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The Detailed E30 R-134a Conversion Thread/DIY

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    The Detailed E30 R-134a Conversion Thread/DIY

    Alright here's a little DIY for retrofitting R-134a in your E30. This is not just a "change the o-ring" type of install, it's a little more than that. R-134a has different characteristics than the R-12 that originally came in our cars. To make it short, R-134a has different chemical and physical properties than R-12. To "compensate" for this, R-134a systems have a different type of condenser, components, and operating pressures.

    An E30 R-12 system has a tube and fin type condenser, as most R-12 systems. A parallel flow condenser is required for R-134a because it can dissipate more heat from the higher operating pressure of R-134a due to a more efficient design, ie: more surface area.

    Below is a pic of the 3 types of condensers used in automotive systems. The diagram should be self explanatory. A serpentine condenser is a combination of the two designs.

    Since an AC system becomes cold by rapid pressurizing, cooling, then rapid de-pressuring the freon gas, the pressure median that's maintained in the system is important. If that median changes due to a leak or in R-134a's case, different behavior under pressure, the system is going to respond with not operating efficiently or effectively. If you have a leak, you find the leak. If you are converting, you need to install a different pressure switch since R-134a's higher operation pressure would render the system not fully functional due to the switch being triggered prematurely. The expansion valve needs to be changed as well as the new operating pressure is outside of the R-12's valve design limits. If you do not, you will most likely blow your old R-12 valve and be left with defunct system.

    A different type of lubrication for the system is required as well. R-12 systems use Ester oil, R-134a systems use PAG oil in various viscosities. Viscosity of the compressor oil depends on the type of compressor. If the system is not lubricated properly, your compressor and other AC components will slowly fail. See the chart farther down for determining your vis.

    As for the o-rings, what's different between them and a standard R-12's is the material they are made of. When R-134a mixes with PAG oil, the chemical make up is harmful to standard R-12 o-rings that are often made up of various types of synthetic rubber. As a result you need a composite rubber that can width stand the higher pressure, higher temperature, and harmful chemical make up. Most R-134a o-rings are made up of HNBR (Hydrogenated Nitrile Butadiene Rubber). HNBR is backwards compatible with R-134a and R-12. A typical HNBR o-ring is green (it's an unofficial standard), but not always the case. I recommend only buying your o-rings straight from BMW or someone reputable.

    One of my blown out o-rings:

    Also worth mentioning are the AC hoses used in the E30 system. If your car was made before 09/1987, it's a good idea to change out all of the rubber hoses as they are not barrier hoses. What does this mean? The hose has an interior lining. R-134a molecules are smaller than the rubber molecules in the hose and as a result will slowly seep out to the atmosphere. In the short term it may be better for you to stay R-12 till you can afford the cost of switching to the newer style hoses. I'm not listing the part numbers for these as they vary depending on the years.

    Now on to the actual DIY since you should now understand the basics of a R-134a retrofit.

    IMPORTANT!: Make sure your system is empty of freon before you begin! It's against Federal Law to release your refrigerant out into the atmosphere. YOU HAVE BEEN WARNED!

    Parts Required for Conversion:
    Parallel flow condenser (ignore the pic) (click here)
    R134a Expansion valve (can be used with R-12)- PN 64511466259
    R134a Pressure switch- PN 64538390971
    Dryer/Reciever- PN 64538391025
    PAG oil- see pic and chart link below for determining the viscosity for your compressor.

    New style compressor bracket idea for M20 peeps -->

    Pressure switch wiring write up is here -->

    • PAG ISO 46 PN 55-9807-905 (Not a BMW listed part number)
    • PAG ISO 100 PN 55-9807-906
    • PAG ISO 150 PN 55-9807-907

    O-Rings- order about 8 each
    • 64501468463
    • 64501468464
    • 64501468465
    • 64501468466
    • 64508390605

    Recommended additional new parts/tools:
    • Evaporator- PN 64511468560
    • 2400+ CFM 14" electric fan
    • a R-12 flushing agent to clean out the lines

    Tools required:
    • Crescent Wrench (another crescent wrench is required if you do not have a 22 or 24mm wrench)
    • 13mm wrench
    • 17mm wrench
    • 19mm wrench
    • 22mm wrench
    • 24mm wrench
    • 8mm socket
    • 10 mm socket
    • 13 mm socket
    • T15 Torx (may or may not be required depending on year model)
    • 6mm Allen socket (Harbor Freight sells these)
    • Phillips head screw driver
    • Air Compressor

    To determine the viscosity of the PAG oil needed for the compressor, you first need to figure out some info on your compressor. Look at the pic below to see how to identify the manufacturer and model family.

    >Click Here for chart<

    This is the compressor off of my M42. By looking at this sticker, I can see that compressor type is a 10PA. So I go down to Nippondenso on the chart and look for 10PA. I look at the column on the far right and it says ISO 46, this is the viscosity of oil I need for my compressor.

    Before you can get started, you need something to measure out the PAG oil. I used a 6oz plastic cup and marked out measurement points.

    Alright now we are ready to actually start working on the E30.

    First things first, the front bumper and valence needs to come off to get access to the condenser. That's already documented, so I'll just link to it:

    Your E30 should look something like this starting this DIY:

    Remove the old condenser, you need to remove the bolts that hold in the radiator support bracket and the 10mm hex bolts holding the condenser to the radiator core support.

    Undo the hoses on the condenser. These are a 22 and 19mm I believe.

    Disconnect the auxiliary fan's connector or what's left of it in my case.

    You can now remove the old set up from the car.

    New vs. old

    Before you install the new condenser, add one ounce of PAG oil to it through one of the fittings.

    Install the same way you removed it.

    Replace the o-rings on the hoses as well as the hose to the dryer if you choose to do so. To tighten the hoses on to the condenser, you need to use some care. The parallel condenser is made of aluminum which is soft. (Your old one is copper, even more fragile) If you start to over torque the fittings they will flex, bend, break, etc. To avoid this, hold one fitting with a crescent and the other with a wrench while tightening them down. These fittings do not require too much torque to make a seal. That's why the o-ring is there. Tighten them till they're snug.

    You can button up the front end afterwards.

    Sitting pretty.

    Remove your washer fluid reservoir to gain access to the dryer and pressure switch. Go ahead and disconnect the rubber and metal hoses. These are 17mm's.

    To remove the metal lines to replace the o-rings and flush the lines out, you need to take off the hood support bracket. This is held on by two 10mm bolts.

    This will give you access to their fittings.

    The metal line running along the fender has two 10mm bolts securing it to the car. Flush it out with compressed air and reinstall with new o-rings. Do the same with the low pressure line running to the compressor.

    Add one ounce of oil to the new dryer and attach the R-134a pressure switch. Be sure to install your o-rings before tightening everything up. Also hook up your new switch.

    Now is as good as a time as ever to remove the compressor to dump out the old oil. It's held on by four 13mm bolts on my M42 powered car. I did not document this process as it varies from E30 to E30 and I had already done it when I had my engine out. :)

    To dump out the oil you just tip it upside down as you spin the compressor. Keep it like this till oil stops dripping out. Look for any particles or dark coloration. These can be clues to a future premature compressor failure.

    Refill with the amount the chart linked earlier listed, minus 2 ounces. These are accounted for in other parts of the system which we already did. Reinstall, tighten up the hoses, and reconnect the clutch engagement connector.

    You're now ready to start on the interior side of this install.

    Here's what you're going to start with.

    There's three 10mm nuts that hold the hinge to the firewall. You do not need to remove them completely, just loosen them enough to pull the glove box out.

    Remove this next. It has two phillips screws and two thumb screws in the rear. You do not have to remove your center console for the next step, but it does make things easier.

    Here's where you'll be working.

    Remove that foamy, tar insulation.

    Remove the smaller fitting first, then the larger one. Be sure to use a crescent to hold and stop the expansion valve from twisting the lower fittings on the evaporator.

    This cover will have to come off to get to the lower fittings, it isn't fun. It's held on by 4 T-15 screws and it can't be broken either. The screw closest to the firewall is quite difficult to remove, so I wish you luck! ;)

    Here's what it looks like out of the car. I used a small bead of silicone along the seal to stop any possible future leaks.

    Note these directional arrows, they're important for reinstall. My expansion valve was replaced before as you can see.

    Now is the time to replace your evaporator if you wish. Mine was good and I just pulled it out a little to get 20 years worth of dirt out and flush any remnant oil.

    Install the new expansion valve with the plastic cover over the top openings. You do not want any foam/dirt getting in there as you secure the bottom fittings. Reinstall the top fittings and replace the cover.

    Be sure to stuff this foam back around the valve. Reinstall your covers and glovebox. The next step is best left to the professionals.

    Charging your newly converted system.

    This part is a bit tricky. Since we are no longer using the factory condenser our R-134a amounts outlined in the official conversion document are a little skewed. The system will also need to be vacuumed out to check for leaks and remove moisture.

    If you fill by pressure rating, my converted system on my old E30 took 28oz of R-134a. My new one as well.

    Your technician should fill by the air temp coming out of your vents. He can match the values of pressure to the relative ambient temperature and humidity to see what your system should be at under those exact conditions.

    However to give him a baseline, I will say start with 25oz and start watching the gauges and vent temps.

    This is the official BMW info document on temps/pressures that you should see coming out of your system.

    Official BMW conversion document courtesy of CorvallisBMW:

    These are the temps I have been seeing on my setup for comparison.

    So there you go. Now enjoy the AC in your E30 all summer long! :)

    Post any questions here in this thread and I'll try my best to answer them.
    Last edited by glucklich21; 07-22-2022, 12:18 PM.

    let me be the first one to say nice job jt.

    EDIT: 21 Jul 2012.

    Today i just finished up this swap. i will start by saying that after a shitload of trouble, i am now for the first time blowing cold a/c.

    about 3 months ago, i purchased a new compressor from an ebay seller for in the range of 150.00 shipped. at that time i also purchased a reciever/dryer and an expansion valve. unfortunately, i purchased the expansion valve before jt published this thread, so i bought the damn r12 unit and it is completely useless. this is to say that with the r12 expansion valve, my air conditioning would produce no cold air.

    after this thread came out, i purchased basically all the parts listed above except for the pressure switch. i don't really think it is required. real oem says that switch is the same for r12 and r134a. also, its only function is to detect about 20+ pounds of pressure in order to turn on the magnetic clutch on the compressor.

    instead of buying the aftermarket fan listed above, i used an oem aux fan from a '90 750i. it seems like a slightly better option since it is 2 speed just like the oem e30 fan. it blows a LOT of air. i have a thread about this in the 24v section. it is tittled "flyboyx's obd2 swap blog"

    i have my own vacuum pump and manifold gauges so i did all my a/c work myself. the system vac'ed down to 30 inches with no problem. i did have trouble once i started filling with freon. both the o rings on the parrellel condenser blew out and i lost a can and a half of freon. i replaced the orings on the condenser with orings that were the exact size that came off the old one. it seems to me that they were too small for the new condenser. i just ended up taking it all apart and putting the next larger thickness rings in place. i didn't have any further problems and the system filled normally.

    the air now blows colder than i need. today was a 90 degree day. i took the car for a spin and i ended up turning the air down. i spent about 400.00 dollars total on parts. compressor, condensor,expansion valve, receiver dryer, freon, dye, pag oil, and orings. this mod is not for the faint of wallet.

    thank you again jt for posting all of your research here.
    Last edited by flyboyx; 07-21-2012, 09:48 PM.
    Gigitty Gigitty!!!!

    88 cabrio becoming alpina b6 3.5s transplanted s62
    92 Mtech 2 cabrio alpinweiss 770 code
    88 325ix coupe manual lachsilber/cardinal
    88 325ix coupe manual diamondschwartz/natur
    87 e30 m3 for parts lachsilber/cardinal(serial number 7)
    12 135i M sport cabrio grey/black


      Damn, great writeup sir!


        Grats on the DIY


          brilliant! I will be using this information. Perfect timing as well!!

          What source did you use for the o-rings? pelican parts?

          Where did you source the fan?

          I assume you just replace o-rings based on the old one matching the new one's diameter?

          How much in total do you think this ran you? 300~? without the refrigeration?


            im plannin on adding ac when i do a 24v swap, my last drive to vegas in the summer was terrible
            nice guide

            Parts for Sale
            YouTube Channel


              Most excellent! Thanks for the write up!


                sticky this
                Your signature picture has been removed since it contained the Photobucket "upgrade your account" image.
                89 E30 S52
                Transaction Feedback.


                  Excellent writeup, this should be stickied as it will be a great resource. It's amazing how much BS and misinformation you see on the boards regarding A/C work...this is spot on.

                  For those that are intimidated by A/C work...don't be. It's actually pretty straight forward, especially on e30's.

                  OP, I have a few questions:

                  What are your vent temps at idle?

                  Do you have a link to the aux fan you purchased?

                  It looks like you didn't reuse the resistor from stock fan (I'm not totally sure you can anyway). If that's the case, do you now have any issues with the engine not reaching operating temp or running too cool (that's assuming the fan runs at a higher speed without the resistor)?

                  Thanks, and well done.

                  For any of you 24V guys, here's where you can purchase A/C hose and fittings to make custom lines:


                  Last edited by mr walker; 05-04-2012, 08:00 PM.


                    Thanks for the compliments guys.

                    The next thing I'm looking into for this setup is a compressor designed for R-134a. The problem that you'll find with this setup is that even though the compressor is 100% functional, etc, at lower revs there's about an 8-14 degree difference in vent temperature. This is because the compressor doesn't move nearly as much freon through the system at lower revs as a compressor designed for R-134a. I'm making an addition to the write up to add some details to this soon.

                    Originally posted by 87' 325 View Post
                    brilliant! I will be using this information. Perfect timing as well!!

                    What source did you use for the o-rings? pelican parts?

                    Where did you source the fan?

                    I assume you just replace o-rings based on the old one matching the new one's diameter?

                    How much in total do you think this ran you? 300~? without the refrigeration?
                    I sourced my parts from Should be $130 or so for that stuff. With everything bought that I listed including the fan, but minus the evaporator, it ran a little over $300 with shipping. Charging was another $60.

                    The fan came from a seller on Ebay by the name of "abad71camaro", this is the second one I bought I from him. I had the same model on my old E30 using this same setup in the DIY for about 6 months and 12k miles (I drive a lot) without any problems. The link for it is here, but I don't know how long it will be valid. >Click Here<


                      Thanks. See the post above for answers about your other questions.

                      Originally posted by mr walker View Post
                      It looks like you didn't reuse the resistor from stock fan (I'm not totally sure you can anyway). If that's the case, do you now have any issues with the engine not reaching operating temp or running too cool (that's assuming the fan runs at a higher speed without the resistor)?
                      Actually I reused the stock resistor. I also installed a lower temp fan switch. My needle stays right in the middle. Without the AC on I never hear my fan kick on and my needle stays the same so I'm not sure how exactly it affects it.

                      This is on a stock M42 with a 88 degree thermostat and 15w50 oil.


                        Great write up! I will certainly be doing this soon. Thank you


                          very nice write up!
                          AWD > RWD


                            my A/C lines are sort of rusty inside, any tips on how to flush them out?


                              Great write up. Should be stickied.

                              SILBER COMBAT UNIT DELTA (M-Technic Marshal)