Hi

Posting this mostly to help anyone else who is looking at a thirdgens AC system in the modern era. you'll find a lot of posts here from through the years of people fighting about wether or not it's possible to have a successful r134a system in these cars. I personally think a lot of that is because of the varying ways that people attempt to solve the problems with thirdgen AC, and also the availability of certain new that did not exist when they were posting.

ANYWAY. So on to what worked for me:

The number one most important thing I learned after multiple compressors and charge attempts. The GM R4 compressor, wether reman from any company, or new from GM, is never to be trusted. at this point any R4 compressor you get from anywhere is liable to have been sitting on the parts shelf for years at this point. I personally had 2 new GM genuine R4 compressors blow the case seal within a week of changing.

Enter GPD.....

GPD, makes an R4 sized compressor but what's special about it is that is actually a modern scroll type compressor(like what r134a factory cars have). this GPD compressor is not the one that comes up when you look for parta for these cars on Rock Auto. (Part #7511370). That part is the STANDARD R4 TYPE.

the scroll type is 6511348. This compressor has the correct grooves for our drive belts, but its clutch pulley is slightly larger than the factory pulley.

This requires you to use a slightly longer belt. in the case of my 305 TBI this belt is AC Delco part 6K935.

I then also replaced the condensor with GPD 3231C. This is a parallel flow condenser, which is designed to work efficiently with an r134a system. alot of previous threads where people converted the factory system to 134, they retained the factory tube and fin condenser. That's a huge part of their problems.

I also chose to replace the compressor hoses with GPD 4811708.

From previous forum posts and a YouTube video of a guy with a similar scroll type compressor, I decided to use Motorcraft YG346 RED fixed orifice tube.

I used the GPD drier bottle, part 1411347.

Lastly I used the GPD 4711411 evaporator coil. this is probably the most important part of the puzzle. the factory evaporator has a ton of built on closed cell foam. you can't remove it without it breaking and it also is already shot by the time you get in there. I did not do this originally and I chased 60F vent temps on an otherwise perfectly operating system. The following is the second most important thing I think that I did for the system. I ordered new 3/4" squares of closed cell foam from Amazon and put all around the evaporator coil. The idea is you need to be DANG sure that the air has NO path except through your new evaporator coil. On ALL of these cars, unless you address this, it will be a weak point. look at the below photos:






Seal any box cracks with rtv. And get foam in any path air can bypass the evaporator.

Lastly, my blower label says 2.25 lb of r12. If you convert that to r134, that's about 28-30oz of 134. I don't know why, but there's tons of conflicting information. I found the capacity listed as 3LB of r12. This converts to more like 38-40oz of 134a. This amount was incorrect in my case. I had to remove and recharge with about 30oz when the outside temp hit 100F. that restored full function. Best case scenario you can use a digital machine and load up 28, and do 1 oz at a time while watching gauges on a hot day. But get as close to 30. IMO

Current vent temps at 90f full sun load:





Don't let anyone tell you you can't have an r134a system that performs.

 

Excellent write up, thanks for sharing! I've been thinking about getting my AC fixed up for the last 7 years or so, might finally be time if a recharge doesn't work (my system was retrofitted for R134a before I got the car, but stupid teenage me broke off one of the pressure fitting caps and let most of the refrigerant out back in 2019 ). Anyways, for the compressor, did you have to do any rewiring at the plug/ did the stock brackets work?

 

Unfortunately it looks like the condenser from GPD isn't available right now. Hopefully RockAuto gets it back in stock soon.

 

Thanks for the write-up. Very interesting about the GDP compressor. 1st I've heard of that. - I concur, a 134a conversion, a successful one is possible. Making sure you keep hot air out, and air blowing where it needs to blow. I even managed with all factory parts, none of the modern conveniences...... https://www.thirdgen.org/forums/cool...sion-here.html

 

Compressor is a complete bolt in. Wires plug right in. The only mod was the longer belt to account for the slightly larger clutch pulley !

 

That happened to me too. I setup the notification they have, and it came back within a few weeks.

 

Hey! Nice! we love to see it

 

Did the same. Fingers crossed it doesn't take too long. It's supposed to be 90 here next week. I know that's not crazy for a lot of people, but it's wild to see that in western Washington in June. Not looking forward to the rest of the summer.

 

90 all week here in Socal. extremely excited to have working ac.

 

Good deal! Just bit the bullet, got everything except the evap and hoses. Hoses for the 3.1 aren't available new at the moment, and mine are in pretty good shape. Looking forward to getting that all done next week, wish I woulda done this sooner! Gonna be driving down to North Carolina this weekend, gonna be "fun" having no AC in near 100f humid weather one last miserable drive for posterity!

 

Just realized that you had a V6 as well. Check RockAuto, your condenser is probably gonna be completely different from the OPs, same for the hoses. Our V6s have the AC compressor mounted on the driver's side, not the pass side. Not sure about the 2.8s, but parallel flow condensers for the 3.1 are available and in-stock, and are slightly different from the 305/ 350 condensers (line placement). I ended up ordering a Spectra parallel unit, only $130 after shipping and taxes The hoses in the original post will be far too short for your compressor location, since it's on the other side of the motor. I was not able to find new hoses for the 3.1, 2.8 may be the same, I'm just going to be making very sure that they're all cleaned out. I'll probably have to have a hydraulic shop make a set for me if the stock units don't hold up, only hoses I could find for the V6 cars were used...

I'm also unsure about the belt, but we'll see how everything sizes up when my parts get here. According to RockAuto, the pulley sizes should be exactly the same, but I'm gonna find out how true this is next week when I have my new parts on hand.

 

Interesting, when I check for the 89 2.8, it only shows the OSC one in stock, a tube and fin one.

 

Dang, gotcha, 2.8s musta been slightly different on the condenser vs the 3.1 then. Looking at 'em closely, seems that the 3.1 condenser (SPECTRA PREMIUM 74426) is VERY slightly wider than the 2.8 (SPECTRA PREMIUM 73231), 2mm according to RockAuto. Fittings look to be in the same place, but I can't guarantee that it'll bolt up the same as your stock one.... apparently the outlets are a different size between the two as well, that seems odd. Shame the 2.8 parallel units are out of stock, was hopin I could help you get up and running a little sooner

 

I may just order one anyway. If it's all the same parts, I doubt it will make much difference.

 

I love what you've done both with the text and pics. Forcing ALL the air thru the Evap coil is probably the best advice one could give on this topic. You nailed it.

Mine is a 89 2.8 V6, and I'm hoping the other V6 guys will update this thread with their pics and stories.

Great Thread.

 

I "Know a guy" who buys NOS R12 on Craigslist and runs it in his old cars. In fact, he generally buys in in the winter (when it is cheap) and stores it. I think he buys the correct R12 system lubricant, "Mineral Oil" on Amazon.

He is very pleased with his old car's AC performance!

 

Been waiting for that "guy" to chime in !!!

 

If you wanna gamble wGM R4 compressor seals with 3x $40 cans of r12 that is an option. After the 2nd bad NEW GM genuine, I didn't.

 

Replying to the thread for the friends who have responded (I'm also going to edit above).

Today was 100F. I realized that I was slightly overcharged. It seems there is confusion about wether the correct weight is 2.25lb or 3lb of r12. All this to say: ~30oz of r134a is what's got my vent at 41f at even 100F.