W163 ML350 2003 A/C Problem-- works intermittently
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S6 Avant
W163 ML350 2003 A/C Problem-- works intermittently
Dear Merc-pervs and ML-lovers. My dear 303,000 mile Ml350 is giving me fits with the A/C working only intermittently.
When I first start the car (cold engine) the A/C works flawlessly. Once up to temp, and especially on warm days, the A/C stops working (usually 20 minutes of cold air before this happens),. I still get air from the vents but it is not cold. Based on the little I know about A/C systems, I assumed that after 18 years, it was likely a bit low on refrigerant and, once warm, unable to produce the system pressures needed. So, I took it to my local Bulgarian German car specialist and he evacuated the refrigerant measuring about 400-grams. The spec is for about 750 grams so it was indeed low. Checked for leaks and refilled to spec. Unfortunately, this has not fixed my problem. I am hoping someone here will be able to point me in the right diagnostic direction.
Should I be looking at:
-- Aux fan controller (not sure how they are controlled) although I have checked both the fuse and relay are fine
-- High pressure sensor (Refrigerant temp sensor/switch) 2038300472 (I located this behind the left headlight near the radiator so this looks easy to replace for someone who can evacuate and refill the system)
-- Evaporator temp sensor/switch 1638300272 (not sure where this is located or how to access)
-- Blend door --- This seems highly unlikely to be my problem considering I often get 20-minutes or more of working A/C before the air blows ambient
Thanks in advance!
When I first start the car (cold engine) the A/C works flawlessly. Once up to temp, and especially on warm days, the A/C stops working (usually 20 minutes of cold air before this happens),. I still get air from the vents but it is not cold. Based on the little I know about A/C systems, I assumed that after 18 years, it was likely a bit low on refrigerant and, once warm, unable to produce the system pressures needed. So, I took it to my local Bulgarian German car specialist and he evacuated the refrigerant measuring about 400-grams. The spec is for about 750 grams so it was indeed low. Checked for leaks and refilled to spec. Unfortunately, this has not fixed my problem. I am hoping someone here will be able to point me in the right diagnostic direction.
Should I be looking at:
-- Aux fan controller (not sure how they are controlled) although I have checked both the fuse and relay are fine
-- High pressure sensor (Refrigerant temp sensor/switch) 2038300472 (I located this behind the left headlight near the radiator so this looks easy to replace for someone who can evacuate and refill the system)
-- Evaporator temp sensor/switch 1638300272 (not sure where this is located or how to access)
-- Blend door --- This seems highly unlikely to be my problem considering I often get 20-minutes or more of working A/C before the air blows ambient
Thanks in advance!
