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1968 Factory A/C

franklinair

Well-known member
Joined
Mar 1, 2007
Messages
4,741
I'm currently working on a '68 Mustang with factory A/C, looking at how to improve the cooling when using the A/C.
The factory system has one hot water shutoff actuated when A/C is selected.
That leaves the other hot water line still allowing hot water to the heater core. Even if there's no hot water flow it can still allow heat transfer into the heater core.
NPD lists another water valve (P/N 18495-1, $12.95) that can easily be installed on the second hot water hose. I'm going to install it, and connect the same vacuum line that actuates the Factory valve. This will shut off all hot water to the heater core when running the A/C.
When done, I'll shoot a photo to show the installation. (And results)

Neil
 

Ruppstang

Well-known member
Joined
May 22, 2009
Messages
3,032
I'm currently working on a '68 Mustang with factory A/C, looking at how to improve the cooling when using the A/C.
The factory system has one hot water shutoff actuated when A/C is selected.
That leaves the other hot water line still allowing hot water to the heater core. Even if there's no hot water flow it can still allow heat transfer into the heater core.
NPD lists another water valve (P/N 18495-1, $12.95) that can easily be installed on the second hot water hose. I'm going to install it, and connect the same vacuum line that actuates the Factory valve. This will shut off all hot water to the heater core when running the A/C.
When done, I'll shoot a photo to show the installation. (And results)

Neil

That is interesting Neil, I have thought about the second line and the heat transfer.
Once it is done you may have to wear a sweater when the AC is on!
Marty
 

hatchdog

Well-known member
Joined
May 8, 2017
Messages
164
Looking forward to your pictures Neil. I replaced the heater water control valve on my car and it didn't help lower the a/c temp as I hoped. Thus, I have a perfectly good valve on hand and I may do the same as you.

On the subject, would it make sense to install a manual inline shutoff valve to shut off hot water to the heater core in the summer? Would this negatively affect the cooling process if water is not going thru the heater core? And, would this be a problem with the guage sending unit? My car runs very cool according to the guage even with the a/c on while cruising at 70 mph with the outside temp 95*. Just did this last weekend.:grin:
 
OP
OP
franklinair

franklinair

Well-known member
Joined
Mar 1, 2007
Messages
4,741
hatchdog:
Your car is what made me start thinking of this mod. When I re-did the A/C, the gauges had perfect readings, indicating that all the A/C system components were operating correctly.
The shutoff valve you mention would have no ill effect on the engine cooling system, and the temp gauge sensor (on the intake manifold) will still read correctly. (IIRC, I installed a 160 degree thermostat which is why the temp gauge reads 'cool'. And the radiator cap with the thermometer should confirm the temp reading.)
When I lived in Miami (95 degrees/90% humidity) I had that A/C so optimized it blew out 40 degree air. (On the highway, constant higher RPM, the evaporator would ice up after about 30 minutes obstructing the airflow. :eek: Then I had to use recirc/fresh air to melt the ice.)

Neil
 

p51

Well-known member
Joined
Aug 2, 2005
Messages
1,025
Location
NorCal
I'm currently working on a '68 Mustang with factory A/C, looking at how to improve the cooling when using the A/C.
The factory system has one hot water shutoff actuated when A/C is selected.
That leaves the other hot water line still allowing hot water to the heater core. Even if there's no hot water flow it can still allow heat transfer into the heater core.
NPD lists another water valve (P/N 18495-1, $12.95) that can easily be installed on the second hot water hose. I'm going to install it, and connect the same vacuum line that actuates the Factory valve. This will shut off all hot water to the heater core when running the A/C.
When done, I'll shoot a photo to show the installation. (And results)

Neil

What a cool idea!... literally :wink:
 
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