A/C advice - convert to R134 or stay with R12 (Page 1/2)
Sledgehammer MAY 30, 05:03 PM
Have an 87Gt which as we all know was born with R12 refrigerant. I am restoring this car, has been in storage for 15-20 years.

There is no r12 refrigerant in the system at this time. Leaked out I’m sure over time and lack of use.

I can check for leaks and recharge with R12 which is expensive to obtain .

Or

I can convert to R134. I have a new accumulator/receiver dryer, and tube to install. I have no knowledge whether compressor is good or bad.

The questions I see are: 1. Refrigerant oil in compressor, but is R12 oil. Do I have to clean old oil out of compressor before adding PAG oil?
2. Is it worth the effort, or replace the compressor and use the PAG oil ( cost for compressor $200 about same for R12
refrigerant.
I am basically asking for a recommendation as to which direction to choose. Any advise gladly accepted.
RWDPLZ MAY 30, 05:57 PM
System is empty, hasn't worked for an indeterminate amount of time, and compressor is likely bad. Replace the compressor with new and convert to R-134A. I would only stay with R-12 at this point if the car is a museum piece or was recently working with R-12 and a minor leak was repaired.
Sledgehammer MAY 30, 07:27 PM
Thank you for our recommendation. I was really unsure whether to go through the process for inputting R12 again and finding a bad compressor after all that expense. I feel replacing the compressor, oil, R134 is more of a sure bet.

I have been looking but can’t find the refrigerant capacity for the system, any idea what the old R12 capacity is? (I can reduce to the 85% for the R134)

Also, the compressor type? This is an 87GT with the 2.8 V6.

The parts houses seem to think theirs (H6 I believes the one)

Thank you

[This message has been edited by Sledgehammer (edited 05-30-2020).]

RWDPLZ MAY 30, 07:47 PM
Original R-12 capacity is 2.5lbs, so yes the R-134A capacity is 80-90% of that, which works out to about 3 12oz cans. Other than the new high and low side adapter fittings, the only other change is adjusting the cycling switch on the accumulator to 21psi instead of the R-12's 25psi.

Oil capacity for R-12 is 8oz of 525 viscosity mineral oil. For an R-134A conversion, it's 8oz of whatever the compressor manufacturer recommends, usually PAG46, but some people swear by Ester oil for conversions.

Original compressor for an 87 GT is either a DA6 or an HR6, the changeover took place around the 1987 model year. Ask for a new compressor, it will have an improved internal design while being externally identical to the DA6/HR6 design (they're indistinguishable externally). The Four Seasons 58255 is a good one.

Here's a list of parts you'll probably need:

http://www.fiero.nl/forum/Forum2/HTML/000652.html
Dennis LaGrua MAY 30, 08:32 PM

quote
Originally posted by RWDPLZ:

Original R-12 capacity is 2.5lbs, so yes the R-134A capacity is 80-90% of that, which works out to about 3 12oz cans. Other than the new high and low side adapter fittings, the only other change is adjusting the cycling switch on the accumulator to 21psi instead of the R-12's 25psi.

Oil capacity for R-12 is 8oz of 525 viscosity mineral oil. For an R-134A conversion, it's 8oz of whatever the compressor manufacturer recommends, usually PAG46, but some people swear by Ester oil for conversions.

Original compressor for an 87 GT is either a DA6 or an HR6, the changeover took place around the 1987 model year. Ask for a new compressor, it will have an improved internal design while being externally identical to the DA6/HR6 design (they're indistinguishable externally). The Four Seasons 58255 is a good one.

Here's a list of parts you'll probably need:

http://www.fiero.nl/forum/Forum2/HTML/000652.html



Good info but PAG oil is recommended for use in only new R-134a installations .Ester oil is what is recommended for R-134a conversions as it will mix with the 525 oil residue . PAG oil does not do this.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

RWDPLZ MAY 30, 08:56 PM

quote
Originally posted by Dennis LaGrua:


Good info but PAG oil is recommended for use in only new R-134a installations .Ester oil is what is recommended for R-134a conversions as it will mix with the 525 oil residue . PAG oil does not do this.




There he is! What took so long?
Sledgehammer MAY 30, 09:07 PM
Thanks again.

I see 3 types of Orfice tubes shown. Which one is recommended Standard, variable, extreme?
Also I understand that one should adjust the low side pressure switch. Is that an arbitrary 1/8-1/4 counter clockwise turn on the adjustment screw or ?

When I purchase the accumulator I also bought an orfice tube. It looks like a “standard”

Everyone agree on “Ester oil” for the retrofit, (8 oz ) In my case the only residue would be in the hoses.

[This message has been edited by Sledgehammer (edited 05-30-2020).]

RWDPLZ MAY 30, 09:58 PM
The more expensive $30 variable ones are made to improve cooling when the car is stopped, like in traffic or just idling. It's meant to more closely mimic the operation of the thermal expansion valve used by most non-GM systems. Standard VS Variable though, nobody seems to agree if it's worth it or not. One thing to consider is it introduces moving parts to what previously was dead simple, introducing a potential failure point.

If you can get good performance from the standard one, I wouldn't bother upgrading. If the standard orifice tube doesn't perform well at idle or in traffic, it may be worth trying to see if conditions improve.

The procedure to adjust the cycling switch is to unplug it, turn the screw clockwise or counterclockwise half a turn, plug the connector back in, and observe the reading on the low side gauge. If it's now above 25, turn the screw the other direction. If it doesn't get down to 21, keep turning until it does. Lower than 21, you went too far. Or just buy the switch pre-calibrated for R-134A @ 21psi.
Sledgehammer MAY 30, 11:02 PM

Great info, thank you .

One last question : There are shrader valves on the service ports, there are shrader valves on the conversion adaptors. Are the existing shrader vale’s on the service ports removed when installing the conversion adaptors?
RWDPLZ MAY 30, 11:42 PM
Yes, you only want one schrader valve per port. Good conversion fittings will have their own valves, like the ones in the parts list. Remove the valve from the Fiero's high side line, and one of the two ports on the accumulator where you will install the conversion fitting. Leave the other valve on the port for the cycling switch. The Fiero's high side schrader valve is larger than the more typical tire-type valve in the other ports, that is what the special valve core tool is for.