W140 A/C Problem - Compressor RUNS ONCE

[teemyob]

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

 

[v8dve]

Not sure if this helps...

Expansion device / drier blocked and cutting out on HP/LP

Clutch / relay not holding

Thermostat signal cutting out

On recirculated does the air temp drop at all in the 3mins?

What pressure you getting at the point it cuts out?

Sorry re eggs but I'm guessing you weighed the charge in and in liquid into the high side?

��

 

[teemyob]

Well,

The condenser was leaking. That was replaced along with the liquid line hose, drier and HP Switch.

All pressure tested with OFN and recharged.

All ran well for one day and then, back to the same issue.

Might have to go to MB or MB Specialist

 

[Vitobrabus]

Moisture contamination blocking the expansion valve. Change the drier and triple vac to hold the lowest torr you've pump will achieve (3torr maximum) and carry out a rise test for 15mins. If it fails, keep breaking the vac with ofn and vac again.

 

[teemyob]

Hi, Thanks for the replies. I will be updating the forum with full details later

 

[teemyob]

It was the NTC in the plenum Chamber

(evaporator sensor)