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Retro Air Condition on 735I

06-27-2003, 02:58 PM
The original air compressor is locked solid. Anyone out there have any helpful hints or experience with converting the AC to R134 on a 90 735i?

10-10-2003, 08:07 AM
have the same question too! let me know if you have any answers!

10-14-2003, 08:08 PM
The most important part of doing a/c work is getting everything clean.
I have replaced many compressors and haven't had any problems. The best way to do it is to take the lines and hoses off the car, if possible. I clean out all the lines with a carburetor spray cleaner (CRC, or Master brands are good-- they dry with no residue) and blow them out with air. Some cars have orfice tubes that look like a screened filter, and others have an expansion valve(a square block w/an inlet and an outlet line). When I replace orfice tubes and expansion valves, I use the ones designed for 134A. The pressures are different than that of R-12, which makes the system cool better.
The only problem is that most expansion valves are located beneath the dash and are hard to get to. The evaporator core and condensor core need to be flushed out also. I can't remember the brand, but there is a chemical flush made for a/c systems. If there is a dark, goopy film built up inside of the high-side lines and condensor, the carburetor spray cleaner works good at removing the residue. The condensor core can be flushed out by injecting the chemical into the inlet side and blow it through w/compressed air. I blow it into a shop towel and see if any particles come out in the flush. If there is crap in the system, then keep flushing until it comes out clean. Don't breathe the fumes (or mist), you might want to use a painter's respirator. I have a big fan I use to ventilate the area too. Keep the stuff off the paint, or you'll be paying your body shop a visit.
I use a freon called "Freeze-12" that works excellent in R-12 systems. I run it through my #12 gauges so there is no need to use the adapter fittings. With the Freeze-12 freon, I use the 134-A P.A.G. synthetic oil--do not use the oil recogmended for R-12--. If it is a 134-A system, then I use 134-A freon. Since R-12 systems have a less-efficient condensor core, 134-A will not work. The Freeze-12 seems to work as good as R-12.
One more thing, if there is a lot of crap in the system, then a new condensor core might be a good idea, and always use a new drier.
Hope this is what you needed.

KC Ron Carter
10-15-2003, 05:23 PM
My source for Airconditioner info is

George Martz / Thermal Solutions []


10-20-2003, 12:18 PM
Thanks for the info, It has been a hot summer but now that the fall weather in visiting the east coast, I am not as concerned with my a/c. I am still undecided as to doing it myself or going to the dealer for $1300. On a scale of 1-10, how do you rate the difficulty. Again thanks for the info.

10-20-2003, 07:58 PM
Do you have the tools to take everything apart and an air compressor ?
What kind of mechanical capabilities do you have?

10-21-2003, 08:13 AM
Just basic maintenance exp, tune-ups, changed a few radiators, alternators but nothing as complicated as an a/c unit. I have a friend who has some backyard experience with his bmr and a few specialty tools but I am leaning towards buying the parts and using a real mechanic to do the install by early spring unless it's not that big a deal.

KC Ron Carter
10-21-2003, 09:42 AM

A/C is a very special tool requirement.

I may be able to help with getting you the tools for a small amount of money. I have a kit I can ship.

The big issue is the EPA requirement for the media, freon.
I may be able to help on the media if you are going to stay with Freon R-12 or equal.

Any one tired of paying $400 for A/C charging?

Your cost should be $100 or less depending on needs.

I can supply the kit to vacate and service the Freon R-12 A/C systems.

The vacuum pump is air pressure operated, to save shipping weight.

So if you have a vacuum pump, can attach a 1/4 inch AN fitting to your air compressor inlet, or have access to an air compressor you can service your air conditioner.

I will supply AutoFrost in one pound cans at $10 a can, most will require 4 cans to service. AutoFrost is not an explosive gas so no safety issue please.

I will include step by step instructions to help you do a service.

I can include :
Air operated Vacuum pump
Gauge set for monitoring and attachment
Electronics leak detector, for leaks, MAC over $400.
AutoFrost as required, can opener also.
Instructions to service and correct.
My cost on the kit is over $800 so please insure for that.

In return I will require return of kit on Monday or you will be charged a second week.
I will require shipping UPS ground so next person gets kit on Wednesday.

That allows you to vacate and monitor for leaks for 24 hours and order any parts needed.
One weekend to fix your issues and service.

No laws will be broken and I will make $50 for a week of motherhood.

My best guess cost estimates are,
AutoFrost $10 a one pound can.
Most requiring 4 pounds to service.
$10 to ship to next user or back to me in KC.
$50 for weekly rental.

Your cost should be $100 and that is less than one pound of Freon in most shops.

We will only work with Freon 12 equipment for now.

Freon 134a is cheaper and newer so owners have more money.
I can work up a deal if needed but most have local talent to fix those.

Post what you want but send me e-mail to get on the list.

Those just needing a topoff, bubbles in the sight glass on the drier, then you can just get the AutoFrost and a can opener and line.


Is this legal, yep and I am certified by EPA.
Any one doing this is my agent to correct, operating under my supervision. (


10-21-2003, 12:07 PM
Since my compressor is locked solid I was thinking I didn't have a choice but to do an expensive upgrade to R134. Thanks for the info, i will be in touch when i figure my next move.


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