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Discussion Starter · #1 ·
Hello,
I change the R12 to R134a and we filled up with 500g R143a. Fan is runnig and AC compressor too. The air inside cab is not really cool. The pressures on Hight pressure line and low pressure line seems be okay. See attached pictures, they explain the actual situation. Have anybody an idea why the air is not cold enough? Thanks

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If the pipe is frozen like in the picture explains why its not cold due to refrigerant it not able to pass. Before the expansion vale should be hot and after the expansion valve should be cold but you may have another restriction where its cold/frozen. Can you share what parts you changed to go from R12 to R134a?

Thanks
 

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Discussion Starter · #5 ·
If the pipe is frozen like in the picture explains why its not cold due to refrigerant it not able to pass. Before the expansion vale should be hot and after the expansion valve should be cold but you may have another restriction where its cold/frozen. Can you share what parts you changed to go from R12 to R134a?

Thanks
Only change the adapters, because the system was nearly one year under nitrogen...Maybe the expansation valve is fault?
 

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1,021 grams

28.37 grams per ounce. X 12 ounces. X 3 cans.
 

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Please understand - your original condensor is optimized for R12 refrigerant. The R134A refrigerant performs best with a modern "parallel flow" condensor to more efficiently remove heat at the condensor.

Your expansion valve system (suction throttling or pilot operated absolute, not sure) is also optimized for R12 - some adjustment required for best operation with R134A.

The old compressor oil for R12 needs to be removed so that an oil that is compatible with R134A can be added. Typically, a liquid flush of the system is required to remove all traces of the old oil.

The R134A molecules are smaller than the R12 refrigerant molecules which allows for too much leakage through the old hoses. Modern "barrier hoses" are required to slow down leakage of the small R134A molecules.

Did you vacuum down your system to remove all air and moisture?

Did you replace the receiver drier or at least replace the dessicant bag in the accumulator, if equipped?

Rick
 

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Discussion Starter · #15 ·
Please understand - your original condensor is optimized for R12 refrigerant. The R134A refrigerant performs best with a modern "parallel flow" condensor to more efficiently remove heat at the condensor.

Your expansion valve system (suction throttling or pilot operated absolute, not sure) is also optimized for R12 - some adjustment required for best operation with R134A.

The old compressor oil for R12 needs to be removed so that an oil that is compatible with R134A can be added. Typically, a liquid flush of the system is required to remove all traces of the old oil.

The R134A molecules are smaller than the R12 refrigerant molecules which allows for too much leakage through the old hoses. Modern "barrier hoses" are required to slow down leakage of the small R134A molecules.

Did you vacuum down your system to remove all air and moisture?

Did you replace the receiver drier or at least replace the dessicant bag in the accumulator, if equipped?

Rick
Did you vacuum down your system to remove all air and moisture? Yes we have

Did you replace the receiver drier or at least replace the dessicant bag in the accumulator, if equipped? Yes,the dryer is new
 

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If the old oil is exposed to air - it'll be "tarr ry" - and reduce heat transfer of evap.
Even tho it hydro'd fine, I had to change the evaporator coil and all is much better
Initially had a new sanden comp and a new condenser - evap can be changed on a big block without yanking engine
 

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500g is hardly enough for your system, that's roughly 18ozs. System with STV should hold at least 3.25 of R12, subtract 20% for 134a as a start. STV systems will freeze the STV outlet when low.
What are your pressures and ambient temp?

Hello,
I change the R12 to R134a and we filled up with 500g R143a. Fan is runnig and AC compressor too. The air inside cab is not really cool. The pressures on Hight pressure line and low pressure line seems be okay. See attached pictures, they explain the actual situation. Have anybody an idea why the air is not cold enough? Thanks

View attachment 148291

View attachment 148292
 
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