Heater hose shutoff valves make drastic difference!
Melting Slicks
Joined: Oct 2004
Posts: 2,662
Likes: 8
From: Knoxville Tennessee
Bob,
I'm sorry I got a little heated on this but I have seen too many people complain of very hot conditions in their C3's and have experimented with the original equipment checked how it works and know that there are things that can be done to vastly improve the comfort level in the car. Nothing against GM or wanting to keep the cars original. But I want to drive my car long distance and be comfortable doing it. The only way to accomplish that was to make some changes to the system. The system has inherent flaws that compromise its ability to cool the car and keep the heat out. The research that has been done shows how to overcome the flaws and make it work. God bless all of you and pray that God continues to bless this country and our forum friends all over the world.
Bernie
I'm sorry I got a little heated on this but I have seen too many people complain of very hot conditions in their C3's and have experimented with the original equipment checked how it works and know that there are things that can be done to vastly improve the comfort level in the car. Nothing against GM or wanting to keep the cars original. But I want to drive my car long distance and be comfortable doing it. The only way to accomplish that was to make some changes to the system. The system has inherent flaws that compromise its ability to cool the car and keep the heat out. The research that has been done shows how to overcome the flaws and make it work. God bless all of you and pray that God continues to bless this country and our forum friends all over the world.
Bernie
Burning Brakes
Joined: Nov 2004
Posts: 1,193
Likes: 176
From: Hillsborough NC
I think the stock system is more than adequate when properly refurbished and running correctly. Having said that, it is not an easy task on such old cars.
I recently redid my entire system in my 78 and it functions perfectly and is very cool. To get to this level, I had to disassemble the entire interior and re-seal the whole set of ducts as well as make some ducts where GM fell short (Ther was a 1" gap between my defroster duct on the control unit and the duct in the top of the dash). You wouldn't believe how much air leaks out of this system behind the dash when it is poorly sealed.
Once sealed, the system blew very cold air (and lots of it, no need for a C4 blower motor here).
Remember, these A/C systems were used in GM cars with two and three times the interior space. There should be plenty of cooling power for our small cockpits. Nine times out of Ten, the issue has to be in the delivery mechanism of the cool air.
I'm not saying there isn't room for improvement. The shutoff valve is definitely a weak point for several reasons. The control circuit is weak at best and doesn't really hold the valve shut unless you are in the max cold position, and the fact that it is only in one of the heater core lines is also a problem. Heat from the other line does naturally bleed into the core around the valve. Someone posted a thread where they used a valve from a Ford Explorer (I Think) as a replacement. The Ford valve not only shuts off the water, but redirects it back to the engine through the return line, completely isolating the core. A clever solution which retains the functionality and improves on the system.
Heater cores and vacuum circuits are not as flashy as cam specs and carb jetting, but they are just as challenging and rewarding to get running correctly. I find the challenge of making the old systems work to be a lot of fun.
I recently redid my entire system in my 78 and it functions perfectly and is very cool. To get to this level, I had to disassemble the entire interior and re-seal the whole set of ducts as well as make some ducts where GM fell short (Ther was a 1" gap between my defroster duct on the control unit and the duct in the top of the dash). You wouldn't believe how much air leaks out of this system behind the dash when it is poorly sealed.
Once sealed, the system blew very cold air (and lots of it, no need for a C4 blower motor here).
Remember, these A/C systems were used in GM cars with two and three times the interior space. There should be plenty of cooling power for our small cockpits. Nine times out of Ten, the issue has to be in the delivery mechanism of the cool air.
I'm not saying there isn't room for improvement. The shutoff valve is definitely a weak point for several reasons. The control circuit is weak at best and doesn't really hold the valve shut unless you are in the max cold position, and the fact that it is only in one of the heater core lines is also a problem. Heat from the other line does naturally bleed into the core around the valve. Someone posted a thread where they used a valve from a Ford Explorer (I Think) as a replacement. The Ford valve not only shuts off the water, but redirects it back to the engine through the return line, completely isolating the core. A clever solution which retains the functionality and improves on the system.
Heater cores and vacuum circuits are not as flashy as cam specs and carb jetting, but they are just as challenging and rewarding to get running correctly. I find the challenge of making the old systems work to be a lot of fun.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Originally Posted by SLVRSHRK
I think the stock system is more than adequate when properly refurbished and running correctly. Having said that, it is not an easy task on such old cars.
I recently redid my entire system in my 78 and it functions perfectly and is very cool. To get to this level, I had to disassemble the entire interior and re-seal the whole set of ducts as well as make some ducts where GM fell short (Ther was a 1" gap between my defroster duct on the control unit and the duct in the top of the dash). You wouldn't believe how much air leaks out of this system behind the dash when it is poorly sealed.
Once sealed, the system blew very cold air (and lots of it, no need for a C4 blower motor here).
Remember, these A/C systems were used in GM cars with two and three times the interior space. There should be plenty of cooling power for our small cockpits. Nine times out of Ten, the issue has to be in the delivery mechanism of the cool air.
I'm not saying there isn't room for improvement. The shutoff valve is definitely a weak point for several reasons. The control circuit is weak at best and doesn't really hold the valve shut unless you are in the max cold position, and the fact that it is only in one of the heater core lines is also a problem. Heat from the other line does naturally bleed into the core around the valve. Someone posted a thread where they used a valve from a Ford Explorer (I Think) as a replacement. The Ford valve not only shuts off the water, but redirects it back to the engine through the return line, completely isolating the core. A clever solution which retains the functionality and improves on the system.
Heater cores and vacuum circuits are not as flashy as cam specs and carb jetting, but they are just as challenging and rewarding to get running correctly. I find the challenge of making the old systems work to be a lot of fun.
I recently redid my entire system in my 78 and it functions perfectly and is very cool. To get to this level, I had to disassemble the entire interior and re-seal the whole set of ducts as well as make some ducts where GM fell short (Ther was a 1" gap between my defroster duct on the control unit and the duct in the top of the dash). You wouldn't believe how much air leaks out of this system behind the dash when it is poorly sealed.
Once sealed, the system blew very cold air (and lots of it, no need for a C4 blower motor here).
Remember, these A/C systems were used in GM cars with two and three times the interior space. There should be plenty of cooling power for our small cockpits. Nine times out of Ten, the issue has to be in the delivery mechanism of the cool air.
I'm not saying there isn't room for improvement. The shutoff valve is definitely a weak point for several reasons. The control circuit is weak at best and doesn't really hold the valve shut unless you are in the max cold position, and the fact that it is only in one of the heater core lines is also a problem. Heat from the other line does naturally bleed into the core around the valve. Someone posted a thread where they used a valve from a Ford Explorer (I Think) as a replacement. The Ford valve not only shuts off the water, but redirects it back to the engine through the return line, completely isolating the core. A clever solution which retains the functionality and improves on the system.
Heater cores and vacuum circuits are not as flashy as cam specs and carb jetting, but they are just as challenging and rewarding to get running correctly. I find the challenge of making the old systems work to be a lot of fun.
Advanced
Joined: Jul 2003
Posts: 95
Likes: 1
From: Davenport FL
I have used all three, the shut off valve, the OEM vacuum system, and looping the in/out hoses. IMHO, the OEM looks the best, works the worst. The shut off valve looks the worst, works the best and the hose looping thing is in the middle somewhere. I am not sure if I have ever been in a C3 that would really freeze you, but I always live south of I-10 too
http://www.mycarframes.com.
http://www.mycarframes.com.
Burning Brakes
Joined: Mar 1999
Posts: 1,047
Likes: 3
From: CA
Originally Posted by mirrorfinishman
When the original vacuum operated 'heater control valve' is working correctly, it will only allow hot coolant to to enter the heater core when the function switch is in the postion for heat.
The 'heater control valve' is designed to close off all coolant flow to the heater core when the function switch is in any other position.
That is the way the system was designed and that is the way the system works when everything is functioning correctly.
There is really no need to re-invent anything.
The 'heater control valve' is designed to close off all coolant flow to the heater core when the function switch is in any other position.
That is the way the system was designed and that is the way the system works when everything is functioning correctly.
There is really no need to re-invent anything.
