Date: Thu, 12 Mar 1998
From: Cary Foster {[email protected]}
Subject: FW: HVAC Fans
Sender: [email protected]

Your expansion valve is probably the culprit. The expansion valve has a 
temperature sensor probe that either fits into the fins of the evaporator 
inside your dash or on the pipe fitting going to the evaporator. A function of 
the valve is to monitor evaporator temperature and adjust the system to keep 
the evaporator from freezing. Sometimes on an old system the dryer (at the 
back of the car) gives up and sends dessicant up to the expansion valve and 
clogs it. 

I recently overhauled my AC system. My system works so well that I have to 
keep the fan on low and turn down the thermostatic switch to about half to 
keep from freezing my face. I put Halls new 3 speed dash fan in, new expansion 
valve, new hoses, rotary pump, larger condensor core in the back and a modern 
high flow fan at the condensor and I run R-12 freon. One other thing I did was 
remove the heater core. Since I live in california, all I do is roll up the 
windows to warm up the passenger compartment. The heater core sits in front of 
the evaporator in the dash. The fan has to blow air thru 4 or 5 inches of 
evaporator core and heater core. Their is so much back pressure here, no air 
gets out.I have driven this car to Vegas in 106 deg temperatures and was as 
comfortable as a modern AC system. 

To properly charge a system you must pull a vacuum of 30psi on the system with 
a vacuum pump for about 2 hours. This will boil off any moisture that has 
collected in the system. Then shut the pump off and watch your gauges for a 
couple of hours. Your low pressure gauge should not budge from a vacuum 
reading of 30psi. If it does, you have a leak.So don't bother wasting your 
$20/lb freon. 

I also changed the thermostatic rotary switch on the dash. I used a later 
model Pantera switch(from Hall) which I wired to turn on the the low speed 
passenger compartment fan, engage the compressor clutch and turn on the 
condensor fan. You never want to engage the compressor clutch without turning 
on the condensor fan. this will build up high pressure in the system and blow 
your hoses. Incidently, you want to buy a compressor that has a high pressure 
relief valve. If your condensor fan quits, the compressor will bleed off the 
high pressure before blowing your hoses. 

I adapted a 10in high speed pancake fan to the condensor fan box without 
cutting anything. This fan pulls air from the outside into the trunk. The 
purpose of this fan is to remove heat from the freon liquid at this point and 
transform the liquid to a gas again (I might have this mixed up). If you are 
using a stock Pantera fan this transformation of the Freon liquid to gas is 
not very efficient because of the poor performance of that fan out of a 
O'keefe and Merrit stove. A high speed fan is just added insurance and they 
don't cost very much. When adding the freon, you want to make sure you have 
low pressure and high pressure gauges hooked up. These gauges will tell you 
when the system is full of freon, if the expansion valve and compressor are 
working correctly and their are no leaks. The low pressure gauge should read 
around 30 psi and the high pressure gauge should read around 175 psi My system 
holds just under 3 lbs of freon. More freon than that will drive the high 
pressure side of the system way above 175 psi and then your hose's blow or 
your high pressure valve at the pump bleeds off $20/lb of Freon. I used a 30lb 
freon bottle and place it on a scale.Once I determined that the system would 
hold a 30 psi vacuum for 2 hours, I opened the valve to the freon bottle to 
let the freon in with the engine running at high idle and AC on full. You have 
to be carefull here, the system will pull 5 lbs of freon in nothing flat this 
way. I think it only took about 2 minutes to fill the system. 

I still prefer to have the condensor in the back. Putting another obstruction 
in front of the radiator just doesn't make sense if you live in hot climates 
with a radiator system that is already inefficient. 

R-134 freon is not as effecient as R-12 freon. These systems I think run 
around 300 psi on the high side. This requires much better hoses with o'rings 
at all the connections. The hoses have to be a special barrier hose. I think 
because freon -R-134 has much smaller moleculer structure and can leak thru 
common R-12 hosing. But you can go down to PeP Boys and buy Freon R-134 and 
fill-er-up just like the old days. 


Date: Tue, 10 Mar 1998 03:00:27 +0000
From: JDeRyke {[email protected]}
Subject: Re:  Just ask Jack
To: Multiple recipients of list {[email protected]}

I'm the last guy to ask about air conditioning, since after all my troubles, 
I've still never gotten across the Mojave with it blowing cold air! I'm the 
one that found the plugged filter screen in the expansion valve assembly too 
late to save a high-pressure hose, and the fact that Toyota and RX-7 junkyard 
rotary A/C compressors drop into the Pantera A/C mount with a little adapter 
and even fit the OEM hoses. I also was convinced by a friend that as long as 
you knew where the 3 tiny screws are that hold the heater blower into the dash 
unit, you CAN actually R & R it without pulling the dash. This is of course as 
long as you don't count skin & blood loss as important... but I did get the 
thing out and a new one back in! J DeRyke