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R134a retrofit

















 

Cost: $100-150 with gauge

Difficulty:

Time: 1 - 5 hours

If your air conditioning in your Bmw E34/E32 currently uses R12 and requires repairs or needs a full refill, you might want to consider converting it to R134 (this is much less expensive than R12).The upgrade requires no more than a new receiver drier, valve adapter, O'rings and a couple of hours labor. If your compressor is not R134 compliant you will have to change it.

Drop In: Lots of different companies sell "drop in" replacement for R12. Lots of people don't recommend it because no AC service center will service your system and "drop ins" are not compatible with anything.

R134 drawbacks: The only drawback of R134 is that the cooling efficiency is not as good as R12, but I am pretty sure that you will not notice it (except if you live in the Death Valley).
Molecule of R134a are smaller and there for more prone to leakage...

Documentation: BMW AC retrofit instructions - R12 to R134a retrofitting

Procedure

The first thing to do is to check if you have an R134a compatible compressor.
Buy the BMW AC retrofit kit (part# 82 31 9 067 396) or all the components needed for the retrofit or repair. BMW Retrofit kits include a new receiver drier, capacity label, the low pressure switch, valve adapters and O rings.
If you change your compressor, check if it is already filled with the right quantity of PAG lubricant.

1. Have a SHOP (not in the driveway) remove the R12 left in the system, don't open it to the atmosphere PLEASE DON'T!
2. Place the new pressure switch included in the kit onto the receiver/drier.
3. Replace the old receiver drier with the new unit with the new pressure switch. (Don't forget to change the O'rings).
If you have a E34 built before 2/1989, you have 3 switches and 6 wires on your old drier. One switch has two wires with two spade terminals connected to it. You will have to cut those two spades, splice the wire ends and solder those two wires together. Then connect the two black and two white connectors together.
4. If you don't change your compressor, remove it and empty the oil out of it, then refill it with new PAG oil.
5. At this point, you should flush the lines to remove oil and contaminants. (Don't flush the compressor or drier). The rubber lines should be changed for barrier hoses also.

3. Install the new port quick-disconnect adapters to the lines. The larger red one goes onto the high pressure side (line from the condenser through the sight glass to the expansion valve).
The smaller blue one goes onto the low pressure side (line from the evaporator to the compressor inlet). With the aftermaket one I bought (I am still kicking myself) I had to remove the little thingy inside the car's ac connectors.

4. Have a A/C shop draw vacuum for 40 min minimum to remove the moisture and ask them to perform a leak test. Charge the system with R134a refrigerant.

If like me you didn't buy the Bmw kit, buy the new capacity R134a label 8-363-255-9

 
Refill procedure in the driveway
1. Make sure that the drier is new, and that the compressor is R134a compatible.
2. Connect the hoses of the gauge set to the right ports, the yellow one going to the vacuum pump.

3. Open all the taps and draw a vacuum for at least 40min.
4. After the vacuum, close all the taps of the gauge set and remove the vacuum pump. Let it sit and monitor that the system hold the vacuum (no leaks)


The right procedure is to pressurize the system with nitrogen up to 50Psi, check for leaks with soap bubble solution (soapy water will do) on all the fittings and connections. If no leaks are found, vent the nitrogen out then connect the vacuum pump. Vacuum for 1 hour min, pressurize with nitrogen up to 10Psi then vacuum for 2 hours, repeat one more time for triple evacuation.
5. Without starting the engine, connect your first can of freon to the yellow hose, then open all the taps. Don't turn the can upside down as the compressor doesn't like to pump liquid, and might break.
6. Go get some very warm water in a pan. When the first can is empty close all the taps, REMOVE THE RED CONNECTOR, if you don't, the can will explode, connect another can, open the blue taps then start the engine with A/C on and high speed fan.
7. Place the can in the warm water as it will increase the pressure inside and will empty faster, switch cans until you empty all four and a half 12oz cans. As the water cool down, change it.
If you don't have a gauge set and charge the system, keep in mind that you don't want air to go inside the system. You will have to pierce the can with the tap on top of it then connect the hose to your system while some freon will exit the can.
While you are at it, check that your engine in not overheating and that the A/C fan is working in both speed.
 
Big thanks to Bill R. and Shogun 
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