rogerdc

New user from Florida here. I just purchased a used 2011 E350 and am having intermittent problems with A/C. Sometimes it works perfectly and others it won't kick on after starting the car. Fans all work but warm air comes out. Turning the car off and on eventually fixes the problem and then it blows ice cold.

Does anyone know of any solutions to this problem? I have seen it reported on older MLs and E series as a problem that requires an A/C reset by holding down recirc and defrost buttons with key in position 2 but this doesn't seem to work on this model.

The refrigerant appears to be fully charged.

A/C mech told me it could possibly be a "high pressure switch" but the MB dealer mechanic disagreed.

MB wants to charge me $304 just to look at it so I would rather try other options before I go that route.

Thanks in advance for any help you can offer.

konigstiger

Find independent with MB Xentry (diagnostics) to pull fault codes.

kajtek1

The system has 8 or more sensors that control the performance, so you really need a tool to read them.
Older models would allow reading the sensors on climatronic, but if such option exist on W212, I did not find it yet.
This makes good time to buy scanner.
Now decent MB scanners run in $100 range and sure they pay for themselves in less than one avoided stealer visit.
That said, your symptoms sound like low refrigerant level. Simple gauge can confirm that.

rogerdc

Kajtek, I've looked at several scanners and even the dedicated MB scanners don't seem to pull codes from A/C system, only major systems such as engine, ABS, Transmission, etc. Do you know of any diagnostic tools (other than Xentry) that would be able to diagnose A/C systems?

Thanks,

kajtek1

You choose to not post your location and scanners are like tires - too many choices while too little reviews.
I am using MaxiEcu what is pretty advanced scanner with adaptations and tests, but European-design does not cover some US options.
Lately members gave good reviews to iCarSoft Mercedes/Smart MB II
Bare in mind that W212 is newest technology and lot of older scanners will not help. I am not even sure cloned C4 would cover it.

rogerdc

MB Xentry scan shows no faults. System Pressure at 13.2 bar (191 psi). Refrigerant level normal.

kajtek1

it is 13.2 bar at what stage?
At full AC output you should have 20+, or min 18 bars

rogerdc

It was running at full output. The mechanic looked it up and said it was in normal range for ambient temperature (around 80 degrees), and we confirmed system pressure at ports at 190 psi. If it needs to be at 18 (260 psi) would the system go into fault and throw codes the diagnostic could find? In any case, it looks like you solved my problem. Thanks for that. Heading back to A/C guy to charge up the system.

kajtek1

Variable output AC compressors are hard to troubleshooting and I usually advice 3 readouts in different circumstances for foolproof conclusion.
Bottom line is that you want AC at MAX for such test. That can be done by turning AC to MIN temperatures, but this is not normal setting and I am skeptic about it.
My advise is do a test on hot day, when cabin is in the range of 100F. This way even when climatronic is set to 74F, you will get full AC output for at least couple of minutes. or till cabin temp drops.And for really good test you should have both sides pressure.
With your issue, the AC shop should evacuate the system and charge it by weight. There should be label under the hood that says refrigerant weight, what osciiate around 1 kg.
I did not get my W212 to this stage, but on older cars, when computer senses refrigerant pressure too low, it will shut the whole system down.