A/C air not as cold as expected
Thread Starter
Junior Member
Joined: Dec 2018
Posts: 69
Likes: 8
From: Texas, USA
M-Class (W164) 2007: ML350 4Matic Gas
A/C air not as cold as expected
Hello,
The A/C on my car (US ML350 2015) seems to not be working as expected. In general under high temperature conditions it seems that it doesnt cool the air satisfactory, esepcially when driving under low revs.
I have checked the refrigerant fluid level and it is ok.
Any ideas on what should I check?
I think for the ML350 W164 there an AC reset procedure. Is there anything similar for the W166?
Thanks!
The A/C on my car (US ML350 2015) seems to not be working as expected. In general under high temperature conditions it seems that it doesnt cool the air satisfactory, esepcially when driving under low revs.
I have checked the refrigerant fluid level and it is ok.
Any ideas on what should I check?
I think for the ML350 W164 there an AC reset procedure. Is there anything similar for the W166?
Thanks!
Out Of Control!!
Joined: Sep 2018
Posts: 14,695
Likes: 4,587
From: unbegrenzt
2017 GLE350 4MATIC
Try an OBD2 scanner to see what's what. If no joy then take it to an Indy or MB dealer for a diagnosis. XENTRY will display all pressures, temperature and actuation statuses.
Members on this site report that a refrigerant recharge is needed from time to time. Maybe this what you need.
Look closely at the hoses connected to the A/C compressor - see if they are weeping oil. That could be a clue the hose(s) need to be replaced, which requires the system to be emptied and recharged.
Members on this site report that a refrigerant recharge is needed from time to time. Maybe this what you need.
Look closely at the hoses connected to the A/C compressor - see if they are weeping oil. That could be a clue the hose(s) need to be replaced, which requires the system to be emptied and recharged.
Last edited by chassis; May 30, 2022 at 09:56 PM.
Thread Starter
Junior Member
Joined: Dec 2018
Posts: 69
Likes: 8
From: Texas, USA
M-Class (W164) 2007: ML350 4Matic Gas
Try an OBD2 scanner to see what's what. If no joy then take it to an Indy or MB dealer for a diagnosis. XENTRY will display all pressures, temperature and actuation statuses.
Members on this site report that a refrigerant recharge is needed from time to time. Maybe this what you need.
Look closely at the hoses connected to the A/C compressor - see if they are weeping oil. That could be a clue the hose(s) need to be replaced, which requires the system to be emptied and recharged.
Members on this site report that a refrigerant recharge is needed from time to time. Maybe this what you need.
Look closely at the hoses connected to the A/C compressor - see if they are weeping oil. That could be a clue the hose(s) need to be replaced, which requires the system to be emptied and recharged.
Any thoughts for the reset procedure?
Out Of Control!!
Joined: Sep 2018
Posts: 14,695
Likes: 4,587
From: unbegrenzt
2017 GLE350 4MATIC
Junior Member
Joined: Feb 2021
Posts: 57
Likes: 13
Metris
Hello,
The A/C on my car (US ML350 2015) seems to not be working as expected. In general under high temperature conditions it seems that it doesnt cool the air satisfactory, esepcially when driving under low revs.
I have checked the refrigerant fluid level and it is ok.
Any ideas on what should I check?
I think for the ML350 W164 there an AC reset procedure. Is there anything similar for the W166?
Thanks!
The A/C on my car (US ML350 2015) seems to not be working as expected. In general under high temperature conditions it seems that it doesnt cool the air satisfactory, esepcially when driving under low revs.
I have checked the refrigerant fluid level and it is ok.
Any ideas on what should I check?
I think for the ML350 W164 there an AC reset procedure. Is there anything similar for the W166?
Thanks!
The engine is started and the A/C system switched on and (generally) set to max A/C, max fan speed, no re circulation mode off, and with just the center vents open and the output air temperature is measured and checked to see if it is within what the car maker calls for given the ambient air temperature.
About all you can do at home on your driveway is to (if the car is equipped with one of course) check and probably replace the cabin air filter. In fact unless you know the cabin air filter is new I'd just replace it. Even if not that dirty a cabin air filter can develop an off/foul odor over time.
Thread Starter
Junior Member
Joined: Dec 2018
Posts: 69
Likes: 8
From: Texas, USA
M-Class (W164) 2007: ML350 4Matic Gas
Regarding compressor hoses leaking.. I dont see any leak..
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Out Of Control!!
Joined: Sep 2018
Posts: 14,695
Likes: 4,587
From: unbegrenzt
2017 GLE350 4MATIC
I read on the internet that there is a "reset" procedure for ML350 W164 (link). I am not sure if something like that applies to W166 as well...
Regarding compressor hoses leaking.. I dont see any leak..
Regarding compressor hoses leaking.. I dont see any leak..
Last edited by chassis; May 31, 2022 at 09:56 PM.
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Thread Starter
Junior Member
Joined: Dec 2018
Posts: 69
Likes: 8
From: Texas, USA
M-Class (W164) 2007: ML350 4Matic Gas
Good that the hoses don't appear to be leaking. No reset procedure has been mentioned on this site. WIS is gospel, so if a WIS procedure exists, that is the one to use. If WIS doesn't indicate a procedure, it doesn't exist. Internet notwithstanding. It sounds similar to a "throttle reset" or "transmission reset" procedure, which doesn't exist in WIS but the internet says otherwise.
Other than that, using my OBD scanner I see that with with 32C outside temp, the vents are blowing at 10C when I am on idle at set ac at max. Also the evaporator temperature is at 7 to 8 C. When I rev the car more than 1000rpm, the evaporator temp drops to 3C and remains constant, while the vents blow at 7C and it feels kind of cooler. Any ideas if that is normal?
Thread Starter
Junior Member
Joined: Dec 2018
Posts: 69
Likes: 8
From: Texas, USA
M-Class (W164) 2007: ML350 4Matic Gas
Out Of Control!!
Joined: Sep 2018
Posts: 14,695
Likes: 4,587
From: unbegrenzt
2017 GLE350 4MATIC
MBWorld Fanatic!
Joined: Aug 2012
Posts: 1,047
Likes: 174
From: Florida
Too many german broads
Thread Starter
Junior Member
Joined: Dec 2018
Posts: 69
Likes: 8
From: Texas, USA
M-Class (W164) 2007: ML350 4Matic Gas
Unfortunately not. In my case the "problem" is there only when the weather is very hot. Under those conditions it becomes much cooler when I rev up the car. We checked freon levels etc and everything lookes ok. Hence it seems more like a weak compressor... but I didnt try to replace it yet...
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From: Florida
Too many german broads
Unfortunately not. In my case the "problem" is there only when the weather is very hot. Under those conditions it becomes much cooler when I rev up the car. We checked freon levels etc and everything lookes ok. Hence it seems more like a weak compressor... but I didnt try to replace it yet...
I had this issue today, warm/coolish air, also a very hot day.. but in my experience with this car, it has never been ICE COLD. Something has always been a little off.
Thread Starter
Junior Member
Joined: Dec 2018
Posts: 69
Likes: 8
From: Texas, USA
M-Class (W164) 2007: ML350 4Matic Gas
The AC on my 2007 W164 ML350 is much cooler
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Joined: Aug 2012
Posts: 1,047
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From: Florida
Too many german broads
I discovered I was a low on freon. I added some regular r134, and it has been OK. Barely used half the can, it could have taken a bit more, but I did not want any possibility of overfill, Anyone else doing this, I would avoid those combo gauge/freon cans as they all have sealer in it, which I did not want in my system. I just used regular old r134 and a reusable hose with gauge.
Last edited by OnlyGerman; Mar 1, 2023 at 09:23 PM.
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From: US
2008 E350, 2012 ML350, 2014 E350, 2015 ML350
Just be careful, these are variable displacement AC compressors; therefore, it is not possible to know if you are low, or high on R134. There is an electronic valve continuously adjusting the compressor duty cycle. You can easily overcharge the system w/o even noticing it.
The standard procedure is evacuation, vacuum, and recharge by weight as stamped in the engine compartment.
In case you do not know, the AC compressor failing in this car is a $1200+ (@$900 Compressor + labor) cost replacement for the compressor alone. Once the system is opened, your dealer or independent will likely suggest replacing the drier, and whatever else may look off.
The standard procedure is evacuation, vacuum, and recharge by weight as stamped in the engine compartment.
In case you do not know, the AC compressor failing in this car is a $1200+ (@$900 Compressor + labor) cost replacement for the compressor alone. Once the system is opened, your dealer or independent will likely suggest replacing the drier, and whatever else may look off.
