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BMW 535i Conversion to R134A

Moysiuk on Thu May 15, 2008 10:41 AM User is offline

Year: 1987
Make: BMW
Model: 535i
Engine Size: 3.5
Refrigerant Type: R-12
Country of Origin: Canada

Alright, my R-12 system is still working but will want to convert to R-134A when it fails. I am a mechanical engineer, a home mechanic, understand Automotive HVAC somewhat, and given the correct parts, tools and procedures could rebuild almost anything including the A/C compressor if necessary. So what I am asking in straight terms is what are the options?

From the web I get a lot of conflicting information and need a clear set of instructions and a listing of what new parts are required and what could possiblty be rebuilt to save costs? The car is a hobby car so I can do this at my own pace.

1) New compressor OR new elastomers inside the compressor?
2) New Drier c/w desiccant?
3) New pressure switch?
4) Flush and new oil, (old oil is mineral oil?)

Your help is much appreciated.

Cheers, William

bohica2xo on Thu May 15, 2008 12:05 PM User is offline

1) Flush the compressor completely with oil. See the FAQ's for procedure.

2) New drier, old dessicant is not compatible with 134a.

3) No pressure switch, you have a block type TXV on the OEM system

4) Flush to bare metal on all metal components like evaporator & condensor. Replace any hoses assemblies with mufflers inline, clean any straight through hoses with dry compressed air or nitrogen. Make sure you get all of the flushing agent out of the system before reassembly.


Treat that Behr compressor well, they are not cheap. Rotate by hand while flushing with oil.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

bearing01 on Thu May 15, 2008 4:23 PM User is offline

If you got the Bosch-Behr compressor then it would be wise to change out the compressor's gaskets & seals with updated Neoprene-W or HNBR or whatever. That compressor came with Viton seals that will swell & leak after some time exposed to the R134a. You can get the kit at www.partsamerica.com. Search for Ready-Aire part numbers #2905 and #2916

ice-n-tropics on Thu May 15, 2008 6:09 PM User is offline

Hey Bearing 01,
I perceive this is not your first rodeo. Been messing w/ bearings, have you? Any compressor bearings?
I'm also remembering that comp equipped w/ Viton seals when I was associated with Behr. The Viton absorbs liquid R-134a during the off cycle. When the clutch engages and the suction pressure drops, the seal literally erupts internally and splits it's self apart. I'd try to adapt a Sanden or Seltec instead of messing with the BOSCH/BEHR.
Cordially,
Old IV guy

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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

bohica2xo on Thu May 15, 2008 6:30 PM User is offline

Tex:

I generally tell BMW owners NOT to convert their cars, but this poor guy is in socialist Canada & he has no choice. I had forgotten about the Viton in the Behr units - thanks for jumping in.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

TRB on Thu May 15, 2008 10:15 PM User is offlineView users profile

Can't they use an HC in Canada?

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