Hi all,

BLUF: I'm back with the trouble. My A/C has been working fine, but then the other day I got into the car and noticed it was blowing air that seems to be piped in directly from the deserts of Mexico.

Symptoms: If I put the climate to LO (all the way down) and leave it on SYNC (both sides have the same value) with all other settings on AUTO (this includes the A/C being on), the blower fan goes to max (as does the fan under the hood) and no matter how long the car is left like that, it blows hot air. This also persists even while driving the car. As a result of this I have been driving largely with the climate just turned off and using the backup 4/40 aircon system. Even in this setup, the cooling fan on the engine seems to run at maximum speed quite frequently, only turning off when the engine stops during start/stop operations and spooling back up shortly after restart. The engine temperature gauge does not ever rise above the halfway mark, and the car doesn't seem hotter than usual (except inside the cabin).

What I've done: Read all codes with an OBD-II scanner (not a Mercedes specific one, though, so take that with whatever salt you desire) and found zero stored codes. Other than that, not much, really. I don't know what refrigerant/freon this has (see below) and therefore have not used a cheap A/C recharge kit because the only available ones around are R134a and I don't know if that's right. I also certainly don't want to combine freons.

The Freon Debacle: I cannot tell if this has R744, R1234yf, or R134a. I have access to WIS/ASRA and it gives me this info, found in the safety information sheets listed on AR83.30-P-1760LW (Drain, evacuate, and recharge air conditioning, check for proper operation and check for leaks) E300 Air Conditioner Drain Evac Recharge.pdf:

- Models 205, 213, 253 with code 2U8 (alternative refrigerant) would have R1234yf
- Model 213 with code 1U6 would have R744
- Models 205, 253 without code 2U8 have R134a
- Model 213 except code 1U6 and except code 2U8 have R134a.

That info would lead me to believe that my car (which when the VIN is decoded on https://lastvin.com does not have code 1U6 OR code 2U8) has R134a - in which case this is a trivial matter that I could fix for $30 at the auto parts store. But if I am missing something and this has the 100-Bar R744 system, which from everything I can find online was fitted to all E-Class sedans starting in late-2016 and early-2017, it would be rather unhelpful (and probably, in the end, more costly) to put R134a in a system not designed for it. I also found this website: https://bads.lt/en/blog/technical-in...34a-and-1234yf which is apparently from Latvia but lists all the different refrigerants/freons that are to be used for various Mercedes cars as well as the filling capacities - on this site, it lists the E-Class 213 as using R134a, R1234yf, AND R744, thus confirming the confusion.

What I need: I need someone to tell me what the hell refrigerant this thing uses, and if it's best to drive around in sweat until the dealer can look at it or if I'm safe to use the local auto parts store's A/C recharge to try to troubleshoot, or if there are other steps I should take before I hook a pressure gauge up to it to find out if this problem is even low refrigerant.


And thus I submit my prayer to the Mercedes forum gods. Thanks for reading!

 

I would try a decent diagnosis first as fan running at max speed means a lot. A broken wire from pressure sensor, a missing temperature sensor or anything else.
No need of pressure gauge if you find a a way to properly connect to the car with a diag system.
About gas type, you have a sticker under the hood with all needed informations.​​​

 

First advice with these AC systems, please, do NOT attempt to recharge these systems w/o first emptying completely, vacuum it, and charged Exactly as indicated in the label under the hood. That label should state refrigerant type, and exact weight required.

Without your AC compressor part/model number, I cannot tell if yours has a magnetic clutch or not. My W212, and W166 do, but the W211 does not. It is engine type, and platform dependent. Picture?

Owning an MB-aware bi-directional scanner, either third party or XEntry clone will pay for itself quickly.

Scan for codes, watch for live data. Post it and forum members will guide you

 

You need to have the problem properly diagnosed and not guess at stuff. A/C systems can be complicated and have many reasons for not working. If you don’t know what you are doing, you could do more damage to your car or even break some serious laws.

I recommend using XENTRY and follow the troubleshooting steps. I also recommend joining BenzNinja and have a professional help diagnose your problems.

 

I do have WIS/ASRA but none of the diag tools... hence the trips to the dealer, sadly. I will take a look for the refrigerant sticker, where exactly would it be?

I have always toyed with the idea of getting a Xentry or Xentry clone, but I don't own a windows laptop, which makes getting a working version rather a moot point until I source a win laptop first. Perhaps I will try to source a second-hand Toughbook or something of the sort, but as I understand it, Xentry wants XP or 7, not 10 or 11... I do know that the compressor is engaging, though I forgot to include that in the initial post. Just did a regular "engage AC and watch/listen for clutch" and can confirm it does engage.


Yes, I am aware of the ramifications of doing stupid stuff... that's why I consulted the forums BEFORE I actually touched anything. Now I know to look for the sticker to tell me about refrigerant types. As I said above, I don't have Xentry yet as it's pricey and I lack the hardware. Sourcing that can be done in time but not in a day, so I have to resort to old-fashioned mechanic-ing to determine problems as they arise, without the use of MB-specific diag tools that I do not have. I'll look at BenzNinja but the really obnoxious emoji-laden, photo-filled post they made just two below mine is kind of turning me off, and I would rather own than rent... are they really worth it?

 

You can get XEntry clone and all the supporting tools, DTS, Vediamo, WiS/ASRA, EPC on Windows 10/11 these days.
anything with XP, Win7 is for the older versions which may be useful for certain "use case".

 

You can install Xentry for any cheap Passthru interface into a virtual machine on your MAC

 

I'm thinking I might buy the YOUCANIC scanner I've seen online... it's cheaper than most of the similar ones and doesn't require that I pay extra for certain vehicles, it's bi-directional, and it will do what I need it to do for the most part. Large/intensive repairs are the purview of my dealer, I just don't want to have to take the thing there for every little thing.

I've not had luck with Wine/CrossOver... I've thought about putting it in a virtual machine though but my Macbook Air lacks RAM and SSD space for that. :/

 

This renewed ThinkPad will work perfectly. @BenzNinja provides an SSD with Windows 10 and all the software installed. He then connects remotely and configures the software to run for you. Setting XENTRY up and licensed properly can be complicated. He does it all for you. The license keys are specific to your hardware and sometimes they may get corrupted. If that happens, no problem. BenzNinja will connect in and restore everything. I've run the gambit on XENTRY, WIS/ASRA, and EPC gotten from Asian vendors, and BenzNinja's software has been the most stable and reliable that I have used. He also doesn't use workarounds to get the software working that sets off anti-virus software. Besides the software, you get diagnostic support from someone who thoroughly knows what he is doing.

https://a.co/d/2TGx6y6

 

Before you start adding refrigerant, you need to ensure you are low. If you are, you need to know why. I found the Schrader valve had a leak on my truck and it was losing refrigerant.

The minimum set of tools you need are a set of gauges, a vacuum machine, and a way to recover refrigerant that you evacuate. On the sticker, you will see the type of refrigerant and the amount to add to an empty system. This is the stick on my 2015 SL400. It's right in front. My car uses 550g +/- 10g of R-134a.

 

To complement your suggestion, I take the car to a mechanic with AC service, they evacuate the system, and credit me for the amount taken. I do whatever I need to do in my car, AC or else, return for the recharge and they charged me $120 + extra refrigerant added to reach the value on the label if missing.

I do have my own set of gauges now, but when away from home and helping others, I rent the gauges and vacuum pump from AutoZone, put a deposit that gets refunded when I return the tools. Basically, no cost for tooling. It has worked for me.

and I do still having an independent I trust, but sometimes I want to do it myself (time permitting and within my comfort zone)

 

I worth it as you don't even paying the membership
You get your car repaired
lifetime warranty
Lifetime free repair help, repair coding and flashing
+ you get your car mods for free
Laptop is $100 from ebay

No virus nor trojans

so instead of going the cheapo path with tons of problems....


You are welcome

 

Alrighty, thanks to the suggestions here I was able to confirm I do in fact have R134a. So, that takes the g-whiz CO2 and R1234yf refrigerants out of the equation. Now I can begin to troubleshoot - I know the compressor is engaging. I know the blower motor is working. I also notice the fan under the hood spinning at max RPM all the time, which I wonder if this could be due to the fact that the refrigerant is low and so it’s trying to force the condenser to condense when there isn’t anything (or enough) to condense… just a hunch.

This thread has derailed and devolved into a discussion about how I can’t diagnose or repair anything without an expensive diagnostic solution, and which one is best. Knowing that I do not presently have a diag solution, and knowing that even if I buy one tomorrow it won’t be here the next day, I’m hoping that I can solve this issue without the help of a computer. Tomorrow I will throw a pressure gauge on the low pressure side and test to see what it’s at - if it’s low, I’ll add R134a and report results. If it’s not, I won’t add anything, and will report back again.

In all cases, I already had an appointment on the 16th for a state inspection, so if it isn’t fixed by then, I will have the dealer look at it and, again, will report back with results.

Thanks to everyone who has provided suggestions on both refrigerants and diagnostic solutions!

 

You can pick up a set of gauges at Harbor Freight. You need to measure both the high and low side. This may help you:

Car AC Pressure Chart: R134a Low & High Side Pressures (electronicshub.org)

 

Engine fan will never blow at maximum when the A/C system has low pressure. This is why I already told you to start from electronics. The fan role is to lower the temp (...) this way the pressure ( the risky parameter inside the engine compartment ) will remain LOW. If the pressure is too high or wrongly interpreted as too high because faulty pressure sensor, wires, connectors or AC ECU then the fan will be at maximum.

Also the fan could be defective as well, if with AC Off still blow at maximum.

 

I’ll have to grab some gauges as somehow the shop doesn’t have any yet… clearly we have yet to deal with a lot of A/C issues.

The fan still blows the same when the entire climate system is off, as I described above, which leads me to believe that it might be thermostat related even… if that’s the case would the car disable the A/C system without any lights on the dash/flashing A/C light in order to preserve cooling? Just a theory…

Also, as a general update, I went to the auto parts store today to buy an A/C recharge kit and was informed that my state has banned the sale of R134a because it’s bad for the environment… which is ironic because now I have to drive to the next state over if I need it, which, coincidentally, is also bad for the environment…

 

Cow farts are bad for the environment! What state do you live in?

 

I live in New England, the home of bad winters and worse politics.

I finally bought myself a scan tool that's worth a damn and found the following:

P059700 - The coolant thermostat has an electrical fault or open circuit.
P06DA00 - The actuation of the valve of the oil pump in the combustion engine has an electrical fault or open circuit. There is an open circuit. (I understand this is actually a good thing? No MIL)
P1C5C00 - Battery discharge protection is activated.
*A bunch of TPMS faults as I have two TPMS sensors that require replacement, thus confirming my suspicion that two batteries have died*
P053300 - The refrigerant pressure sensor has a short circuit to positive.

There were a bunch of other random faults for stuff I am tracking already, like the two lights on the rear door handles being out and a couple of other faults I believe are borne out of the ignition being on but engine not started and the fact that the door was open while I ran the codes, but nothing that worries me at all.

So, it appears that between R134a being illegal to sell in my state and the fact that I have nothing with which to capture the used refrigerant, I will have to pay the dealer to do the refrigerant pressure sensor, as the system has to be evacuated to replace it. As for the thermostat, I'm sure I can do that without problems, and luckily for me it has failed in the open position, meaning that the engine takes longer to warm up, not that it overheats. I was surprised to learn that the engine cooling fan being at maximum speed and the A/C not blowing cold were two separate problems that happened at the same time, but not surprised to learn (re: my previous post) that the thermostat is bad. Too bad it's kind of an expensive part! Heavy sigh... at least my car doesn't have major major problems, which is lucky considering how much I drive (~40k mi/yr).

Thanks everyone who has chimed in so far - for the sake of the future person reading this in 2038 who can't figure out what's going on with their car, I'll keep updating this post until the MB dealer confirms what I have found so that I can close out the issue and maybe help someone else in the process. Cheers!

Update: Also for posterity and because I forgot to include it in the previous post, I located the coolant type sticker on the inside of the hood, literally on the underside of it - open the hood and look up. Took me a moment to figure that one out.

 

You have to check the wiring for the refrigerant pressure sensor

"engine cooling fan being at maximum speed and the A/C not blowing cold were two separate problems" is not necessary true.

The coolant thermostat fault code is also electrical.it has nothing to do with open or closed.

Sometimes one little mouse can do the wiring...

 

Test the controls. I got mine back from dealer, it's doing exact same thing. I turned on "ZONE" and a/c worked again. Turning off "ZONE" heat returned, was hot all the way down to 61 on the desired temp control in AUTO.

So I'm in "AUTO" "ZONE" and it cools fine. will get Benzninja to update software soon. No codes, and system blows cold all the way past 77 on both sides. Must be a glitch in the climate module.

My engine fan blows max speed if outside temp is above 95F. If I turn off A/C fan turns off. Scan data shows temps and pressures all good.

Oddly enough, so far, it seems fine since playing with the buttons.

 

MB dealer confirmed that I require a new thermostat and new refrigerant pressure sensor. They quoted $1100 P/L/T for the thermostat and $650 P/L/T for the pressure sensor. I am confident in the pressure sensor but less in the thermostat - anyone have any experience replacing that?

I do not even have a ZONE button on my climate controls... @Rickman30 are you talking about your 2014?

 

Sorry to hear that, did you asked if some wiring harness will be needed too?

 

Time for a trusted independent MB mechanic. The pressure sensor is $50 max from MB original. +$200 max recharge. $650? I know it requires work, but honestly.



https://www.fcpeuro.com/blog/how-to-...ressure-switch

 

Hard to believe that two electrical faults came together without a common cause

 

Upon further investigation, I intend to do the work for both repairs myself - this weekend once I'm back on a regular schedule, I will put the car on the lift and check the sensor before I replace. This should also rule out the two faults being connected, a possibility I have not ignored; though while unlikely, the evidence increasingly suggests that it is coincidence and not a larger electrical fault.