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Cost: $100-150 with gauge
Difficulty: 
Time: 1 - 5 hours
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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
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| Procedure |
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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.
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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. |
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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
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| 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.
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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)
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| 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. |
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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. |
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Big thanks to Bill R. and Shogun  |
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