Could these two be linked?

I’ve read ALOT but haven’t got to the bottom of it yet,

could my AC have ran out and that’s making my fan run on high?

or is that not possible?

I have a 2010 E350 W212 and at the moment it’s turning into a problem a week

 

Usually this is a failed A/C pressure sensor reporting BS to the ECU that then decides to get your attention, "to protect compressor" + "engine overheat" ... anyway the bottom line is the A/C compressor is made unavailable without a valid pressure as seen by the AAC Module.

Repair involves swapping A/C sensor then pumping down vacuum to boil out all traces of moisture contamination.

So it's easy troubleshooting but not really next Sunday's job...
Take 5mn to connect the OBD scanner of your choice and confirm available fault before sourcing spares.


Shortcut:
Presumably if the circuit remains under positive pressure then at no point external air has a chance to get in: no vapor contamination.

Beware:
Refrigerant gas under 150psi pressure means "Risk of injuries", right?

 

thanks for the reply

so for someone who is USELESS when it comes to working on there own car, is this something I can do myself? I believe it’s a case of getting under the front of the car, taking the cover off then unscrewing the old sensor and fitting the new one? The part about the vacuum I have no idea what that means (absolute noob)

also would there be a certain pressure switch I should get? Looking online there are ALOT of variations from £20 to like 60-80

thanks again

 

Do you have a scanner (MB specific would be great)? or Able to get the car scanned for error codes?

You want to check if the AC Pressure sensor @CaliBenzDriver mentioned triggered an internal error code (no CEL light on the cluster). It can also be a short on another part that kicks the fan on (usually HIGH speed). The shorted component should also trigger another error.

It is best you scan the vehicle, report back and we can try to help you. Any AutoZone close by? The scan for free, not certain how good the scanner though.

 

hello!

i have an icarsoft scanner but I don’t really know what I’m looking for? I’ve put it in and scanned but not really found anything?

 

Good.
Is your 4Matic, or RearWheelDrive ?

- Connect to the ODB port
- Select Diagnosis, Mercedes Benz, Lastest version
- Select correct model: E (212)
- Sedan?
- Gasoline
- 212.056 (likely since it is 2010) and NOT 4Matic
- 212.087 (likely since it is 2010) and ONLY if it is 4Matic
- Smart Scan
- Wait while it checks for @40+ modules
- Then visit the AAC (Air condition control module) and see if there is any errors. If any report the error; otherwise, goto Read Data/Live Data (forgot name) and check the values for the different entries.
- Similarly you can visit the FrontSAM module and check for errors

Hope it helps,

 

thank you I’ll try this after work today, shall report back

 

If you want to throw parts at it, around that age it could be:

coolant temp sensor
AC pressure switch at the bottom of the radiator

the hard parts like the compressor/evap core/etc are all pretty rugged, the sensors designed to tell us if stuff is broken end up being the very things that break themselves. It's just conjecture, I would do the diagnostics and see what it ends up being. I just like taking bets to make myself feel smart.

 

I was thinking about doing the ac pressure sensor as that seems quite straight forward but I can’t seem to find any in stock anywhere that’ll actually give me a delivery of anytime this month? Any ideas?

 

SO here’s my results from what you said, I’ll attach photos

first one is the only error code showing up

second is going into the live data

 

Zero BAR is your refrigerant R134A pressure sensor. Assumed this is accurate data.

So you have a leak big enough to drain your R134A all out.
Do not run the AC compressor, loss of R134A is also loss of partial compressor oil, so double bad.
MB WIS has a guideline to what amount oil refill in such scenario.
But you need to address the leak first and this is no DIY job from start to finish.

 

so sounds like this is a garage job? and doesn’t sound cheap either

 

Well, my fear no 1 for AC on our car is, EVAPORATOR leaking. The cost of evaporator is no issue for me, but I do not ever want anyone to tear open my entire dashboard yes entire dashboard,
to access and replace the EVAP.. In the long run, the car will make cricket concert as I call it, from here and there small items being loose or not well mounted.

 

MB cooling fan has two Bosses. Big boss is the engine and the smaller Boss is the HVAC.
Since it is a single fan design, it is thus a shared design.

HVAC SIDE : Fan at maximum sonic speed is a safety measure when and if refrigerant pressure too HIGH, for too LOW I personally do not know, I seen the too HIGH issue.
HIGH can be really high R134A pressure or fake one because on sensor drift/wire broken, like here : https://mbworld.org/forums/e-class-w...mum-speed.html

The refrigerant pressure sensor is not connected to the AAC computer, but to the N10/1 Front SAM computer which is also your fuse box in engine bay.

 

Wonder if we can verify if the pressure sensor reading is "no refrigerant" or "bad sensor" by disconnecting the sensor, and re-scanning the vehicle and see if we get a new DTC. Something along "signal from XXX is implausible" or the like and that was not there earlier. Alternatively, there is the "spit test" (using goggles of course), i.e. take the cap from the low-pressure AC connector, "a bit of spit" and with a toothpick or small screwdriver put pressure on the Schrader valve and see if something comes out.

If the system is empty, this work is not for an inexperienced individual. If the system is still full, we can discuss the next steps here.

 

I’ll get into it this weekend, thanks for the replies

 

It seems these cars have too much refrigerant charge from the factory. I had this problem with the fan screaming in the front of the car and first I thought the refrigerant charge is too low, but it was the opposite. This problem starter with very high almost 100F ambient temperature.

Easy to troubleshoot. Let some refrigerant out thru the low-pressure port and monitor the vent temperature inside the car. It should get cooler if it is the case of over charge. It is easy to add refrigerant back if lowering it first does not help.

Too high charge does not allow refrigerant to evaporate correctly in the evaporator, which process is the one that actually provides the cooling effect.

My low side pressure measured 34 psi and high side 195 psi with 97F outside temperature when it worked fine, and I have not touched it since. This work was done many years ago and it still performs very well.

Too high low side pressure is the problem that prevents the cooling to work correctly.

If you let a lot of refrigerant out remember to add compressor lubricant when you refill.

 

So I have been having the same problem off and on for a couple of years in really hot weather my AC cooling quit and my fan goes on super high

Mine is a 2015 E 63S and I believe I do have a very small refrigerant leak as about every four years I have to put in about one can in the cooling comes right back.

Today it was 95 in Chicago and in the morning when I took the car out, the AC was perfect, but after being parked outside sitting in the sun, as soon as I put the AC on, the fan went crazy.

I had the can of AC charge in the trunk along with the adapter and I put the adapter on the low pressure cord and let it release about 15 seconds of pressure and now the coolant is freezing cold and everything works normal again.

I’m sure I’m not supposed to do that and should’ve taken it to a proper AC shop

But the PSI was reading 450 and now it’s back down to I think like 100

My question is why does this happen when it gets really hot and the pressure goes crazy like that?

 

Unfortunately, you have are repeatedly poisoning your AC system. These systems cannot be recharge by topping them off because there is a solenoid controlled by the ECU, so you are likely overcharging the system. The AC pressure switch is cutting off to protect your AC system before blowing a hose or else.

The radiator fan will run faster as the refrigerant pressure increases until the AC pressure switch cut off the cooling. By releasing gas, you lowered the refrigerant pressure, but perhaps to much and now poor cooling. You need the exact amount.

Take it to an AC shop, evacuate it, find the leak, recharge by exact weight on the label. Hopefully nothing got damaged

 

When the A/C computer reads an extreme pressure it calls for max fan speed.

Extreme pressure is either caused by...:
extreme heat level
overcharged system
a little of both combined

The AC compressor does not cool efficiently when over charged. It forces the succession side to remain up above 40Psi.

450Psi on liquid side is seriously dangerous to deal with. You need refrigerant circuit to be recovered professionally...

 

Super appreciate the feedback. I will definitely get this to a shop as it’s been going on for a couple years and don’t need to blow the AC compressor in 90F heat!

 

@CaliBenzDriver thanks as always, friend for your valuable insights! I let this go because we don’t always have 90° weather in Chicago and that’s the only time it goes crazy

We’ll definitely take it to a shop and get the AC properly serviced!

 

That is the problem of HVAC in countries with HVAC "friendly" weather, it never have to work hard till certain hot and humid season and baked in the sun while being parked....and there then you know its not healthy.
450 PSI high side is about nearly 90C / 194F condenser output temperature.

R134A pressure is temperature based.




I think your compressor has its life shortened by XX percent.
Even me in the tropics, cooled condenser temperature does not go beyond 60C / 140F ( 232psi gauge) in worst stuck zero speed traffic jam at 35C / 95F and humidity of 85% or more.

If radiator fan is running maximum and yet you still see 450PSI ( 90C ) on high side which is COOLED side of condenser, the compressor output surely is above 100C and
the R134A has reached its critical temperature/pressure of 101.1C or 214F. A pressure/temperature R134A no more can be condensed into liquid.
Poor thing your compressor close to 100C /212F its BAD for compressor, 100C+ is a killer for compressor.

If you do not get this fixed fast, a total loss of HVAC system will happen.
I really mean TOTAL LOSS as in 100% HVAC system need to get replaced including all hoses and TXV, Evaporator and Condenser. Only the cabin blower will be OK.
The compressor piston vs liner will be grinding itself and the metal particles will spread to everywhere.....and you can't clean them,
no way to clean them on modern micro channel condenser and evaporator.

I do not know how much will a TOTAL LOSS HVAC cost to replaced in USA, but I I would think the labor is the killer part.
Hardware wise US$2K surely is enough, HVAC parts in USA is cheap even MB genuine/sourced ones.
I said cheap compared to what I have to pay here at 250% to 300% of USA price.

Go and fix it fast please.......