hybrid system 1980s/1990s questions

[rustystuff]

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!

[bohica2xo]

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.

[rustystuff]

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?

[rustystuff]

couple more questions if I could. I decided to go with all new 1995 z28 parts, so new compressor, condenser, accumulator, orifice tube, and hoses, all for R134. Only used part from the 78 trans am will be the evaporator. So the oil charge and refrigerant charge I will use the 95 z28 amounts.
Does it matter what side of the condenser the compressor discharge line connects to? top or bottom or doesnt matter?
The liquid line coming out of the condenser to the evaporator was originally an aluminum tube, can I replace this with a custom hose or is there a reason for using the tubing instead of hose?'
Thanks!

[Tim]

couple more questions if I could. I decided to go with all new 1995 z28 parts, so new compressor, condenser, accumulator, orifice tube, and hoses, all for R134. Only used part from the 78 trans am will be the evaporator. So the oil charge and refrigerant charge I will use the 95 z28 amounts.
Does it matter what side of the condenser the compressor discharge line connects to? top or bottom or doesnt matter?
The liquid line coming out of the condenser to the evaporator was originally an aluminum tube, can I replace this with a custom hose or is there a reason for using the tubing instead of hose?'
Thanks!

Condenser. I will not matter which side the connections come out on, drive or passenger. But the larder connection discharge has to be on top.

[rustystuff]

Thanks, I did not describe the condenser well enough. Both ports are on the passenger side. Is there a reason the compressor should discharge into the upper part of the condenser? Looks like this one was backwards. After reviewing the layout of the 95 Z28 flow it looks like the compressor discharge will connect to the bottom of the condenser, and the top will exit to the fixed orifice at the input of the evaporator. The larger connection is on the bottom.
The z28 had a TXV valve, so on the 95 Z28 the upper line of the condenser went to a dryer and then to the TXV, but since I have a fixed orifice and no TXV the upper condenser line will now go to the fixed orifice at the evaporator input and the output of the evaporator will go to an accumulator and then back to the compressor.

So last question, does the liquid line from the upper outlet on the condenser to the fixed orifice have to be an aluminum line or can I make a hose for it instead? I think it will be a #6 hose.

[Tim]

As you can see in this link. I fitting of the condenser is on the passenger side and the discharge is on top. This matches the hose set coming from the compressor.

http://www.ackits.com/index.php?route=p ... arch=G4393

[rustystuff]

That picture is actually upside down, the male threaded fitting is on the passenger side bottom, so the compressor discharge will connect to the bottom.

[Tim]

Did some research and this condenser is designed for a reverse flow cooling system. Like the 95 Camaro used. If you have a standard flow you're going to have hot on the bottom from the condenser and hot on the top from the radiator. Also, the Camaro had a low mount compressor. Another reason they used that condenser. Might not be the best choice for a condenser.

[rustystuff]

I have a 1995 Z28 engine in the 78 trans am, so I have the low mount 95 compressor and condenser from the Z28, and the reverse cooled engine as well. I am making custom lines. Difference is instead of running a TXV valve like the 95 Z28 did I am using a fixed orifice in the 78 trans am evaporator. So where the upper condenser line used to go to a dryer and then the TXV it will now go directly to the 78 evaporator, then out of the evaporator to the 78 accumulator, and then back to the 95 compressor. Sound like it will work?