, the solenoid is powered (from the control panel) and vacuum closes the heater valve.

This, in theory, provides maximum cooling by keeping the coolant from always going through the heater core.

My 1998 K1500 truck does not have it (the heater hoses are routed straight to the heater core connections) but my 1998 Tahoe does have the valve and solenoid.

This isn't my truck, but mine looks like this...no valve, solenoid or its hard vacuum line running across the intake:

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The wiring diagram for 1998 calls for that valve only on the SUV models.

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Heater valve and solenoid on Tahoe:

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To answer your question, the wiring for the solenoid comes from the bulk harness that goes against the firewall, penetrating at the driver side and under the coolant reservoir. From the bulk wiring, a single bundle comes off near the accumulator. It then splits into three pigtails...one goes to the MAF sensor, one to the water/heater valve solenoid and one to the underhood light.






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[tinfoil_hat]

Yep. Perfect explanation. I forgot my burb has a lot more plumbing than a pickup.

 

[lowreese26]

Awesome. So then any thought on why my heat has never worked? Clogged heater core?