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#1 |
Registered User
Join Date: Jan 2007
Location: Keller, TX
Posts: 143
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Heater Hose Question
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
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Texas - Don't Let The Size Scare You! |
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#2 |
Senior Member
Join Date: Feb 2006
Location: Las Vegas
Posts: 1,378
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Re: Heater Hose Question
Are your small vacuum hoses installed correctly?
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1972 Chevrolet Blazer 4x4 (Almost done stay tuned) 1970 Chevrolet Pickup Longhorn CST/20 (SOLD) |
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#3 |
Registered User
Join Date: Aug 2010
Location: Edwards, CA
Posts: 7,503
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Re: Heater Hose Question
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.
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Thanks, Tim * VIN/Model Decoders * Power Team Charts (engine/transmission/gear ratio) * Post Your Pickup SPID ** Blazer SPID ** Suburban/Panel SPID * RTFM ... Read The Factory Manuals... download 'em here Highlanders ** Do you have a 1972 Plaid Pickup? ** Plaid Blazer ** Plaid Suburban |
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#4 |
Registered User
![]() Join Date: Dec 2012
Location: Chandler AZ
Posts: 1,149
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Re: Heater Hose Question
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.
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1970 Longhorn, Front Disc, 350/4 bolt, 882 heads, HEI, Edelbrock, 700R4, HO-52/4.11. 1996 Corvette, Collector Roadster, LT4, 396, 450RWHP, 6sp, 4.11/Dana44/posi 5 point roll bar And let us not grow weary of doing good, for in due season we will reap, if we do not give up. Gal 6:9 |
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#5 |
Registered User
Join Date: May 2004
Location: Topeka, Ks
Posts: 2,293
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Re: Heater Hose Question
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
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I'm not a pessimist, I'm just optimistic that bad things are going to happen. 1971 Cheyenne Super K10 - tilt, cruise, air, am/fm, tow hooks, factory buckets! 1986 Jeep J10 pickup, - 5.3L Vortec with 4L60e and NP241. |
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#6 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: Heater Hose Question
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
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1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#7 |
One of the First
![]() Join Date: Jan 2000
Location: St. Augustine,FL.
Posts: 4,054
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Re: Heater Hose Question
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.
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DAVID PASSMORE ST AUGUSTINE ,FL ZIP 32084 '71 SWB K/10 CUSTOM DELUXE (Chili) '72 BLAZER K/5 Muscle Truck (Mule) '72 LWB K/20 CHEYENNE (Blackie) |
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#8 | |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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![]() Quote:
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. ![]() ![]() ![]() ![]()
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#9 |
One of the First
![]() Join Date: Jan 2000
Location: St. Augustine,FL.
Posts: 4,054
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Re: Heater Hose Question
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
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DAVID PASSMORE ST AUGUSTINE ,FL ZIP 32084 '71 SWB K/10 CUSTOM DELUXE (Chili) '72 BLAZER K/5 Muscle Truck (Mule) '72 LWB K/20 CHEYENNE (Blackie) |
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