I want to post and recieve comments about the rebuild of my AC system.

I have done the typical search but would like comments

I have done just about everything thing to a car but work on the AC system. I was going to get my 609 license but while studing for it I realized that R134 was probably the way I wanted to go (see below). I may still get the license for the SL.

I am working on the 1982 300TD. The conversion to R134 was done about 2 years ago and done incorrectly, I know I did it. I added R134 oil and freon with out flushing or removing of oil. So I now face a contaminated system that will have to be rebuilt. The conversion to R134 was done due to a evaporator leak. It was found by the Dealer with a sniffer. I decided to do the 134 conversion to save money, I thought. The car was an airport car and driven about 2000 miles a year. Now it will become a daily driver and the AC must work well.

This is what I plan.
1. A new R4 compressor.
2. New dryer
3. New evaporator
4. New expansion valve.
5. New parallel flow condensor since I will be converting to R134.
6. All the hoses rebuilt at a local hydraulic shop.
7. New high/ low pressure switch.
8. New O rings with Nylog ( R134).
9. New oil and of course R134a
10. The hydraulic shop will build 2 hoses to allow the new condenser to "fit " to the Mercedes hoses. I want to take this approach so that any future condensor replacement will be a easy job. The alternate is to custom make the main hoses or add a manifold to the condensor so the connections are in the current position. The condensor will be from ACKITS.COM

As I said I want the system to work well since this will be my Wifes and my daily driver.

ANY advise on the removal of the evaporator would be appreciated, I understand its a bear.

R134a vs. R12. I know the sytem is designed for R12. The thought process for converting is so that the car can be a DIY. I understand that the problem with the R12-R134 conversion is a lack of condensor size. Stu Ritter of MBCA fame recommends wiring the AC condensor fan to the compressor clutch. They then find the R134 conversion to be acceptable. I want to solve this problem by going with a larger capacity condensor. So the system will be able to handle the R134. Size for size the parallel flow condensor is 33% more capable then a serpentine unit

The sytem will be dismantled.
All hoses flushed, then rebuilt, then flushed again.
Evaporator replaced, and anything in the dash area that needs replacing will be replaced.
New expansion valve.
New compressor installed with the right amount of oil and once the system is closed rotated to prevent hydraulic lock.
I understand about the oil being hydroscopic and will keep its exposure to the atmoshere to a minimum.
All O rings will have nylog (R134) applied.
The system willl be evacuated to 28" here for Dallas, 603'MSL
Then the R134a will be added by weight.

The last 2 items I may not do depending on the cost of a scale and the vacuum pump. I know the compressor type unit is cheap at Harbor Freight and I have a 6HP compressor that can run the cheapo vacuum pump. I will have to look at the scale cost for this one job.

I may consider an inline filter just for insurance. But with everything new I doubt it will be necessary, as long as I adequately flush the hoses.

My decision to go with R134 Vs. R12 was partially due to the cost of the OEM condensor. Even at Rustys or Fastlane it was $250. The aftermarket unit is $85 at ACKITS.com. The hose assembly to make the aftermarket condenser attach to the Mercedes hoses will be about $60 from the hydraulic shop, they say. The aftermarket Parallel flow condensor has the fittings at the top and bottom of the condensor. The Mercedes unit has it in the middle so some kind of adaptor must be made. The hydraulic shop said that they could weld tubes on the new condensor to place the fittings to the correct place. I did read about having to replace parellel flow condensors with compressor failure due to the small orifice size that is use in the parallel condensor. I would rather make up a hose manifold for the connections which would allow easy condensor R+R.
The current condensor is not leaking but sort of beat up, dirty, bent fins and original. It has also had the R134 oil and the R12 oil in there so the acids may have been eating away at the unit.

I have ordered the "new" CD from Mercedes ( its only $99 for the 123 CD) that will have the AC manual and the Electrical manual that I don't have. When It arrives I will surely have more questions.

Any and all comments and suggestions will be appreciated, Maybe not liked, but appreciated.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car