Let's be honest. The real reason R-12 was 'outlawed' was the Dupont patent on R12 refrigerant was to expire in 1996. DuPont actually lobbied the EPA to switch to a 'safer' alternative (R134a) that they held the patent to.

Interestingly, Dupont admin issued a memo in 1996 that directed the production of 750 million TONS of R12 for "tax purposes" before ceasing production. R-12 is still in production in other countries.

In fact, the European Union is investigating Honeywell and DuPont because they also hold the exclusive physical and intellectual patent rights to the new HO1234yf refrigerant.

Can't patent propane - which is good enough for me!

And the only reason you can't legally vent R134a (from a refrigeration system) is the refrigeration lobby.

This is true...

I would like to see high/low side pressures/vent temps at idle and 2000 rpm...

As with any refrigerant, I charge with 75% of the system's rated capacity and check vent temps with a dyno fan on the condensor (to mimic road speed) and I charge for vent temps and pressures, FWIW

My W116 with 9 blade fan and correctly functioning electric (supplemental) fan will knock our 32°F in the vent at 70 mph at 105°F ambient 25% humidity and 48°-52°F in the vents at idle in the drive through with a non worn-out fan clutch.

The 2000 Ford truck I recently did with R-134a ran a very cold 27°F in the vent @ 2000 rpm in 100°F ambient 25% humidity, but that was with a custom sized orifice tube (.052") and compressor cyclic rates with an 11 blade engine driven fan.

Note - Ford's have huge evaporators and condensors, when compared to other vehicles, so this kind of A/C performance is hard to mimic on non-Fords.

My 2001 Mustang is a stock R-134a system running a custom .049" orifice tube and revised compressor cyclic rates. It yields vent temps that will dip to 25°F on the road and 37°F at idle on a 105°F 30% humidity day.

IIRC, A/C pressures dip to 22-24 psi (low) and rise to 310-315 psi (Hi) on the Mustang.

I never see over 340-345 psi on a properly functioning R134 system with adequate airflow...

How can a vehicle have a 27F evaporator temperature??? In humid conditions it will freeze up, and even if the compressor cycles, operate long enough and this will occur.

Seems to me that euro cars are known for fairly weak AC.

What propane are people using, and why arent you mixing it with butane?

Also, it appears that there can be runaway pressures on the high side running straight propane, which is partially why they often say NOT to charge it under vacuum.

There is a lot of risk and lack of straight know-how out there for HC refrigerants, though the whole flammability thing is IMO overblown.

Two quick questions:

-is it bad to use the same gauges for 134a and R12?
-if going to HC, would you use separate gauges for that?
-If youre running a blend, how do you know when one of the two constituents has diffused out?

Not really a problem in California. It's a big problem in Miami Beach. We held evap temps to 33°F-34°F religiously because of the high humidity.

A lot has to do with the fin width in the evaporator too.

Have you ever measured vent grille temps??? they are often 5-10° lower than vent air temps. Our F150 has 17° vent grille surface temps with 25°F to 27°F in the vents....

How do you measure surface temps? I usually just stick a thermocouple down the vent.

I just ordered up some ES12 to try in my SDL.. $30 in gas. I'll report how it does.

-J

A thermocouple is correct for air temps, and we use a infra-red for surface temps.

If you read the East Indian A/C test, it will be a real eye opener....

A thermocouple is correct for air temps, and we use a infra-red for surface temps.

If you read the East Indian A/C test, it will be a real eye opener....

http://www.peachparts.com/shopforum/diesel-discussion/340706-c-vent-temperature-test.html