Converting the A/C from R12 to R134a: Reassembly and Installation
Joe Angell
After getting everything out of the car, I had to put it all back in. But with new parts, of course.
Door Flap Foam
All of the foam on the door flaps except the center vents on the air distributor had worn away with age, and needed to be replaced. This foam seals the flaps and makes sure that the air goes where you want it to go with no leaks, so it's good to replace it. We scrapped off the old foam with razor blades, then cleaned the surface with brake cleaner to get the dustier bits off.
For the new foam I used DiversiTech 6-9718 Foam Insulation Tape, 1/8" x 2" x 30' Roll, Black on a recommendation from DMCTalk.org. This is adhessive-backed and easily sticks in place. Two strips covered most of the flaps. The recirculation door required four strips to go around the perimeter.
Scraping off the old foam with a razor, which was then cleaned with brake cleaner.
After installing new foam on the flaps.
Installing the New Heater Core
The heater core goes back into its tray with the hot/cold blend door. You just place the core into the tray, screw the rear bracket back on with two hex screws, and re-install the front bracket.
Of course, there were complications. The plastic around both of the screw holes for the rear bracket snapped off when we tried to secure the core. We wound up using Gorilla Glue to re-mount them, along with some scrap plastic. Basically, just glueing the thin broken edge of the plastic probably wasn't going to hold, so by placing scrap plastic on top of the piece, we would provide more bonding area and hopefully keep everything more secure.
The next problem was the bracket on the front, between the two pipes. This part of the new heater core is taller than the old one, so the bracket doesn't fit. We just bent the bracket a bit and screwed it down without issue.
The tray slid back into the box fairly easily, and we secured it with the two hex screw behind the vacuum actuators, which required a 7mm wrench.
After re-inserting the tray, we covered all the gaps with 3M caulk strips, specifically 3M 08578 Black 1' Strip Calk. This made the box air tight and kept anything from leaking out, although we tried to avoid using as much as the factory had so that we could get the box apart again in the future, if necessary. The caulk is malleable strips that can easily shaped with your hands, and is great for sealing things like this.
There is also a piece of foam that sits between the core's pipes. We transferred this from the old core to the new one, since it was still in good condition.
Gluing the broken ends of the tray back in place.
The new heater core installed in the tray next to the old core.
Sliding the heater core and blend mode tray back into the box.
Repairing the Box
As I mentioned before, we broke the box trying to pry it out, which we could have avoided if we'd removed the defrost vent like we were supposed to. We found the drain hole part and another piece of plastic, and but we lost some other pieces. Luckily, the pieces we had fit exactly where they needed to go. This was sufficient to rebuild the damaged area with a fiberglass repair kit. We did two coats of resin, letting it dry overnight.
Installing the New Evaporator
The evaporator simply sits in the bottom half of the box. Before we put it in there, we transferred the screen from the old one to the new one. It was held in place with hot glue, which we didn't have, so we just used some more caulk strip to secure it.
On the other side of the evaporator is a rubber frame, which we also transferred over.
Next the exposed pipes were wrapped in FJC 2862 30' A/C Insulation Tape, in order to keep the cold in the car as much as possible. The original pipes were wrapped in much the same way.
After that, the seven hex head screws were re-installed with a 7mm socket to join the top and bottom of the box back together. Some gaps were then covered with caulk strip.
The old screen being transferred to the new evaporator.
The pipes wrapped with insulation, and the rubber frame mounted to the evaporator.
The evaporator installed in the bottom of the box, ready to be reassembled around it.
Using more caulk strip to seal up some gaps in the evaporator box.
Joining the Box Halves
With the heater core and evaporator in their respective positions, we just had to join the box halves back together. This requires four hex head screws and a 7mm wrench. It goes together pretty easily.
At this point we remembered the studs that pulled out of the box inside behind the recirculation flap. We were able to use a Dremel with a cut-off wheel to cut out the plastic that housed the studs, which we would later replace with a nut and bolt when securing the box to the car.
The re-assembled box. The foam piece between the heater core pipes can be seen here, as can the seam between the top and bottom halves of the box on the right. This is the side of the box that sits against the firewall.
Re-installing the Box into the Car
This is the best way we found to do it.
First, try to get the pipes through the firewall, which means pushing the box towards the driver's side. Don't push the box all the way up against the wall, though, as you need to run the pressure switch wiring through first. You can try to put the wires though putting in the box, but the wires will probably be in the way.
The early VINs don't have a high pressure switch, but they do have wiring for it. There is a jumper that just has to be unplugged, and the new harness connected to it. We ran this wire in from the outside to make it a bit easier.
Once the wires are run, you can push the box up against the firewall. Before bolting anything in, be sure to align the drain hole with the hole in the frame, unless you want water all over the interior. We didn't quite get the drain plug fiberglassed back in exactly the right place when we fixed my box, so it required some doing to get it positioned, and eventually we resorted to caulk strip to create a waterproof seal around the hole. I believe that the box can be moved a bit more towards the back firewall by adjusting the threaded screw inside the white knob in the picture above, but we decided not to mess with that.
From the fuel tank access in the trunk you can re-install the rubber boot. After spending far too much time this, we again gave up and used caulk strip to keep one corner down. Remember to run the wires through the boot too.
The low pressure switch connector is built into the harness. The high pressure switch connects to a plug, which replaces a jumper present in the early VINs.
Tilting the box into the car.
The box in its final position, but not yet bolted in.
The rubber boot that the pipes and wires go through. The wires go through the left side of the boot as shown here.
With the box in position, the nuts behind the recirculation flap could be re-installed. We put a new 5mm nylock on the one good stud, and installed 5mm bolts and nuts with washers in the two other studs. A pair of 7mm wrenches tightened these down.
Next was the golden bracket below the air distribution box. An 8mm wrench got the two hex screws in, and a 10mm wrench for the two nuts.
After that, the vacuum lines. The two on the side of the box weren't too bad, and could be reached through the driver's side of the car. The rear one is a huge pain, and was best reached by sticking your arm through the gap above the driver's side duct, and pushing the vacuum line back towards you onto the post. I got my hand cut up a little form the edges of the dash doing this.
The defrost vent goes in next. This is pretty easy; it just slides in and gets screwed into place with two Philips screws. the duct from the air deflector aligns pretty easy, and you can reach your hand over the box from the passenger side if you need to adjust it further.
The nuts that secure the box above the blower motor.
The golden bracket installed onto the box, although the nuts still need to be put onto the studs.
The defrost duct installed on the top of the box. The air destructor is removed from this picture, but you don't need to remove it to install or remove the duct.
The defrost vent's final position as viewed from the passenger side, with the duct from the air distributor connected to it.
The recirculation vent is next. I managed to put mine in upside down, which required quite a lot of effort and broke one of the fins. After flipping it over the right way, it went in much easier. Four Philips screws secure it to the body. Don't forget to reconnect the vacuum line.
The blower motor can then be put back in. It's a bit tricky to hold the heavy motor over your head while getting the screws in -- a power screwdriver helps a lot here. After putting in the six hex screws with an 8mm socket, use two more to re-install the resistor. Then plug back in the resistor plug, the power wire and the ground wires, and make sure the vent hose is plugged back into the box.
The newly-foamed recirculation vent re-installed above the blower motor.
I'm doing some other interior work, like a double-DIN touchscreen radio setup, so I'll cover the remaining parts briefly as though it was a stock re-installation:
The driver's side door duct slips back onto the air distributor, and its bracket is screwed back into place behind the steering column with two Philips screws.
The glove box gets screwed back in. I started with the Philips screws around the top, then the hinges on the cover. Make sure to slide the metal spring behind the passenger side hinge so that the door will stay open properly. I then installed the light and its retaining nut. Last was the latch and its two nuts and bolts via a pair of 10mm wrenches. If you install this in the wrong orientation the cover won't lock in place, so be sure to test it before you finish.
The passenger side kneepad goes back on with its four nuts and a 10mm wrench.
For the center stack, start with the ground bundle on the right side. You can then insert at least some of the bulbs, buttons and dials before dropping it onto the two studs forward of the shifter, and re-installing the two Philips screws at the top.
Before putting in the radio, do the center vents. The rubber boots are a pain to get on, but you should be able to do it eventually. You can snap the vents out of their housing to make it easier to do it from the inside. Only then would I install the radio.
Running the A/C Hoses
Getting the evaporator box in and out is supposed to be one of the hardest parts. The other hardest part is getting the new A/C lines in. Some vendors sell split lines, while others sell assemble-it-yourself lines to make this easier. We did it the hard way -- with stock lines built to R134a specifications, after hearing that this is how it is commonly done at DeLorean shops. It also means fewer chances for leaks in the lines, since the hoses were professionally assembled and there aren't any extra joints from the split hoses.
The reason the one-piece hoses are difficult is because they run between along the outside of the frame right next to the fiberglass body. The hose itself is pretty easy, but the connectors have a bend in them that has to slide between the body and the frame while the hose part is pushed down the length of the car. The gap is just barely big enough for the connector to fit.
Dave (The Mechanic) first tried to do this by prying the body from the frame, hammering the hose end with a rubber connector to move it along. I had read that this can be made much easier by letting the frame rest on jack stands, and then jacking the body itself. This separates the frame from the body just a few millimeters, which is all you need to get the hoses through. We tried it, and it made things a lot easier -- they could almost be pulled through by hand, although Dave continued to use the mallet while I fed the hose from behind. The soft mallet did not damage the hoses in any way.
If this doesn't work, you have to loosen or remove the bolts that hold the body and the frame together. The Workshop Manual covers how to do this; we didn't need to.
The hose connector peeking out of the space between the frame and body as we run it towards the front of the car. The bend in the connector very tightly fits through the gap. The metal bar visible behind the connector was being used as a wedge to pry the frame and body apart.
The yellow line shows the path of the hose, with the arrow head pointing at the connector. Jacking the body separates it from the frame just enough to fit it through.
At the back of the car, the passenger side hose is run over the transmission, and both hoses are zip-tied along their length to keep them out way. The hoses run up through a hole in the frame to the compressor.
Compressor
Unlike the 2.8L engine, there is no mounting frame for the compressor -- it simply bolts onto the valve cover. We had to order four stainless steel 105mm M8 bolts to install it. For a moment we thought I had gotten the wrong compressor when the bolt holes didn't line up -- it turns out we just had it upside down, and the holes aren't symmetrical. After flipping it over, it fit perfectly. We also had to replace the blade connector on my new EFI wiring harness with a GM-style connector, which was pretty easy with the kit I had. We zip-tied the wire to the compressor to keep it out of the way.
The hoses connect to the back of the compressor just like they do on the 2.8L engine, and in fact we had to use the plate from the back of the old compressor to lock the hoses in place. The stock hoses easily clear the 3.0L engine's oil filler; some of the third party hoses interfere with it, which is easily solved with some stand-offs under the compressor. [UPDATE: The hoses cleared it because I had them swapped by mistake. Once I connected them correctly, the hose did indeed block the oil filer cap. However, cutting the handle of the cap fixed the problem].
It's worth noting that some compressors require you to drain the oil and refill with compatible polyol ester oil. The Four Seasons compressor I had specifically said that this was not necessary, so we were able to use it as-is. However, it only comes with about half the oil required for the DeLorean’s long A/C system, so more will need to be added later.
A New Belt
The belt I had on the 3.0L was only for the water pump, alternator and crank. I needed a new belt to reach all the way to the compressor. A cloth or flexible plastic tailor's tape measure wrapped around the pulleys where the belt would go. I bought four belts of varying lengths around that size, then returned them all once I realized I read the tape measure wrong by a wide margin.
After getting four more belts, I found that for my application the CarQuest 5060770 serpentine beltfit the best, with extra space on both ends of the alternator tensioning bracket. I'm not sure what the "50" part of the code means, but the "6" is the number of rubs, and "0770" is the length of the belt, in this case 77.0 inches.
Condenser, Radiator and Fans
The new condenser just bolts onto one side of the radiator, and then the fans bolt onto the other side. The catch here is that although the studs look like M5 (which were on the old condenser), they're actually 12-24, and they're surprisingly hard to find locally. I had to order a pack of 50 stainless steel nylocks from McMaster Carr to install it.
I then managed to install my DeLorean Parts Northwest cooling fans upside down. This wasn't evident until we tried to put the assembly back in the car, as the fans hit the front frame extension. After we flipped them over, it fit fine. The fans use a 10mm wrench for most nuts, but 5mm nylocks for the angled brackets. In call cases I used stainless steel hardware, again from McMaster Carr.
With everything back up, we put in the side and top bolts for the radiator brackets with a 10mm socket, remembering to re-install the horns and the ground wire on driver's side angled bracket. Dave also noticed that my new ground bus was running close to the steering rack and zip-tied it out of the way for me. We then plugged the horn wires back in.
The air deflector under the rock screen went in next, which required a bunch of nuts and washers and a 10mm socket. They went in without much trouble.
Replacement bushings for the radiator bracket, from Advance Auto.
The radiator's coolant hoses went back on pretty easily, and were secured once again with hose clamps. There were a couple of points where the hoses might rub against the frame, so we zip-tied some spare hose that we cut lengthwise to them to act as a kind of buffer.
We found that the rubber bushings under the radiator bracket were ruined, but were able to find suitable replacements at Advanced Auto. It is just a simple yellow box that says "Shock and End Link Bushings". Two of them were perfect for the radiator, so two boxes would be needed for all four of the bushings.
Condenser Hoses
The hose from the compressor that runs along the driver's side connects to the top of the condenser. This went on pretty easily with two of the larger wrenches.
The high-pressure hose runs from the bottom of the condenser, over the front frame extension, around the accumulator and into the evaporator pipe that contains the the orifice tube. We just concerned ourselves with the condenser side for now. All A/C hoses were installed with green O-rings dipped in R134a-compatible polyol ester oil.
We eventually realized that this is where the high pressure switch has to go, by way of the adaptor block. For a while we tried to figure out how to install it next to the accumulator, since that's how the original design worked, but you actually do it at the condenser now. The pressure release valve and high pressure switch both mount on this block, with the block sitting between the condenser and the hose. Once we figured its out, it was easy to install.
This image from DeLorean Motor Parts (formerly Special T Auto) demonstrates how the original DeLorean later-VIN high pressure switch assembly worked. This hose design is no longer available.
The new adaptor block installed at the condenser, including the high pressure switch and relieve valve.
Accumulator and Orifice Tube
The accumulator is the very last piece to install. It contains a gel agent in it that absorbs moisture. If you leave it exposed to air too long, it will be ruined by the moisture in the air and you'll need a new accumulator.
The accumulator sits in a bracket mounted to the firewall, which is tightened with two 10mm wrenches. Before tightening the bracket, it has to be mated directly to the evaporator with two larger wrenches. The low pressure switch screws into another side of the accumulator, and the other hose from the compressor attaches to a third side.
I somehow forgot to order a low pressure switch, so I initially just reused the old one, and held the system at vacuum until the new one arrived. The old one probably worked fine, but it was only $10 for a new one from DeLorean, and it was nice to have the entire system be brand new.
After the accumulator is in place, the orifice tube has to be inserted into the other pipe of the evaporator. You can get a special GM orifice tube tool for this, which we did, but we found that the orifice tube went in very easily. It twists to lock into place. The condenser hose then connects to that pipe.
If you ever have to open the system in the future, you have to replace both the accumulator and the orifice tube.
We also took this opportunity to re-install the coolant lines for the heater core, securing them with hose clamps.
Final installation of the accumulator, the old low pressure switch, the new line from the condenser that wraps around the accumulator, and the new compressor line that runs under the accumulator and plugs into the side on the right.
Testing for Leaks
With everything installed, it was time to see if we made any mistakes by seeing if it held vacuum. This would also get any moisture out of the system so that we wouldn't ruin the accumulator.
I bought a cheap set of gauges and a vacuum pump from Amazon. We also got some aluminum R12 to R134a adaptors -- although the hoses were made to R134a specs, they still used original DeLorean R12 hose ends, so we needed the adaptors. It is strongly suggested that you buy steel adaptors, but this was last minute and NAPA only had aluminum ones, so we went with that. Even so, we couldn't get one of the adaptors to fit, so we wound up directly connecting the gauges to the one of the hoses.
We started up the surprisingly quiet vacuum pump and opened the valves on the gauges. We had vacuum in under a minute, which was a very good sign. We closed the valves and left it overnight and vacuum was still held the next day. I left it that way for much of the week while I waited for the low pressure switch to arrive, checking in occasionally and finding that it continued to hold vacuum.
The manifold and gauges hooked up to the A/C lines at the compressor, and a vacuum pump running to pull vacuum on the system.
Filling with R134a
I bought three cans of R134a. The DeLorean needs 2.2 pounds of R12, but due to how R134a works you only need 2 pounds. However, you can't get everything out of each one pound can -- pressures equalize, so you'll generally have an ounce in the can, plus some in the gauges and manifolds, some in the lines, you get the idea. This means three cans are needed.
I quickly found that I couldn’t just hook the yellow line from the manifold up to the cans directly. There are a few ways to get them to connect, but in the end I bought a can side tap. This looks like a set of pliers with point to pierce a can and one or two threaded connections for the hose. You simply place the can inside the pliers (closer to the top of the can, to ensure that you get gas instead of liquid refrigerant), then squeeze them to pierce the can. Once closed, the handles lock against each other. The tap has a Schrader valve, so you don’t have to worry about the gas leaking out before you hook up the hose.
Some people use other refrigerants. You can get R12 replacements, or just compressed duster air cans, some of which are HFC-134a (so, R134a by a different name), while others are R152A. Both tend to be cheaper than R134a sold for refrigerant purposes, and any of those will be cheaper than R12. You can look up the tables for the pressures for those, but I’m going with R134a here.
Note that R134a is a greenhouse gas, is more than one hundred times worse than carbon dioxide. It’s still better than R12 (and far less expensive), as it doesn’t damage the ozone layer, but you should still try to avoid venting R134a to the atmosphere. Unfortunately, this isn’t always possible with the equipment available to do-it-yourself mechanics.
My first attempts at filling with R134a went badly. I couldn’t get refrigerant into the the system, and when I finally did it would bring the low side very high and keep the low side low. It was eventually revealed that I had swapped the high and low hoses to the compressor. There are large “S” and “D” markings on the back of the compressor that I somehow missed. The “S” is the suction side, and is the low pressure gas pulled into the compressor. The “D” side is the discharge side, and is the high pressure gas that has been compressed by the compressor. The “S” side comes from the output of the evaporator on the passenger side, while the “D” side goes to the condenser on the driver’s side. My lines cross over each other, so t get them figured out I loosely attached a zip time to one of them and slid it down from the compressor to under the car where they diverged to the driver’s side and passenger side.
By the time I got this right I had the system open to air for too long, so for good measure I replaced the accumulator and and orifice tube as above. With that done, I vacuumed the system overnight, then got back to filling.
Oiling the Compressor
My Four Seasons compressor came pre-filled with 3 ounces of PAG oil. However, the DeLorean’s long hose run requires up to 8 ounces of oil. There is a fill/drain plug on the side of the compressor. I poured 3 more ounces into it for now; more can be added later as a gas mixture in the same way that refrigerant is added through the manifold set. The O-ring on the drain plug was in good shape so I just reused it, but if there is any sign that it is compressed at all it should be replaced. Note that this needs to be done when the system is empty and not at vacuum, as the refrigerant will get past the oil.
Actually Filling the System
This is the first time I’ve filled an A/C system. It eventually worked, but I’d suggest using other resources for a more definitive result. This is what worked for me, but it’s probably not quite correct. I’d recommend this site for more detailed and complete information.
With everything connected correctly, oiled and vacuumed, the first thing to do Is purge the lines to keep air from getting into the system. Make sure the low side valve at the manifold and and the low side quick-release valve on the compressor are closed. Purge the yellow line by unscrewing it from the manifold manifold until the air is purged and a little refrigerant comes out (as little as possible), then re-attach the hose again. Next open the blue valve at the manifold and loosen the hose from the quick-release valve to force the air out of the line before it gets to the compressor. Finally, tighten the hose and reconnect the quick-release to the compressor, and you’re ready to start filling.
If you really want to do this right, you should now weigh the can. Keep in mind that the weight of the hoses will depend on how they’re resting, and moving them will change the weight
Next turn on the ignition so that the engine will turn the compressor, and set the A/C to max in the cabin to power the compressor and run the cooling fans. Setting up a box fan in front of the car to simulate the the car moving down the road to cool the condenser down further, making it easier to fill the system.
The red high side valve is to remain closed this entire time. The value to the yellow line is opened next, followed by the blue line. Don’t open the blue one all the way — it only needs to be open enough for gas to flow. Once the pressure rises to around 50 PSI, the compressor’s clutch should engage automatically (the big flat disc on the end of the pulley will snap against the pulley, and the compressor will actually start compressing). This should happen well below one 12 oz can of refrigerant. If it doesn’t, you may need to jump the low pressure switch on the accumulator. If it still doesn’t, you have a problem with the power to the compressor. In my case, the pin on the compressor’s connector had come out, and wasn’t making electrical contact. Once I fixed that, the clutch engaged correctly and the compressor could start compressing.
As the compressor runs, the high side pressure will start to go up as the low side goes down. Once the low side drops to around 30 PSI, the compressor will disengage and the low side will rise again. This will repeat until the pressure is equalized between the low side and the can. The can won’t be empty — you can’t get all the gas out — but you can coax a bit more out by heating the can in a pot of hot water. You can also shake the can to get more refrigerant out, but do not shake it too vigorously or tip it over, as that could allow liquid refrigerant into the system, which could damage the compressor. Once the low side gauge stabilizes and the can feels light, you can switch cans. If you’re weighing the cans, you’ll want to weigh now, with the hose in the same position to ensure that the reading is accurate. I wound up giving up on weighing and looked at the pressures instead.
Switching cans has its own process. First close the blue valve at the manifold to avoid having air getting sucked in. At this point, though, the system should have higher pressure than atmospheric (about 14.7 PSI) , so air shouldn’t be pulled in, but it’s good practice, just to be sure, and to avoid having to purge the line again. To remove the can, you have to open the handles. Since you’ve punched a hole in the side of the can with the side tap, any remaining refrigerant will leak out when the tap is removed. Be sure to open the jaws slowly to let it leak out in a controlled manner. If you open it too fast and there’s still a lot of refrigerant in it, the can will shoot off and spin around, possibly harming you and damaging the car or something else in the vicinity. Once the pressure is equalized, you can safely remove the tap and attach a new can. You’ll need to bleed the yellow hose again after the can is attached.
Somewhere around the end of the second can the compressor will stay on and won’t cycle anymore — the pressure will be constant on the low and high side. The problem is that the engine isn’t running fast enough for the compressor to further compress the refrigerant. To fix this, you want to get the engine up to 1500 RPM. I did this by pulling the throttle while looking at the RPMs on my laptop, but a smarter thing to do would have been to adjust the idle so that it was at 1500 RPM.
Once you’re on your third can you want to start playing closer attention to the high side pressures. You’ll be comparing them to an R134a chart, of which numerous are available online. The high side pressure is relative to the ambient temperature. Furthermore, the DeLorean’s high pressure tap is much closer to the compressor than in most cars, which means the pressure will be higher at the gauge because it hasn’t had time to cool down from moving further down the line. I was warned about getting above 300 PSI, and that these test pressure readings should be taken when the compressor is off, and being a bit paranoid I probably put in a bit less of the last can than I should have.
I went for a drive with a cheap A/C thermometer stuck all the way into the vent got the top edge of the green, which is in the low 40s apparently. It’s not as cold as it could be — it’s not frigid like my 2015 Subaru Outback — but the cabin gets plenty cool even on 90 degree plus days, although I am leaving the A/C maxed and the fan speed high. You don’t want it to get too cold — too close to 32 degrees and the evaporator will freeze condensed water and block air flow, keeping the system from actually cooling you. Also, you should test temperatures at fan speed 2, as lower fan speeds allow more time for the air to move over the evaporator and cool more. At some point I should add a few more ounces to get the temperature closer to ideal (34-38 degrees), and adjust the lower pressure switch, but it’s good enough for now. I’m just happy to have working A/C.
Correct connection of the hoses. Note that the low how’s goes to the S (suction) side of the compressor, and the high side goes to the D (discharge) side.
The oil filer plug on the side of the 3.0L A/C compressor. It comes with 3 ounces of oil. The DeLorean system needs up to 8, so I added 3 more. The O-ring should be replaced if at all compressed.
Proper filling of the system. The low side gauge shouldn’t get above around 50 PSI before the compressor engages, which brings the low side down to around 30 PSI and raises the high side.
Getting more refrigerant out of a can of R134a by placing it in a pot of hot water. The side can tap that I used to pierce the can is also clearly visible here.
A vent thermometer reading just at the top edge of the green zone with my A/C running. It could probably use a couple more ounces of refrigerant, but I’m happy with it for now.
Future Work
This is a list of what I should probably do to finish up my A/C conversion.
Add another few ounces of R134a
Adjust the low pressure switch for R134a