Just bought a 1988 GT, V6, 5 speed, 12K miles. Very well maintained car. I am going to have the A/C system checked. Looking at the fittings, it is still R12. If the system doesn't hold vacuum, should I convert to R134? The most recent articles I searched in Pennock's are from 2014. If the conversion is done, can the existing compressor be used? Some have suggested that OEM compressor will work with either freon. Some have suggested replacing the accumulator. Should anything else be replaced? Your thoughts please. Thanks for any experienced input.
The proper R12 to R134a involves evacuating the system of any remaining R-12 and mineral oil, replacing the accumulator, orifice tube and any leaking O rings. Then the system is vacuum pumped to 29in HG and should be held there for 30 minutes. If the vacuum holds then recharging with the proper amount of Ester oil and R-134a can begin. This is the abbreviated procedure. For the detailed charging procedure, there are many You Tube videos on it.
------------------ " 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 "
The 88 GT comes with the better HR6 compressor. At this point however, the compressor and seals are 30+ years old. I would at minimum replace the front shaft seal and switch seals if not the entire compressor. I would also replace all the o-rings except the two at the condenser, unless they are leaking. Accumulator is a must due to the desiccant, and orifice tube is also cheap insurance. Original switches can be reused if the connectors are not broken, or converted over to the newer style.
...You can get R12 on eBay...I changed over to R134 a couple years ago with just evacuating the system and, installing hose adapters, and nothing else. Cooling is adequate, but will be colder with the changes mentioned...Being that I can get R12 now, I'm thinking about going back to it...Colder...
Most reputable sellers will require proof of EPA Section 609 certification in order to purchase R-12, which isn't difficult to get at all. You should still re-seal the entire system if you do go the R-12 route, including the high and low side schrader valves (accumulator will come with a new low side). This would be the way to go if you want to keep that 12k miles car all original looking, and don't mind spending more to do it. This is of course the worst time of the year to buy R-12.
Plus Most selling "R-12" on Ebay and elsewhere are sell crap known as "Freeze-12" and other names containing a mix of refrigerants including Propane, Butane, and others that have problems and Illegal for Vehicle use.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Thanks for all your responses! I will have the system sucked down to check for leaks first. Of course, i don't have that kind of expensive equipment. On a previous 88, when the compressor seized, there was some company that sold a kit to convert to R134, along with a new compressor. I'll have to check my records. I've read several responses on this forum over the years that recommended sticking with R12. I'll balance all my options. First, I have to replace the 32 year old Goodyear Eagle-4's...this Friday! They're not weather-checked, but I don't trust them.
It contains a bag of water/moisture absorbing desiccant. The purpose is to absorb moisture in the system. Once the system has been opened (or just due to age), the desiccant becomes saturated, and the bag containing it may actually rupture and spread throughout the system, as well as no longer absorbing water, that can combine with the hygroscopic refrigerant oil, cause corrosion, freezing in the evaporator or orifice tube, etc.
This is why the accumulator comes with plugs on the inlet and outlet. You want to add oil and install it in the car as the last step before you draw a vacuum on the system to check for leaks and add refrigerant.
Originally posted by sledcaddie: Why is the accumulator a "must"?
OE ones and many aftermarket units are Not compatible w/ R134 and desiccant "bags" can fail then F'ed the whole system.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Thanks Ogre, valuable information. I can get the certification if I decide to go back to R12...And I have 2 good friends in auto repair shops that are certified to use it. They will get it for me...But, as I said, the R134 is adequate, so if it ain't broke, don't fix it...
[This message has been edited by FX (edited 05-28-2020).]
All good brands like 4 seasons, the Accum/drier are built to take R12 and R134 now. Just easier and cheaper for them to have 1 part takes both. ~ 20 years ago, can easily find NOS units only take R12 in many store inventories and many bought them to fix AC. You might still find on Ebay etc but you not want them.
OE ones and many aftermarket units are Not compatible w/ R134 and desiccant "bags" can fail then F'ed the whole system.
Used a standard #33181 Four Seasons R-12 accumulator for my R134a conversion in my 87 GT. It uses the 3800SC GM V7 Compressor. That was 7 years ago and the system is still working great.
------------------ " 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 "
[This message has been edited by Dennis LaGrua (edited 05-29-2020).]
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.
5° - 12°F colder air (at hot idle) Reduced compressor load and extended compressor life Improved performance when converting from R-12 to R-134a Improved city fuel economy & emissions Improved performance in factory R134a systems
How it works
The Smart VOV (variable orifice valve) uses system pressure and refrigerant flow to move a metering piston relative to a fixed opening in the sleeve. The piston movement is resisted by an attached spring.
When idling at high ambient temperatures, the piston shifts to a smaller metering area similar to a TXV. This compensates for the reduced compressor output and increases the cooling performance. The Smart VOV also has a unique re-open feature which reduces compressor pressure for severe idle conditions.
At highway speeds, the Smart VOV operates on a large orifice. The net result is better performance than a TXV without the complexity or reliability concerns.
Unlike a TXV, which has constantly moving parts and small internal clearances, the Smart VOV is stationary during most operating conditions and has large internal clearances. Its low friction floating design insures smooth operation and extremely long life.
