miltak

working on 2008 E350.Ac is not cold enough-left side is pretty warm,right side is little cold.Replaced ac compressor,drier and expansion valve-recharged to specs still the same.Using scan tool-no fault codes in any modules.All flappers read correctly and I even verified visually. There is valve on back of the motor for hot coolant going to cabin-with scan tool I checked function-it clicks when commanded off and on,but cannot be sure it shuts off.The hose is pretty warm on both sides.Not sure what the HVAC looks inside.If it goes through heater block even partially when on cold and the valve doesn't shut off the hot coolant-that would explain.In live data shows evaporator temperature when on low fan at 10 degrees celsius,and ac line is cold,as soon i increase the fan it goes 10 degrees up and the ac line is not cold-like the evaporator is heating up.
Any ideas or experience with this problem.Any help appreciated.I am ASE certified tech with 20 years experience,but this one puzzles me and I don't have factory manual.

miltak

1

kajtek1

https://mbworld.org/forums/e-class-w...soft-mbii.html
Troubleshoot before taking apart.

ot1

miltak

There was pressure,but when ac on,the pressure don't change almost any on both sides,which would suggest bad compressor.
So now I replaced the heater valve as well and still nothing.
I am lost-all system looks fine,but the problem is still there.No trouble codes.The ac just doesn't cool enough.
Does anyone knows what reading is suppose to be on pressure sensor under normal condition on e350?

SethP

I'm having a similar problem. My air is cold, but not cold enough. Took it to the dealership and they said it was a "little low" on freon and charged it up. I can't tell a difference at all, and they say it's working fine.

miltak

My pressures are about 65 psi low side and about 140 psi high side.When AC on almost no change.Also the cooling fan is running pretty low.When tested I can command it with scanner to increase from 10% up to 100% and works fine.BTW really loud anything over 60% and when the ac is on,it runs only about 20-30%,but the condenser is not overly hot,just normal.

EvoTechnik

Are you able to access the hidden menu on the AC?

https://mbworld.org/forums/e-class-w211/691321-w211-hidden-ac-menu.html

What are your readings from the A/C diagnostics menu?

The functions are:
1) in car temp
2) temp outside
3) heater core temp, left
4) heater core temp, right
5) evaporator core temp
6) engine coolant temp
7) refrigerant pressure

ot1

ot1

miltak

I did my readings with scan tool-all were normal-my evap was too hot-only few degrees cooler then ambient on high blower fan and only about 15 degrees cooler on low blower fan.I can command the compressor on with scan tool,but it goes only to 70%.

So now I am guessing I have bad pressure sensor or bad control unit.All lines were checked and there is no restriction in the system.I tried to "overfill" the ac by .5lb and while "overfilling" with my ac machine,I noticed the fan increased speed slightly ,but as soon the machines stop-went back to normal and the temp didn't really change.
My pressure,which is the #7 in your chart is around 11 bars,which is about 160 psi.The only thing I didn't replace is the pressure sensor.I would like to know what it's suppose to be on car this with good AC while running around 80 degrees outside.
Thanks

EvoTechnik

11 bars is still too low. It should be at least 15 bars running at max cool.

miltak

I agree if it's on high pressure side,but why it doesn't go up?
New compressor,new expansion valve,new drier,all lines clear-no restriction-no trouble codes in the hvac system,compressor is opening the solenoid and still not building pressure.If someone told me-those pressures-I would have told him-replace the compressor or expansion valve,which I already did.I am clueless.One thing puzzles me-why the compressor is running only on 70%,why the hvac module doesn't open the solenoid to run it 100% until it cools the evaporator?
Unless the capacity of r134a on hood is wrong-it says .95kg. I tried to add .4 extra pounds,but no major difference,so I recovered the .4 lb back.

kajtek1

How you expect good fix without troubleshooting?
The system operates with +- dozen of sensors , variable output compressor and computer software that has several different programs.
Dropping ins parts- like you experienced does not guarantee results - especially if you don't understand the system.
With variable output you can't judge system by simply taking compressor pressures.
The proper way would be force the compressor to max output and then measure the pressure.

miltak

It won't let me-it allows only 70% output,which puzzles me.The scanner runs complete check with all sensor reading and all flaps showing correct value and also visually inspected,so unless there is glitch in software ,there is something else preventing it to run 100%.
Like I said I am ASE tech with 20 years working on VW/Audi vehicles,which are not that different.-they also use variable compressors,but i have never seen anything like this mess.

kajtek1

MB is leader of automotive technology, so you will find some features on it, that VW/Audi will follow in 5 or 10 years.
You choose not to disclosure your location, so I can only guess that you might be in cold winter. Not good for pushing AC at max.
I installed 4-zones climatronic on my W211, so I can do most of AC troubleshooting on it during driving. The display will show when AC runs at max.
Practical way to test I figured out over the years, is to have car park on hot parking lot, where interior will exceed 100F.
When you turn the engine on, the AC should go to max and that is moment when you should measure the pressure.
You are not having much time as with the system efficiency the temperature will cool down within seconds.
Other way might be turning the settings to LO, but you are pushing the system to work in conditions that it was not design for, what brings margin for errors.

miltak

kajtek1

Very well could be.
MB keeps pretty tight lid on all software features, but we already know that computer can turn AC off on hard acceleration.
So engine code could affect AC performance.

ot1

miltak

Yes,I used our AC machine..950g is actually more then most vehicles with single ac system use.For example most VW use 525g.
That is not the problem.I also added extra,which made no difference ,so I recovered that extra.
Looking at my gauges,I would say I have bad ac compressor,but it was new denso and it has the same issue as before replacing-so it's unlikely.
There was a post for c class with same issue (not cold enough-ac compressor at 70% and fan at 20%) and the MB dealer checked pressures and charge and replaced cooling fan,which they find out later wasn't bad.Then they told the customer it needs ac compressor,which they charged him bunch of $ for and told him it was the problem,but I think they did something else after replacing the compressor and it probably didn't fix the issue and it was MB dealer,which has access to service manual,which I just ordered.
This ac system is actually simple.There is nothing different about this one then any other with VDC.The control module will command the compressor solenoid to open and only other control is the cooling fan.If it works like it should my temperature at evaporator should drop to 30's to low 40's max,which is doesn't. It drops,but not below 50 with lowest blower setting and not below 60 with high blower setting.-that's temp of evaporator,not the outlet,so it is not affected by any possible defective door or mix with warm air,which i have blocked the hose,so be 100% sure (my ambient temp is around 80)
So either the 70% load is not enough to cool-then I blame control module (there is dtc in engine ecu,which could cause it) or 70% should be enough or the compressor and the replaced expansion valve are defective.
Does anyone have reading from live data showing compressor load under normal working condition. (% and amps)

nguyenphananh

Hi I have a question regarding climate control. You mentioned intalling 4 zones climate control. I have a 2007 e350 with standard 2 zones climate control. Is it a direct swap, plug and play?? or does it also involve additional parts installation?? Does it require any coding, progarmming?? thank you

kajtek1

It was P&P on my car.
Works without programing, although car computer recognize different module and shows it on deep car scan.
Now not only the display has more options, including REST, but I can read sensor values on the road. That was prized when I had some AC glitches.

miltak

New update.Customer told me today,that her charging system fault message came on occasionally.That would explain the 70% only and not enough cooling.System would try to save power and run the ac on minimum just enough for defrost.But why it doesn't show it as a dtc.
VW would show system restricted due to fault in other module or to low voltage etc.I guess MB is not that advanced or mechanic friendly.To verify does anybody knows what is max voltage at the compressor solenoid (5v or 12v-VW uses full 12v) I can check the ac by running it at full power.
Thanks

nguyenphananh

Hi Kris, by any chance you have the part number for the 4 zones climate control, and also the part number the the rear seat climate control?? this is look like a interesting mod. BTW, was your car a pre or post facelift?? (do you have the picture of rear seat climate control?). Thank you

kajtek1

2118300685
I did not do anything to rear.
Original 4-zones have ventilation ducts in door pillars.
Mine 2008 is post lift, but I think it does not matter for climatronic.
I'll be selling this car later this year and am thinking about putting factory climatronic back, meaning I might have 4-zones for sale.