Aircon R134a retrofit

Problem: My aircon system was empty when I bought the car. I had it charged by a so called "aircon specialist". All they did was put in R134a. The system was empty again after 2 months. So I went back to complain. So they refiled the system, this time with leak detection dye. After about 1.5 months the system blew white smoke from the center grills and the aircon was dead again. I had a look on the internet and found that just filling an R12 system with R134a couldn't posibly work. So I decided to wait untill next summer to have it all "properly" converted.

Background: The early E32s are equiped with an aircon system that uses R12 gas. Legislation in most countries forbid the usage of R12 since mid to end 1990s. This is because R12 contains CFC (Chloro-flouro-carbons) that are harmfull for the environment. In Europe there are three things you can do to get your aircon working again:

  • Drive to Switserland, Poland or some other non EU country and have your aircon filled with R12.
  • Have the system filled with a drop in gas like R413a or R416a.
  • Convert the system to use 134a.

    Converting the aircon system to R134a on most E32 is quite simple. All you have to do is replace the dryer and the old mineral oil used with R12 for PAG oil. BMW has a kit available for this purpose. However some early cars have a compressor made by Kiki-Diesel Zexler for Bosh for Behr for BMW (not so simple anymore huh?). The seals on these compressors contain elastomers that can't keep the R134a molecules in. The retrofit manual lists the following part numbers for unusable compressors:

    Compressors incompatible with R134a
    1 377 9401 377 9411 377 943
    1 377 9441 377 9461 377 947
    1 385 4161 385 9301 386 411

    The drawbacks of using R134a instead of R12 is that it's about 10% less efficient and the molecules are smaller making the system more prone to leaks.

    The older mineral oil used in combination with an R12 system will not mix with R134a coolant and will get into the dryer blocking the system. This can cause servere damage to the compressor. So be sure to get as much of the old oil out as posible. You can unbolt the compressor and pour out the old oil or have a shop flush the system with R12 to remove the old oil.

    Models: All E32s and E34s with an R12 aircon system.

    Fitting the kit:

    Fit the filling adaptors to the old couplings.

    Stick the retrofit label in a place where it can be seen. For a normal E32 it will be the label with 1550 gram on it. For a Highline version with seperate climate control for the rear pasengers it will be the 1700 gram label. The best place is probably the location where the R12 label is now. Be sure to clean the surface before sticking the label.

    Now you'll have to get to the dryer and pressure switches. On cars with the M30 6 cylinder engine you can just remove the airfilter box and then move the washer fluid tank to the space next to it.

    Cars before 2/89 have three pressure switches mounted on the dryer. A high pressure switch, a low pressure switch and an intermittant pressure switch. The updated design only has 1 switch that is used for low and high pressure detection. The intermitant pressure switch will no longer be used.

    You will have to cut off the spade connectors from the intermittant pressure switch,

    solder the wires together and insulate them.

    Install the new dryer with new o-rings on the pipes. Reconnect the electrical connectors, the white plug goes in the white socket, the black plug goes in the black socket :)

    To get as much old oil out of the system as posible remove the compressor and hold it upside down. This should allow most the oil to flow out of the compressor.

    Don't forget the new O-rings when reinstalling the compressor.

    Now you're all ready to get the system checked for leaks and filled.

    Used parts:
    BMW partnrdescriptionprice (1 piece)used amount
    82 31 9 067 396R134a retrofit kit111.061
    64 50 8 390 604O-ring 17.170.871
    64 50 8 390 602O-ring 110.662

    Skills needed/difficulty level: Be sure you know what you are doing. Always have the system emptied by a proffesional before removing any component. Even if you think the system empty. R12 and R134a gas is poisenous and can cause nasty cold burns.

    Story by Johan735.