Need help with A/C system after engine swap.

[85 Cutlass Brougham]

I have an 85 Cutlass Supreme Brougham that I swapped a Chevy 350 into in place of the original 231 V6. Now I did the swap about 8 or 9 years and 45k miles ago but never finished setting up the A/C system. I have the V6 compressor bolted to the engine using factory 305 brackets from a 84 HO 305 Z-28. I also swapped in the engine harness from a 85 305 Grand Prix at the time of the swap so that it would look and work like it was a factory set up. I have a new drier, O rings, the Camaro hoses ( necessary for the dual snorkel setup) which I am having lengthened, and a late 70's Q-Jet that takes the 80's A/C idle solenoid. However, I am unsure if this engine is supposed to have orifice tubes or if it takes an expansion valve instead. Another thing is, I don't know if the A/C will run with the computer eliminated. I think it will but have never tried it before. The compressor still spins freely, but I don't know how to drain the old oil which is incompatible with the R134a conversion.I also don't know how much refrigerant it should have after conversion. I am also curious if anyone offers reproduction stickers for the compressor and firewall "suitcase" as I am trying to make it look nice and stock under the hood. Any help would be appreciated.

 

[Uncletruck]

As long as your refrigerant charge is OK, the A/C will or can be made to run without the computer in place, easily. But..... you can't run the original '85 compressor with R134A, it will seize. But... there are new R12 subsitutes on the market now that will allow the old compressors to work as long as the system is filled with only the substitute and the proper charge of ester oil. Unfortunately... you have had the system open for so long, the original compressor is a garbage canner. Take it off, and toss it out. I would recommend completely converting to a full modern 134A system at this point, or you'll be wasting time and money.

-Mark-

 

[joe_padavano]

First, the A/C will not function without the computer unless you make some wiring mods. The computer controls the ground for the compressor clutch relay, shutting it off if there's low freon pressure or if the RPM is too low. You can bypass this easily and still retain the low freon safety switch by connecting two wires in the C1 computer connector. The brown wire in position 19 in that connector is the relay ground. The black wire in position 15 is a switched ground that goes through the low press switch. Connect these two and everything should work (assuming you have freon pressure). You can also connect the brown wire directly to ground, but that bypasses the safety switch and can burn up the compressor if the freon is low.

As for the R134, I changed over my 86 (which was empty) by just filling it with an R134 kit. The system has been working fine for the last year.

 

[dougfather]

I want to consider going to a Vintage Air system. There is a thread somewhere on this site that has a link to a Pontiac 2+2 getting one of these systems. They sell complete set ups with compressor, condensor, evap, and the whole vent control unit. My vents don't work well and the controller has a vacuum leak in it. Vintage Air has electric servos.

I am doing the same engine swap as well. My system was leaking somewhere.

 

[Uncletruck]

I talked with a fellow automotive A/C specialist today about safe ways to keep a stock look by using the old R12 compressor with 134A. He still recommended an R134A compressor as the best long term bet. But, he said with the installation of an inline filter and high pressure relief switch, a good condition R12 compressor can be used with R134A. He said R134A develops much higher head pressure than R12, and the switch will protect it from the overload. He said it is very important to evacuate all the old oil used with the R12 from the system with a vacuum pump, and to install a receiver/dryer with a desiccant made for R134A.
-Mark-

 

[85 Cutlass Brougham]

Where can I find the switch and a dryer for R134a? I really want to keep the stock compressor because I like having almost everything under the hood look like GM put it there, even if they didn't. ( I just finished de-blinging the engine and painted the chrome Holley fuel pump and timing tab black to blend in) Plus, I feel that factory parts combinations tend to be the most reliable for the 20-50k miles year I drive ( mostly in my 260k mile Nissan truck, but the Cutlass is my backup) and I like being able to buy almost everything at the local parts store instead of aftermarket. Oh, also where are the orifice tubes? In the condenser? Or does it use an expansion valve? I have a new dryer, but how can I tell if it is for R12 or R134a? It has been sitting sealed in the box for 9 years so it may be for R12...I dunno. Finally, does anyone reproduce the underhood stickers for the A/C system and the emissions label for the fan shroud? I need them for a 305 Monte Carlo, not a Cutlass. Thanks once again everybody for all your help!

 

[Uncletruck]

Check out this place, lots of great info for a/c parts, retrofits, and conversions:

http://www.autoacrepairs.com
-Mark-

 

[Alanco]

AC revival:

I have done many R134 conversions. First of all, your '85 did not have an old A4 compressor, it is the shorter fatter A6. All that is necessary to make the compressor work (does not matter how long it was not used) is to flush it thoroughly with the new esther oil. You also have to use air to flush your condenser, and the evaporator. The only new part I would buy would be the expansion cannister. This is a flooded evaporator system with a fixed orifice.There is no receiver dryer or expansion valve used. The orifice system can flood the evaporator with liquid refrigerant and since liquid can come out of the evaporator, the liquid goes into the cannister and the engine heat turns it into gas for return to the compressor.

R134 does not have more head pressure than r12. It does have a lower boiling point and the low pressure must be as low as 10-11 psi or it will not be cool. The G-body systems use between 2 and 3 lbs. The way you know when you have enough, is when the low side is 10-15 lbs and the high side will be around 170- 230 depending on the air flow through the condenser and the ambient temperature. You use a compressor cycling switch for R134. Also the GM compressors have a built in high pressure relief valve. Also, overcharges of R12 can create very high head pressure and correct charges of R134 have no higher head pressure than correct charges of R12. The problem with R134 is that if it is undercharged, the outlet temp is high, and if it is overcharged, the outlet temp is high. R12 can be cool with quite a lot of overcharge. Head pressures go up with overcharges or either. R132 is 32 degrees at about 10 psi while R12 is 32 degrees at 27 psi. So obviously you have to watch the low pressure with R134 and the lowest low pressure with the highest spreat with R134 is the correct charge. R12 was hardlly ever done this way because it had more of a window.

A final note. As someone suggested, you can use substitutes for R12, but since they are not in common use with factory cars, it is more of a do it yourself proposition. All the A/C repair shops are used to R134 and I use it because it is cheaper. If I had a special situation of a vehicle that can not run a large condenser (G-body cars have large condensers) it would be a lot more suited for R12 with a much lower boiling point. (Hot Rods, RVs, etc.)

 

[85 Cutlass Brougham]

Yeah, I have the 134a cycling switch ( Napa sells it if anyone wants to know) and the 134a reciever/drier/aluminum cannister thing new in box. I am using a Camaro condenser as it was sitting around and in better shape than my original ( same size, lower inlet/outlet connections by about 2 or 3 inches) and am using the hoses for the 1984 Z-28 with L69 G code engine. I also bought a new orifice tube and the green O rings. I suctioned out the oil from the compressor, condenser and evaporator with a shop vac but plan on using a flush solution through the condenser as I am unsure why I removed the system from the Camaro 10 yrs ago.It's not all connected yet because I am doing the body right now and plan to pull the front clip out a few inches to install the fenders after they are painted ( 2 Door G bodies have a flat black front clip sub structure and the fenders are installed after paint at the factory).All of the inlets and outlets for the various components are sealed off by duct tape right now to keep out debris.

 

[Alanco]

Yeah, I have the 134a cycling switch ( Napa sells it if anyone wants to know) and the 134a reciever/drier/aluminum cannister thing new in box. I am using a Camaro condenser as it was sitting around and in better shape than my original ( same size, lower inlet/outlet connections by about 2 or 3 inches) and am using the hoses for the 1984 Z-28 with L69 G code engine. I also bought a new orifice tube and the green O rings. I suctioned out the oil from the compressor, condenser and evaporator with a shop vac but plan on using a flush solution through the condenser as I am unsure why I removed the system from the Camaro 10 yrs ago.It's not all connected yet because I am doing the body right now and plan to pull the front clip out a few inches to install the fenders after they are painted ( 2 Door G bodies have a flat black front clip sub structure and the fenders are installed after paint at the factory).All of the inlets and outlets for the various components are sealed off by duct tape right now to keep out debris.

All I do when I flush is pour the esther oil in the compressor, then use an air gun to push it through, turn the compressor a couple of turns. Condenser, blow through it with air, then add a little esther oil and blow it through, ditto for the evaporator, and hoses. I buy a quart of esther oil and use a lot of it. You can use the new o-rings, but if you were doing a fresh conversion, you would just use the old o-rings because the traces of the old mineral oil gum up when the R134 hits them, which makes the seal very good. R134 is smaller molecularly, so it leaks easier than R12. Because you are using so much oil, it can get messy especially around a new paint job. The compressor is best flushed off the car, and you can do the evaporator with the hoses on and the condensor off.

Alan