S-Class (W140) 1991-1999: 300 SD, S 350TD, 300 SE 2.8, S280, 300 SE 3.2, 300 SEL 3.2, S320, S320L, 400 SE, S420, 400 SEL, S420L, 500 SE, S500, 500 SEL, S500L, 600 SE, S600, 600 SEL, S600L, 500 SEC, 600 SEC

W140 A/C Problem - Compressor runs 3 mins

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Old Apr 10, 2015 | 10:41 AM
  #1  
teemyob's Avatar
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W140 S500, Sprinter 311CDi Traveliner, Sprinter 318CDI Motorhome, Audi A2, Audi A3, Toyota Previa
W140 A/C Problem - Compressor runs 3 mins

Hello,

I hope some of you clever people can help me out?.

I recently purchased a W140 1998 S500. Slowly, I am trying to sort out the various issues on the 150,000 miler.

One of the main problems is the A/C not working.

The Vehicle from what I can gather has been stood for some time. So the first thing was to check the A/C and the system was empty. So, I leak tested with OFN, purged it, evacuated and re-charged with refrigerant.

I then cleared the error codes which were emission sensor and some filter codes. I did have to replace the Emissions sensor as the fault kept coming back up.

The compressor runs, then after around 3 minutes, it stops and will not kick in again. Switching off the engine and waiting around 10-15 mins, the compressor will start again and run for the usual 3 mins.

*I am at a loss as to why it is doing this?.
*No Error codes come back up!
*When the dash is set to LOW - LOW or 14 - 14 warm air still comes out of the side face level vents (not ambient air).

At a moderate 19c ambient I am getting

33.6psi(g) Low Side
190.7psi(g) High side
(When the compressor initially runs)

Any suggestions welcome please ? and I do not mind the suck eggs.

TM
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Old Jun 11, 2015 | 09:04 AM
  #2  
cezarmkd's Avatar
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W140 S500
Check

Check your auxiliary fans. Are they working?
They must start to cool down the temperature and low the presure from the high presure line...
About one minute is enought to bild up a pressure until 14 bars. If the auxiliary fans do not start, then the presure regulator will switch off the AC clutch.
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Old Jun 18, 2015 | 01:59 PM
  #3  
oldsinner111's Avatar
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From: tennessee
s320
you should be at 40psi min.these cars are bad for leaking,add a can of super seal.Be sure to rinse fitting with just freon.
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Old Jun 9, 2018 | 05:36 AM
  #4  
teemyob's Avatar
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W140 S500, Sprinter 311CDi Traveliner, Sprinter 318CDI Motorhome, Audi A2, Audi A3, Toyota Previa
Solved

It was the NTC in the plenum chamber

(evaporator sensor)
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