[AROWHED]

I'm Frankensteining an R-134A AC system together for my 65 Grand Prix. R4 serp belt compressor taken from a 1980s Buick (R12 compressor), turning by hand it has some resistance but feels OK. Evaporator is custom fitted in, its a new part from Rockauto for a 2005 Mitsubishi, with a new expansion valve on it as well. 2 pin pressure switch also new, open at 28 psi and 455 psi. Condensor from a 90s Chevy van. Thoughts..will the system work? Anything missing?

1. Does the compressor need a muffler\dryer with R-134A? It had one in the Buick but Im not using the Buick refrigerant lines nor R12 refrigerant.
2. Can the pressure switch directly handle the clutch coil current, or is a relay needed?
3. I believe the R4 compressor has no oil reservoir, where is PAG oil added?

[Squidward]

I like it. Here are my thoughts:

Any reason why you are using an R4? I would figure there are many varieties of Sanden compressors that are more readily available. Is it a bracket thing?

I don't see mufflers used on more modern systems, so I don't see an issue. My Classic Auto Air system in my Firebird is a thermal expansion valve system, no muffler used. I just repaired the system in my 04 GMC, no muffler there either. I would love to Frankenstein an orifice tube system for max simplicity.

I am guessing you will mount the binary switch on the drier at the condenser outlet. Good. The switches are meant to run in series with the clutch. No relay should be needed.

Make sure to empty all r12 (mineral) oil from compressor and all other components. Use proper oil. You can pour oil into the evap and compressor.

I think you will have a winner.

[AROWHED]

Thanks for the answers. The R4 is quite compact and can be completely in front of the cylinder head to align with the serpentine belt, and set low to not interfere with valve cover removal. I do need to get it a bit lower than pictured for more belt wrap across top of water pump pulley, but will see how it goes as its mounted now.

I see there is another pressure switch on the R4 itself but Im not using it, the switch I'm using (UAC# SW10000C) is on the high side refrigerant aluminum tubing. That tubing was taken from a 2008 Toyota RAV4 and it also contains a sight glass. That UAC part has the same threads as the trinary switch that was on the RAV4 line.
I do need to configure a receiver dryer still. Plumbing all this will surely be interesting as well.

[Squidward]

I think this is cool!

Understood on the R4. Space is a premium.

I like the use of common factory parts. Aluminum liquid lines can be bent pretty easily

Are you using a factory evap case from your GP?

And how did you come up the Mitsubishi application to fit the case? Did you internet search based on sizes? Junkyard crawls for an evap are NOT the easiest!

Keep us posted!

[AROWHED]

Yes on Pontiac factory evaporator case, although you can see in the pics I made a metal plug for where the old refrigerant lines went through, then cut a new hole lower for the Mitsubishi evap. It really didnt take much to make it fit there. I chose it because (backing up four years here) my daughter somehow grenaded the trans in her 2008 RAV4. Before junking the whole car, I pulled the still good engine and all the AC parts, with future transplanting the AC system into the Pontiac in mind.
Found out later Toyota uses variable displacement compressors, and didn't want that....but also its evaporator just would not work well in the 65 Pontiac housing, due to the way the refrigerant lines attached. So I spent some time combing through Rockauto looking at all these Japanese car evaporators until finding one that looked workable, the Mitsubishi Montero part (UAC# EV939539PFXC). Installed it with a new expansion valve and luckily the Toyota hard lines were a match for it there too.
But I dont know what happened to the receiver dryer from the Toyota...I don't even recall what it looked like or where it was located flow-wise in that system. Or if it even had one at all!
I did find a video about changing out the R4 compressor seals to R134A compatible parts: https://www.youtube.com/watch?v=1zZyeEgDdyY The Santec parts needed are #MT2119 and MT2038 (single lip shaft seal...there is a double lip too but I havent found its number yet.)

[AROWHED]

Just remembered I used the RAV4 condensor, not a chevy van...getting old age CRS. The Toy part has reciever dryer built in..so jsut need to change out its desiccant bag.

[Squidward]

Excited to see how this performs. TXV systems usually make for very cold air, but have increased complexity and cost vs CCOT systems. I'm hoping you get super frosty temps!

What oil are you going to use?

[AROWHED]

UPDATE: With Summer bearing down I finally got around to finishing this AC system up. I bought a new R4 compressor from Rockauto, for R134a, and it came labeled as pre-charged with 3 ounces of PAG, but it did not state what viscosity. I added 4 more oz of PAG 46 into the suction line, and a new dessicant bag into the Toyota RAV4 condensor . Pulled a vacuum and it held at 30" overnight. Added two 12 oz cans of R134a this morning. With it 85F outside today, it was blowing 60F air out the vents at idle, hood and doors open, both electric fans running. Compressor case got pretty hot though, 200F by infrared thermometer, so I shut it down and let it cool off for several hours. Just went outside and hooked up the gauges, with engine off getting a 100psi on both sides. Started engine, AC on, low side started climbing towards 100 and high side was pushing over 300 and still moving up quick so shut it down fast. I should note here that the dual electric fans had not kicked on yet, so there was practically no airflow through the condensor. Now that its been off 15 minutes both gauges are back at 100, which it is my understanding is normal. But running you dont want to see much over 50 on low side or 300 on high. Was two cans too much? Or should I set up a large blower fan on the condensr for all testing? Something else?

[Squidward]

I would set it up for a better driving condition sim, with some airflow through the condenser.

I've always used the ambient temp as a rough thumbrule for the static hi/low pressure. So 85f should be roughly 85 psi. This holds roughly true until you get up around 100f. So it looks a little excessive on both sides.

Try airflow first to see if both sides come down. Beyond that, it seems a little overcharged. It looks like 18-22 oz is the range for most 2005 Mitsubishi models. So 24oz could be on the high side if you got ALL of it in.

You are in uncharted territory, so a slow add after the first can is the name of the game.

[SRGN]

I would set the fans to run on high whenever the compressor is on, this is standard configuration on a lot of cars. Most of the R4 compressors have a spot to add a high pressure switch, I believe the default is to plug the port with a round metal plug retained by a snap ring. 80s g-body cars used the high pressure switch, IIRC it's normally closed and opens when pressure gets over 300+ psi. You can use the high pressure switch to ground the compressor clutch, that way if the pressure gets too high the clutch disengages. With both fans on, pressure at the high side should be around 230 psi on the high side at 85 degrees ambient. 35 on the low side should be about right. Again, you need to have airflow through the condenser, or the pressure readings will be useless. You may need to adjust the system pressure, but getting air through the condenser should be the priority.

['ol Pinion head]

All regular production '80 & 81 Birds with LU8 301 Turbo engines were built with the Frigidaire R4 compressor. On some 400 equipped '78 Bonneville's, instead of the traditional A6 compressor,
Pontiac used the R4 compressor. Other than a small cast alum bracket that mounts to the side of the head, the specific '78 400 R4 brackets interchange with the later 301 R4 pieces . One can even use stacks of
washers & longer bolts under the 301 R4's small alum bracket & it will properly bolt to side of the front of the passenger head. For a thorough diagnosis and trouble shooting of the R4 systems,
the '78 Pontiac Service Manual goes into it in great detail. The '80 Pontiac Service Supplement mainly addresses the packaging of the remote accumulator/ different refrigerant hose routing for the LU8 engine.

[AROWHED]

As usual, you gentlemen are correct. This morning I added a third electric fan directly on the condensor, wired to kick on with the compressor. The dual Spal fans on the radiator do well for engine but the condensor is about 5" ahead of it, and they don't generate sufficient airflow through it as well. Photos shows the results, about 78F outside when photo was taken and engine had been idling for about 8 minutes. 25 psi low, 175 high, bouncing around 45F at outlet ducts with blower fan on high. Good amount of water dripping out of evaporator housing. After a short test drive I noticed the outlet ducts were frosting up, as it is pretty humid today. Gonna call it good for now, thanks all for your advice!

[hgerhardt]

Nice job! My retirement "job" is supplying A/C systems for small airplanes, so I did all the same mix-n-match of components as you did. I'm using a variable-displacement clutchless compressor from a Toyota driven by an Arduino. If you really want to get the charge level correct, you'll have to measure superheat and subcooling in real-time as the car is driving. I did that on my airplane with these bluetooth probes: https://trutechtools.com/JL3KH6. Before I learned about these, I got my system to where I thought the charge was close by using just a manifold gauge set, but turns out I was quite a bit low.

However, I'm more interested in your serpentine belt system. Is that the same as that dude here did a few years ago or is this your own setup?

[AROWHED]

Yes, the serpentine belt setup is a variation of the "Junkyard" system that came out on PY years ago. Pulleys are Ford Crown Vic at the crank and water pump, 95 Chevy pickup at PS pump, VW for the CS144 alternator, a Gates #38145 tensioner, and a couple Four Seasons #45926 idlers. Mostly homemade bracketry and spacers, functional but not real pretty. The best part is it takes 1 minute to take the belt on\off, and I can take the AC compressor out of the loop if necessary with a shorter belt, as it was just a week ago.

[Squidward]

Originally Posted by AROWHED

Yes, the serpentine belt setup is a variation of the "Junkyard" system that came out on PY years ago. Pulleys are Ford Crown Vic at the crank and water pump, 95 Chevy pickup at PS pump, VW for the CS144 alternator, a Gates #38145 tensioner, and a couple Four Seasons #45926 idlers. Mostly homemade bracketry and spacers, functional but not real pretty. The best part is it takes 1 minute to take the belt on\off, and I can take the AC compressor out of the loop if necessary with a shorter belt, as it was just a week ago.

Awesome!

I actually have most of that stuff sitting around from when I used to go yard crawling. I was gonna do it at one point, but gave up.

I run a factory setup, but use a Sanden compressor with a v belt. Not ideal, but it works.

Any other pictures of the setup?

[AROWHED]

Here is a few bad pics from my cheap phone. Tried to show all spacers and brackets. Power steering: 1972(?) brackets, and a big spacer to offset from cylinder head, yet still allows pump to pivot. Belt tensioner: Lower bolt supported by a piece of 3/4" square tubing that is held on stand-offs on three lower water pump bolts, partially visible in pic. I recently added that aluminum brace to the upper as the long 5/16" bolt was beginning to bend since the longer AC belt is pulling tensioner even tighter. The heavy CS144 alternator required a secondary upper bracket to keep it from deflecting some with belt tension and my right foot, so I half-assed that extra slot bracket in there after twisting it in a vise, mostly as a test but it worked so left it there. There is a ridiculous number of spacer washers everywhere that fine tuned the belt alignment. Now that its set it would be prudent to weld up dedicated one piece bracket\spacers since taking this apart is a PITA to keep track of every single part's location.