Heater Hose Question

[KellerMAC]

After my rebuild, I just recently recharged my factory AC unit in my 72 C10 and it blows cold but once the truck heats up, I am getting some hot air in my vents. I have a new heater control valve on the inner fender wall, but it seems to let hot water by. I installed a in-line cut-off valve and that cured the problem, but I don't like that solution. Why would the heater control valve not do it's job?

All comments welcomed.

Thanks

KellerMac

[Luis_gz06]

Are your small vacuum hoses installed correctly?

[SS Tim]

Did you test the "new" valve prior to installing it? Sounds like there may be an issue with the lines or vacuum switch controlling the valve. Do you have the factory service manual for 72? It has a very comprehensive section on the A/C system.

[Longhorn 70]

KellerMac,

Are you certain you
1. Have enough vaccuum at the source, i.e. the vaccuum switch on the control.
2. Does the vaccuum get to the valve? Look for broken T's or hoses.

If you have a vaccuum gauge you can check at the valve to verify the little vaccuum switch on the control works.

Also I seem to remember, back when I worked auto parts, there are 2 different valves that look similar. One opens on vaccuum the other closes. They look very similar.

[chipflyer]

There are 2 styles of heater control water valves. One is normaly open with vacuum applied and one is closed with vacuum applied, you have the wrong one. I can't remember for sure what year this changed or why but if you search this site I think you will find more info about this.

Jeff
Posted via Mobile Device

[JimKshortstep4x4]

Jeff is right about the two vacuum hose routings. The best thing to do is to check your routing against these two schematics to determine if you have the right water control valve.

Jim

[D.PASSMORE]

A/C trucks/Blazers had the big diverter box under dash. Inside the box - is whats called the "flapper" door. They are notorious for not closing all the way. Or, the flimsey hinge set-up cracks/breaks and it never seals properly. That is where my heat was getting into my cold air. I replaced the diverter box / problem solved.

[Andy4639]

Originally Posted by D.PASSMORE

A/C trucks/Blazers had the big diverter box under dash. Inside the box - is whats called the "flapper" door. They are notorious for not closing all the way. Or, the flimsey hinge set-up cracks/breaks and it never seals properly. That is where my heat was getting into my cold air. I replaced the diverter box / problem solved.

This has nothing to do with the hot water getting to the heater core. If you have hot air coming inside the truck the flapper did nothing but redirect it. The problem is either the heater core water valve isn't working are there is hot air coming around the evaperator and not through it in the housing are the gaskets are no good letting hot engine air into the system at the fire wall.
I have both in mine. I have a manual shut off I close during the summer months and the AC blows 38 degree's no matter what the air temp is.

[D.PASSMORE]

I understand, but it solved my problem with hot air coming out my vents. So it appears that I just got lucky and fixed mulitple problems. Kool!
Posted via Mobile Device