Where is the ac/heater water valve?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

starbuckk · 01-31-2004, 11:57 PM

Probably a stupid question but where is the water cut off valve on a 1968 C20? I seem to have located everything BUT that. I got a replacement valve but for some silly reason I can't find where the thing is located! I may not even need to replace it, since it is vacuum actuated and I've replaced most of the vacuum lines.

But I don't have any unconnected vacuum lines so I can't trace to the darn thing. This indicates to me that it isn't hooked up at all, which is probably why I"m always getting heat out of the vents.

I've got both of the vent actuators hooked up and working properly. I just can't find the water valve.

s95930 · 02-01-2004, 12:06 AM

On my 70 it is on the inner fender on the passenger side. Should be able to trace the heater hoses to find it.

starbuckk · 02-01-2004, 12:20 AM

I think 67-69 might have been different. The hoses go directly from the water pump into the firewall, so it is on the passenger side of the firewall, but it appears that they must be inside the venting system somewhere. I'm guessing I have to pull the vent connections somewhere but don't want to tear into it until I know exactly which one to pull since it appears to be quite an effort.

I looked for it when I replaced the AC-heater selector box but couldn't find it then either.

Now, this truck has been through a few different hands before it got to me. Is it possible that it should be in FRONT of the firewall and someone just removed it??

You said on the inner fender..meaning in the engine compartment? If thats the case, then someone has removed the cut-off on mine completely and that would be why I can't find the thing.

walker · 02-01-2004, 01:06 AM

My '67 C-10 does not have a water valve, pretty sure it wasn't removed and bypassed. There is also no vaccum line for it. Maybe it was not on all trucks or not until a later model year.

Baradium · 02-01-2004, 01:15 AM

If you get one it goes on the fender as mentioned. It seems that they didn't all get one as there is a flap to shut off air flow through the heater core and redirect it (bypassing it) when the heater knob is off.

Might have been something they just put on if you had A/C.

starbuckk · 02-01-2004, 01:32 AM

The LMC catalog shows four different water valves. There are two possible types for 67-72 without A/C, none are vacuum controlled.

For models with A/C, there is one for 67-69 and a slightly different one for 70-72. Both are vacuum controlled.

Just saw another thread here with a vacuum diagram that seems to indicate that the cutoff valve should indeed be in front of the firewall. This would indicate that it is missing on my truck.

http://67-72chevytrucks.com/vboard/s...threadid=88218

Also from looking at that thread I think I have my vacuum lines hooked up wrong. This would probably explain a few things.

The problem I am having is that the A/C performance is weekend because some air is still getting through the heater core.

Woody · 02-02-2004, 01:06 PM

The Vacuume controled water valve was located either on the pass. side inner fender or it was mounted in the Intake where the heater hose nipple is.

Speaking of nipples!!!!!Did you see the 1/2 time show??LOL

The valve that goes on the intake is about 6" tall to clear the a/c bracket.

I like the look and fit of the valve mounted on the inner fender. It looks better and is easier to change if needed.

starbuckk · 02-22-2004, 04:19 AM

Seems there is no one standard answer to this question. The service manual (which I just got last week), doesn't show ANY water cut off. Intent seems to be for water to be running through the heater core at all times and the only thing keeping heated air from entering the cab is a vent flap that doesn't seem to close all the way.

But, I've seen a couple of pictures posted here that did in fact have these cutoff valves. Here is a recent thread that has a picture of one that uses the style of cut off valve like what LMC sells for the 67-69. Note the feed line originating from the thermostat area of the block.

http://67-72chevytrucks.com/vboard/s...threadid=91060

The 70-72 version has an angled input line, apparently designed for water lines originating and terminating at the water pump. The two differences being the input pipe is angled and there is a bracket to mount it on the fender.

So, given that my truck is on what I believe to be its third engine, which is configured as the later model, I guess I should have ordered the later version of the cut off valve. Now I get to try to make do with what I have.

I definitely need to do something..the a/c is competing with the heater core.

01-31-2004, 11:57 PM	#1
starbuckk Registered User Join Date: Jan 2004 Location: Hanford CA Posts: 22	Where is the ac/heater water valve?? Probably a stupid question but where is the water cut off valve on a 1968 C20? I seem to have located everything BUT that. I got a replacement valve but for some silly reason I can't find where the thing is located! I may not even need to replace it, since it is vacuum actuated and I've replaced most of the vacuum lines. But I don't have any unconnected vacuum lines so I can't trace to the darn thing. This indicates to me that it isn't hooked up at all, which is probably why I"m always getting heat out of the vents. I've got both of the vent actuators hooked up and working properly. I just can't find the water valve.

02-01-2004, 12:06 AM	#2
s95930 A-Adam A-Adam Join Date: Apr 2003 Location: Sarpy Co. Ne. South of Omaha Posts: 263	On my 70 it is on the inner fender on the passenger side. Should be able to trace the heater hoses to find it. __________________ 70 3/4 ton GMC Camper Special

02-01-2004, 01:06 AM	#4
walker Registered User Join Date: Jul 2003 Location: north of Phx AZ about 30 miles Posts: 698	My '67 C-10 does not have a water valve, pretty sure it wasn't removed and bypassed. There is also no vaccum line for it. Maybe it was not on all trucks or not until a later model year. __________________ Andy,Phx AZ '67 C-10 (Ahhh, done at last. Well there is that disk front end I want to put in and...) "23 C-Cab-sold '48 Ford 8N tractor(still working) '67 Scout(Now on the road) '70 MG B.-sold

02-22-2004, 04:19 AM	#8
starbuckk Registered User Join Date: Jan 2004 Location: Hanford CA Posts: 22	Seems there is no one standard answer to this question. The service manual (which I just got last week), doesn't show ANY water cut off. Intent seems to be for water to be running through the heater core at all times and the only thing keeping heated air from entering the cab is a vent flap that doesn't seem to close all the way. But, I've seen a couple of pictures posted here that did in fact have these cutoff valves. Here is a recent thread that has a picture of one that uses the style of cut off valve like what LMC sells for the 67-69. Note the feed line originating from the thermostat area of the block. http://67-72chevytrucks.com/vboard/s...threadid=91060 The 70-72 version has an angled input line, apparently designed for water lines originating and terminating at the water pump. The two differences being the input pipe is angled and there is a bracket to mount it on the fender. So, given that my truck is on what I believe to be its third engine, which is configured as the later model, I guess I should have ordered the later version of the cut off valve. Now I get to try to make do with what I have. I definitely need to do something..the a/c is competing with the heater core. __________________ 1968 C-20 Custom Camper package Chevy Red (iow: orange!)

02-01-2004, 12:20 AM	#3
starbuckk Registered User Join Date: Jan 2004 Location: Hanford CA Posts: 22	I think 67-69 might have been different. The hoses go directly from the water pump into the firewall, so it is on the passenger side of the firewall, but it appears that they must be inside the venting system somewhere. I'm guessing I have to pull the vent connections somewhere but don't want to tear into it until I know exactly which one to pull since it appears to be quite an effort. I looked for it when I replaced the AC-heater selector box but couldn't find it then either. Now, this truck has been through a few different hands before it got to me. Is it possible that it should be in FRONT of the firewall and someone just removed it?? You said on the inner fender..meaning in the engine compartment? If thats the case, then someone has removed the cut-off on mine completely and that would be why I can't find the thing.

02-01-2004, 01:15 AM	#5
Baradium Binder Rep Join Date: Jan 2001 Location: Salcha, AK Posts: 1,506	If you get one it goes on the fender as mentioned. It seems that they didn't all get one as there is a flap to shut off air flow through the heater core and redirect it (bypassing it) when the heater knob is off. Might have been something they just put on if you had A/C.

02-01-2004, 01:32 AM	#6
starbuckk Registered User Join Date: Jan 2004 Location: Hanford CA Posts: 22	The LMC catalog shows four different water valves. There are two possible types for 67-72 without A/C, none are vacuum controlled. For models with A/C, there is one for 67-69 and a slightly different one for 70-72. Both are vacuum controlled. Just saw another thread here with a vacuum diagram that seems to indicate that the cutoff valve should indeed be in front of the firewall. This would indicate that it is missing on my truck. http://67-72chevytrucks.com/vboard/s...threadid=88218 Also from looking at that thread I think I have my vacuum lines hooked up wrong. This would probably explain a few things. The problem I am having is that the A/C performance is weekend because some air is still getting through the heater core.

02-02-2004, 01:06 PM	#7
Woody Registered User Join Date: Feb 2000 Location: Georgetown, KY, USA Posts: 631	The Vacuume controled water valve was located either on the pass. side inner fender or it was mounted in the Intake where the heater hose nipple is. Speaking of nipples!!!!!Did you see the 1/2 time show??LOL The valve that goes on the intake is about 6" tall to clear the a/c bracket. I like the look and fit of the valve mounted on the inner fender. It looks better and is easier to change if needed.



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