A/C Compressor Hard Line Compatibility

[jmgtp]

I have a 91 Grand Prix with a dead a/c system.

The car has an 05 3500 LX9, and I modded a beretta a/c bracket to bolt to it so that I could use my r12 compressor. All for nothing since the system has lost its charge. It worked before the swap but is dead now. I jumped it at the relay to force the compressor on and it did not provide any cooled air - so that verifies that the system is discharged rather than having an electrical fault.

I believe any late model 3x00 compressor will bolt right to the LX9 block and I can ditch the beretta bracket all together. Getting a 3x00 compressor is the easy part.

Question is, will the 2 existing hardlines that are bolted up to my r12 compressor transfer right over to the r134a 3x00 compressor? Can it be THAT easy? Then a simple evacuation and charge and I'd be good to go, cold air and all (and right now most importantly good defrosting!). What about the a/c clutch, by some miracle is the electrical connection the same between the new and old compressor?

I know most people change the accumulator and dryer as well. Honestly what is the difference between those parts? I don't know much about a/c. I believe one of them is the large cylindrical piece, what is the other part? What happens if I don't bother changing them?

edit: I see that a new accumulator (Autozone) for the 91 system is only $20ish, so no reason not to change it. When I tryed to look up "dryer" it came to the same part. Are they one in the same? And just what does that part do? It seems just like an expansion area?

[WrathOfSocrus]

The location of the ports on the newer compressors are 90* away from the location on the older compressors. You might be able to use the newer line and make the connections at the other end assuming they are the same. I couldn't easily locate good pictures to see if that would work out or not, I'm sure a good hunt online or find a vehicle to inspect like at a junk yard would let you see what models have what and if it would work.

The accumulator and dryer do come up as the same part. I know moisture is the death of an A/C system and they pull vacuum to evacuate any moisture laden air from the system when doing repairs. I believe the dryer aspect of the part uses some hydroscopic medium to pull residual moisture from the system. The accumulator is like u described, sort of a reservoir to reduce fluctuations for constant output.

I have been interested in doing some A/C work since I live in Florida and know lots of people who would love to have A/C running again. While I will be totally honest that I don't know precisely how to locate it in order to replace it, I have been told the orifice tube can clog, particularly if the system has leaked refrigerant and has air (moisture) in the system. The part is cheap and probably worth replacing if you can get at it. The guys on W-body would probably have the info you need there.

You may also be interested in looking at alternative refrigerants and using your current setup. I forget where I heard about it but there are a few companies and the one I remembered off the top of my head - here - has an R-12 replacement. If your compressor is still good or if you can source a good replacement then it might be easier to reuse what you have. Especially with the 3500, as the 3100/3400 have a different lower mounting boss on the oil pan. As long as the current setup works you only need two things - Fix whatever leaked in the first place then get the system recharged.

Another thing that is noteworthy is apparently they are phasing out some refrigerants next year including R-134a. Retrofitting to that just as it is about to go out of 'style' will probably end up costly if the system needs service down the road.

Edit - http://www.familycar.com/ac1.htm Here is a good overview of the A/C system to give you an idea of what does what and where it goes. I would definitely look into replacing any seals or O-rings before getting the system charged.

[jmgtp]

I know there is stuff like Freeze12 but it is somewhat costly and still requires a conversion of fittings. Fact is that r134a (even if phased out next year) would still be available for a long time. Plus I don't want to take my chances on repairing a system with a 20 year old compressor.

Are you saying the LX9 doesnt use the same a/c compressor as a 3x00? I know it has the 2 threaded holes in the block for the compressor and I believe there is a 3rd bolt hole that located on the bottom of the compressor. I don't remember if the LX9 has the accomodations for that.

I believe the hard lines in the back of the '91s r12 compressor have rubber segments as well, meaning I think they could make the 90 degree bend. Even if they could, I don't know if the fittings are the same. Guess the best soluton would be to see if the hard lines from a 3x00 would work with the rest of the '91s hardware.

[WrathOfSocrus]

The link I included above has pretty competitive pricing to it. They even have recharge kits and they say there is no retrofitting needed. Although if the compressor is shot then it probably isn't worth bothering with the older setup.

The LX9 has a different mounting point for the lower bolt on the oil pan. I forget exactly how much it is off by. It isn't much but enough to not work. Most people have been using just the upper two bolts. In my case I also had an engine to trans bracket on a 4T65 that was different than the 4T60 and used a mounting boss on the pan that also changed location. So I modified the 3400 pan to clear the connecting rod bolts and used that.

I've been looking at the different compressors and apparently they had a couple different styles depending on the year and car body. I just came across the compressor for a 3.4 (searched a 96 3.4 on rock auto) and it looks exactly like the older R12 W body compressor. Comparing the compressor from my 89 Cutlass (R12) to the one from my friends 95 S-10 (R134a) the connection looks the same. So your chances are pretty good it will hook up to your lines. If your current setup for mounting your compressor is solid then that might be the best way to go.

The other good option is one for the LX9. It would obviously bolt on directly to the block and pan, and has the same kind of connection for the lines on the side like the gen 2 W body. I see dozens of LX9 compressors on car-part locally in the $40-$75 range, so it should be easy enough to locate one. Then you can either use your current lines or get the Gen2 W body lines to connect it to the system.

[jmgtp]

My current setup is using a modified accessory bracket off a GenII 60v6 (I believe from a W car since it has the dogone bolts to it at the top). I had to cut/grind to get it to work and its held securely but only by 3 bolts. The compressor bolts to 'C' shaped flange in that bracket. It was a HUGE pain to line that thing up, it was like the compressor was a hair to big to fit in the bracket and every bolt hole was a millimeter off. I think I fought it for hours and angels sang when it finally lined up. So between the jostling the compressor took during the swap, its age (20yrs) and the hassle of conversion if I decide I want to go for it I wan't a newer r134a compressor.

I see 2 options as far as compressors - get one off an LX9 motor and have a guaranteed fit or get one off a 3x00 and use 2 bolts at the top. I'd like the LX9 one so it bolts up perfect but depending on what I can get a 3x00 one for I'll go with that.

I think I'm going to start gathering the parts to make it happen as part my winter plans. I'm daily driving the car now and in the morning not having a/c makes defrosting the windshield near impossible, not to mention come next summer I will swelter without it!

I also looked up the orifice tube on the car part websites. You're right, its dirt cheap, like $3. Damned if I know where it goes or what it does!

[WrathOfSocrus]

The orifice tube takes the refrigerant from the high pressure side and forces it through a small opening. When it comes out the other side and goes to an area of larger volume/lower pressure (evaporator) the sudden loss of pressure causes a drop in temperature. Kind of like when you open up the valve on an air tank and it gets cold and can even ice up. A search on w body says it is under the brake booster in the larger of the 2 lines. Because of the small orifice, any debris can clog it and stop the cooling process.

[jmgtp]

Ah, now it makes sense.

I think all said and done I can have working a/c with a genuine r134a compressor for less than $150.

LX9 a/c compressor, scrapyard: $75
Acuumulator/Dryer, Autozone: $20
Orifice Tube, Autozone: $3
Fitting Conversion kit & Refrigerant/oil. Autozone: $30
System evacuation tool, Harbor Freight: $15

Total: $143

I might possibly need new A/C lines for 3x00/R134a compressor, Autozone: $60

[60dgrzbelow0]

I know this is a late entry on the topic...but...this information might also help you from a procedural standpoint on this repair:

http://60degreev6.com/content.php/138-Air-Conditioning-System-Replacement-Tips

[NateD4]

If doing R134 conversions (or repairing a bad A/C system) make sure the evaporator and condensor are new or very clean. Also consider putting screens on the inlet and outlet of the compressor (they are available aftermarket). Also don't use parts store brand or rebuilt compressors (I've never had one last more than a year). The last system I did used a Denso compressor (brand new). No problems with it...

[Joseph Upson]

System evacuation tool, Harbor Freight: $15

Don't you dare, search for a 20% off coupon in one of the automotive magazines and buy the electric vacuum pump for this process. It may still be on sale. Better yet, rent one from Autozone. I have not read where that air operated vacuum pump that I'm sure you are thinking of pulls a deep enough vacuum relative to what you should for an A/C recharge although it will work.