[R129 SL] '91 500SL A/C problems

[Peter S]

Hi Rich,
Air-con systems can be a bit of a challenge and hoses and seals do perish or literally fall apart over time.  In my opinion, I would buy the parts, do the work myself, and drop it into the aircon guys to re-gas the system.  I have assumed the compressor pump unit is OK.  It seems that you could also do the work, just make sure that there is no dirt or grit between the seals, and all parts clamp down evenly. 

Regarding changing from Freon 12 to R134.  Why do it?  There are different laws in different countries regarding removal of all the Freon's but the car air-con system was designed for Freon.  R134 is a synthetic gas and we have found that conversion to the R series of gasses does not make the systems as efficient.  A brand new system is more efficient with R series gasses.  (By the way, I am an Electrical, Building and Services Engineer, not a full time mechanic!). 

You are correct that some businesses "never let a cash cow escape unmilked".  I love the expression.  

Sunday morning here in Palmerston North, New Zealand - Cold (7 degrees), Winter, Sun trying to battle it's way through a mirage of clouds, and thunder and lightning storms last night.  High winds about to arrive with more torrential rain and thunder!  

For those who read about Christchurch New Zealand and the Earthquake - we are about 600 km away, and are totally unaffected! (apart from our insurance premiums rising and giving donations).  Christchurch  central business district is a mess, well, half the buildings actually are destroyed or severely damaged.  You would not believe the damage.  Big rifts in the ground etc and about 5,000 houses written off.  heaps of properties are OK though.  main issue was that the Big Quakes are 4 miles directly below the city/ suburbs. If anyone would like some interesting pics, I have a number from friends and co-workers from our Christchurch office etc.

Have a great day.  Remember the 125th Anniversary of Mercedes Benz (Benz Motorcar Patent) will be in Berlin (Germany) in about 6 weeks time.  If you are going, let me know and we may be able to catch up for a Red Wine!  I'm staying at the Concorde Hotel for three days! (It is a 32 hour trip for me one way by air from Palmerston North to Berlin).  Cheers. 

Regards, Peter S. 


  ----- Original Message ----- 
  From: Oldbenz1 at aol.com 
  To: r129list at mbcoupes.com 
  Sent: Sunday, July 10, 2011 11:13 AM
  Subject: [R129 SL] '91 500SL A/C problems


  Recently the A/C in my '91 500SL began to blow warm air.  A local M-B repair facility quoted me more than $2500 for the fix.  The major problem is a leaking hose at the compressor but of course, they apparently subscribe to the philosophy "never let a cash cow escape unmilked" so their estimate included replacing a laundry list of hoses, seals, fittings, dryer, etc., etc. ad infinitum.   Part of the "fix' included a conversion from freon12 to R134.  I've seen kits offered to accomplish this conversion for less than $50.00 and I would guess that the estimate  I received for that part of the job was grossly inflated.  I suspect that to replace the hose in question is one of those things that requires many hours of labor, and I'd bet that suppliers of after-market parts sell the same hose for a fraction of the M-B price.   Here's are my questions:  if anyone out there has been involved in a similar problem, can you give me tips about the difficulty of replacing the hose, and do you have a source for the parts at humane prices?   I have a fair amount of experience and may consider doing the job myself, although I do not have the equipment to charge and test the system once the new parts are installed so would have to have that done by a professional A/C shop.    Any suggestions would be appreciated.  
  Rich Splaine 


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