A/C pressure switch adjustment

TBirdDriver

TBirdDriver

Registered User
The A/C in my car has been converted to 134A.
134A is not as efficient as r12.
The pressure switch on the accumulator for our cars are adjustable. If you remove the electrical connector and look down in there, there is a screw that you can turn. Apparently 1/8 of a turn counter clockwise will reduce the pressure by 4 lbs. that the A/C compressor will cycle. (1/8 of a turn clockwise will increase the pressure that the compressor cycles).
I have read that if you convert to 134A from r12, because 134A is not as efficient, you should reduce the pressure that the A/C will cycle. (1/8 turn counter clockwise).
Has anyone done this?
How does reducing the pressure that causes the compressor to cycle help efficiency?
 
TBirdDriver said:
The A/C in my car has been converted to 134A.
134A is not as efficient as r12.
The pressure switch on the accumulator for our cars are adjustable. If you remove the electrical connector and look down in there, there is a screw that you can turn. Apparently 1/8 of a turn counter clockwise will reduce the pressure by 4 lbs. that the A/C compressor will cycle. (1/8 of a turn clockwise will increase the pressure that the compressor cycles).
I have read that if you convert to 134A from r12, because 134A is not as efficient, you should reduce the pressure that the A/C will cycle. (1/8 turn counter clockwise).
Has anyone done this?
How does reducing the pressure that causes the compressor to cycle help efficiency?
Click to expand...
Yes. What you want is the lowest pressure you can get without the evaporator freezing up. Start with about 1/4 turn and see if the air warms up and the airflow seems to drop off. Thats a sign of freeze up. If you turn the A/C off and wait for about 5 minutes and turn it back on and its cold again, then you've confirmed it.
By lowering the cycle pressure, the compressor will run longer. The longer it runs, the more fuel it needs, but you get colder air. In terms of efficiency, I'm not sure theres any real change. The efficiency is helped more by a better condenser which pulls out more heat. :cool:
 
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