Article by: Johan
Models: All E32s and E34s with an R12 air conditioning system. Includes E31 models with the V12 engine.
Problem: My air conditioning system was empty when I bought the car. I had it charged by a so called “air conditioning specialist”. All they did was put in R134a. The system was empty again after 2 months. So I went back to complain. So they refilled the system, this time with leak detection dye. After about 1.5 months the system blew white smoke from the center grills and the air conditioner was dead again. I had a look on the internet and found that just filling an R12 system with R134a couldn’t possibly work. So I decided to wait until next summer to do the AC r134a retrofit conversion done on my car.
Background: The early E32s are equipped with an air conditioning 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 harmful for the environment. In Europe there are three things you can do to get your air conditioner working again:
- Drive to Switzerland, Poland or some other non EU country and have your air conditioner filled with R12.
- Have the system filled with a drop in gas like R413a or R416a.
- Converting the air conditioning 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 an incompatible 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:
|1 377 940
|1 377 941
|1 377 943
|1 377 944
|1 377 946
|1 377 947
|1 385 416
|1 385 930
|1 386 411
The drawback 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 severe damage to the compressor. So be sure to get as much of the old oil out as possible. 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.
Fitting the kit:
Fit the filling adapters to the old couplings:
Install the new filling nozzles (see part numbers below).
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 separate climate control for the rear passengers 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.
Cars before 2/89 have three pressure switches mounted on the dryer. A high pressure switch, a low pressure switch and an intermittent pressure switch. The updated design only has 1 switch that is used for low and high pressure detection. The intermittent pressure switch will no longer be used.
You will have to cut off the spade connectors from the intermittent 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 possible remove the compressor and hold it upside down. This should allow most of 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.
|BMW Part Number
|R134a retrofit kit
Skills needed/difficulty level: Be sure you know what you are doing. Always have the system emptied by a professional before removing any component. Even if you think the system empty. R12 and R134a gas is poisonous and can cause nasty cold burns.
Remember to put safety first when doing this job!