hybrid system 1980s/1990s questions

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hybrid system 1980s/1990s questions

Postby rustystuff » Mon Mar 11, 2019 7:48 pm

Hi, hoping for some info on how to approach this. I am a newbie to A/C repair but have an idea of how it works. I have a 1981 trans am factory A/C car that has a newer engine and an HD6 A/C compressor installed. Originally had an A6 compressor, and I have read either 3.25 or 3.75 pounds of R12. The system uses a fixed orifice in the evaporator inlet, no POA or TXF valve.
I want to make this system work, so I will be making the needed A/C hoses to connect the compressor to the original system, will replace all orings with the green ones, replace the dryer and fixed orifice, evacuate the system, and charge with R134. I am replacing the compressor cycling switch with one set for R134 pressures.
The trans am system has been discharged for many years. I am hoping the evaporator and condensor do not leak but no idea yet until I can pull a vacuum on the system.
Few questions..I want to replace the fixed orifice, is there a certain one I should buy to work with the R134, or just buy one from a newer car that originally had R134?
If there is any residual R12 oil in the evaporator or condensor will it boil out by pulling the vacuum? The compressor is also used and I would think it also has residual R134 oil in it.
Since I do not know how much R134 to add can I use vent temperature vs ambient temperature and gauge pressure readings to know when the system is full?
Thanks for any help you can give!
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Re: hybrid system 1980s/1990s questions

Postby bohica2xo » Mon Mar 11, 2019 10:16 pm

Some of those cars had A6 compressors, some had R4's. Since they were CCOT already, you just need to connect the new compressor.

Use a new accumulator, they are 134a compatible. Use the OEM size White .072 orifice tube.

The original condenser for that car was a tube & fin. You will probably ne disappointed in the performance with 134a. I would upgrade the condenser to a new parallel flow unit. I know they make one for that car.

Be sure to flush the evaporator thoroughly of it has been sitting open to atmosphere. You need to get all of the old oil out of any component you re-use, because the 134a requires a PAG lubricant.
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Re: hybrid system 1980s/1990s questions

Postby rustystuff » Tue Mar 12, 2019 2:28 am

Thank you! You are right, I double checked and this trans am had the R4 compressor, so I will have to double check the original amount of R12 it used. I will also see about a newer style condenser, as far as performance do you mean vent temperature will not get low enough with the original?

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