What pressure?
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Senior User
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From: Gilbert, Arizona (Phoenix
What pressure?
I have a 76 F150 that has been converted to 134A refrigerant. It has a rotary compressor, new filter/drier, new hoses and I just put an electric fan in front of the condenser. Still only blowing 80 degrees F as I go down the freeway. And it's hot outside! 110 here in Phoenix.
How/where would I find out what the correct pressures on the high/low side should be?
How/where would I find out what the correct pressures on the high/low side should be?
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Senior User
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From: Gilbert, Arizona (Phoenix
Thanks. I've got a problem. Low was 70 and high was off the scale. I brought the pressures down to 275 and 45, but temp went up to 100 degrees. Think there might be air in the system but I'm not sure.
Lead Driver
Joined: Jun 2004
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From: Amarillo, TEXAS!
It was definitely overcharged, but it should have gotten colder after venting some refrigerant. Did you change the orifice tube, and did you evacuate the system after changing parts and before charging?
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From: Gilbert, Arizona (Phoenix
This truck has the expansion valve, not the orifice tube (right?). My understanding was that if there is an expansion valve, there is no orifice tube. Anyway, my understanding was it was all done before I purchased the truck. However, when I got the truck, the system was empty. I replaced the drier and the hoses, put a vacuum on the system for 30 mins, then charged with 134A.
Obviously, I put too much in. It was my first time.
However, now that the pressures are more in line, I'm thinking it should be cold.
I'm thinking next thing to do would be evacuate, replace expansion valve, vacuum down, then recharge. Whadda ya think?
Obviously, I put too much in. It was my first time.
However, now that the pressures are more in line, I'm thinking it should be cold.
I'm thinking next thing to do would be evacuate, replace expansion valve, vacuum down, then recharge. Whadda ya think?
Lead Driver
Joined: Jun 2004
Posts: 6,361
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From: Amarillo, TEXAS!
Yes.... Correct (as far as I know). When you got the truck, had it already been charged at some point with R134, or was it just an empty R12 system? If it hadn't been previously converted, did you flush the system with a solvent (such as mineral spirits) and add PAG oil to it, or just add refrigerant? The ester oils used with R12 aren't carried well at all by R134, and aren't compatible with the PAG oils.
When you evacuated the system, were you able to get at least 25 inches of vacuum?
I must be missing something here, because the pressures you are running should have the evap coil at about 50 F. Is the compressor cycling a lot?
When you evacuated the system, were you able to get at least 25 inches of vacuum?
I must be missing something here, because the pressures you are running should have the evap coil at about 50 F. Is the compressor cycling a lot?
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Senior User
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From: Gilbert, Arizona (Phoenix
I'm not sure if it had been charged with 134, I assumed it had been. I did flush system and added PAG oil. I honestly don't remember the amount of vacuum. Regarding the compressor cycling, as far as I can tell, it is always on. I don't hear/feel the clutch kicking in/out at all.
Thanks for the help.
Thanks for the help.
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