Engine Size: 455
Refrigerant Type: envirosafe R12
Ambient Temp: 90
Pressure Low: 30
Pressure High: 200
Country of Origin: United States
Just completed restoration of my AC (A6 compressor). my readings are 30 low 200 high @1500rpm but the vent temps are 50-60. It will go down to 43 vent temp at highway speeds.
What would be causing the high vent temps??
Not using R-12. The pressure-temperature characteristics of Envirosafe are actually considerably different than R-12. POA systems are closely tuned for the design refrigerant.
Like mk378 says-not r-12. Those engineers knew what they were doing when they put that system together for r-12. Anyway---43 at cruise shows that it can cool. Dropping to low speed with climbing vent temps is a classic sign of poor air flow over your condenser. Change your fan clutch to a high quality unit, it is worn out if over 2 years old-yes, all here give that hard working fan clutch that short of useful life. Make sure your fan shroud(I hope it's on the car!) is tight around the edges. Tape it or seal it with some kind of caulk, available at an A/C or plumbing supply. Clean all debris from the front of the condenser. If you have room in front of the condenser, and those older ones had gobs of room, think about putting the largest electric "pusher" fan as close to the condenser as possible, and for simplicity, a driver controlled switch. I like using those modern 30 amp relays, jump the "hot" side for the fan from your horn relay across this smaller relay, which connects straight from the battery, run a 25-30 amp fuse in line for protection. Power this relay by jumping off your "only hot with key on" wire from your windshield wiper. Run the ground wire through your rubber seal around your steering column(no holes to drill) and use a switch from any good auto parts store that turns on with a red glow when in use. Mount it low in front by the column so no holes show if removed later. Hope this helps.
I have ordered a HD fan clutch as the engine temps get high at reduced speeds and stopped in traffic only with the AC on. I have installed a small pusher fan and a driver controlled switch.
Are the pressures OK for my application?
Engine overheating (due to lack of airflow not some other problem) means that your fan is way inadequate for good A/C. So definitely the fan clutch should help. It takes a lot more air for A/C than what is necessary just to cool the radiator.
As far as pressures, who knows with HC.
If mk378 will forgive me, "HC" is the mix you have in there now, which will give goofy readings compared to pure r-12. Again to repeat, you have 43 degrees at cruise, so you are in a good cooling range. Let us know your progress, OK?
Hooked up my gages tonight and the low side was 28-32 but the high was only 125 with 83 outside temps and 50 vent temps.
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