Oda112

They could try re-flashing the HVAC control unit before recommending the replacement. They wouldn't be making too much money on it but it should have been the first option. Takes 15 minutes.

kajtek1

It is like OJ Simpson lawyers said.
"garbage in, garbage out"
Doesn't look like we are going anywhere.

cetialpha5

He is being pedantic. Technically freon is R12, the new stuff is R134a. You could just say Freon 134a and that would also be accurate.

MBNUT1

Thanks for sharing this. A number of us have had this issue. Keep us informed as you continue to resolve this. And everybody knew what you meant when you said Freon. Nothing lost in the post by that.

vincentv999

This certainly makes sense. I will try to get this done next week. Thanks

vincentv999

Thanks for clarifying. Will definitely update when I get one.

vincentv999

Thanks for clearing that for me. I'm certainly not a tech whatsoever and that understanding was definitely what was needed on that part.

CaliBenzDriver

This HVAC repair is a perfect opportunity for you to find a Benz specialist (Dealer or Indy) that you can trust.
Getting the usual run around : "could not reproduce... come next time" is the wrong way to deal with customers.
AirCon system is not rocket science to troubleshoot... people in the trade use troubleshooting trees to zero in repairs

I believe these E-Class need to worked on ONLY by Benz Doctors because tools, scanner and procedures are really specific!

Get yourself a proper scanner then you can do your research and call the shots... or just pay someone for his time.

As far as AC goes:
- beware that schrader valves are known to leak after being disturbed so your system may go flat after repairs
- In you case clues seem to point to the controller or perhaps the gap on the compressor clutch being too wide...

vincentv999

I finally bought the Climate Control Unit. Will be installing it by the weekend.

vincentv999

Quick update:

Changed the Climate Control Unit Thursday last week. Took 30 mins to do it.

As soon as I turned the car ON and AC ON, cold air blows.

Been using it everyday with no problem.

4 days later, Sunday morning when I turned the car on, I turned the AC ON as well. No cold air comes out. When I started to drive, it starts to get cold. From that point on, the AC is working fine.

Today, Monday morning, same thing happened. I turned the car on and ac on, no cold air. I stepped on to the gas pedal to rev higher and the AC started to get cold and work normal.

It seems like I didn't have to turn the car off and on to have the AC work properly like the original problem that I've been having. This time, I just have to rev the engine to have the AC blow cold and work properly.

kajtek1

That happens when you drop new parts without troubleshooting.
What can we say?

cetialpha5

How long did it take for you to get cold air without revving the engine? The AC compressor is a variable displacement compressor so there's no clutch like in older AC systems. It also takes a little while before cold air starts blowing which is normal.

vincentv999

When I was warming up the car, I turned the AC ON. No cold air blowing. Waited for about 3 minutes until I started to drive and that's when it started to get cold. Today when I dropped off my kids to school, I had to rev up to 3000 rpm in order for the system to start blowing cold air.

Arrie

Wish I had read this thread earlier before you bought the new A/C control.

I had this exact problem. No cold air when started the car. Either had to rev it up or go driving. Normally cold air comes out immediately after start.

Checked the refrigerant pressure and it seemed fine by the bottle gauge, was closer to the low limit though.

Added refrigerant to the upper limit on the green area on gauge and now a very strange thing happened, the fans in front started running full blast.

Thinking from here then went in direction that perhaps the system is over pressurized so I let the pressure down and went slightly below the pressure that the system had when I first started and this seemed to fix the problem.

A/C systems certainly don’t cool if refrigerant pressure level is too low but also it it is too high. Too high pressure in the suction side of the compressor does not allow proper evaporation in the evaporator preventing correct operation of the cooling cycle.

vincentv999

I appreciate your response. No worries on the Climate Control Unit purchase as I only paid $50 ; )

I just spoke to another benz tech and he's thinking in the direction that you just did. This Thursday or Friday, we will flush the system and put new refrigerant in it. Will also check for correct pressure and hopefully fix this problem. Will keep you guys posted.

Arrie

Wish I had read this thread earlier before you bought the new A/C control.

I had this exact problem. No cold air when started the car. Either had to rev it up or go driving. Normally cold air comes out immediately after start.

Checked the refrigerant pressure and it seemed fine by the bottle gauge, was closer to the low limit though.

Added refrigerant to the upper limit on the green area on gauge and now a very strange thing happened, the fans in front started running full blast.

Thinking from here then went in direction that perhaps the system is over pressurized so I let the pressure down and went slightly below the pressure that the system had when I first started and this seemed to fix the problem.

A/C systems certainly don’t cool if refrigerant pressure level is too low but also it it is too high. Too high pressure in the suction side of the compressor does not allow proper evaporation in the evaporator preventing correct operation of the cooling cycle.

kajtek1

MB doesn't have low side pressure sensors, but it does have 1 on high side.
When system is overcharged, the compressor pumps to limit value and then shuts off till the pressure drop.
That gives some cooling, but depends on overcharge it can work on 10% duty, so cooling can be unnoticeable.

Arrie

I'm just posting what happened to me. This happened actually more than once before I lowered the charge pressure. As usually the issue is low charge I check it and the pressure reads at close to low edge of the range on the adjustable (for ambient temperature) pressure gauge so naturally I add refrigerant to be closer to the high edge of the range. No help in cooling and the fan in front of the car starts screaming at max speed I think. I would not know what the real max speed for the fan is but it made noise like never before. I lower the charge pressure down back to that it was and now I get cooling most of the time but get some of these days when I have to rev the engine up or go driving to get cooling to work.

Then again I did the addition of the refrigerant with the exact same result with the fan starting to run very fast. This time I though that it must be overcharged and went down slightly lower than what the charge was and after this I have not had any issues at all with cooling. I get cold air out the vents almost immediately after I start the car no matter how hot it is.

My thinking is that the charge pressure MB use is just very slightly too high causing these problems. You would not think it is a big issue but sometimes you have a need to sit in the car on a hot day without driving it and if you have to be revving the engine up to get cool air in is not right..

For the OP.
If you are a hands-on guy at all do this simple very low cost "trial":
Go to a car parts store and buy a can of the R134a refrigerant and a fill hose with a gauge. Get a gauge that has adjustable scale for the ambient temperature. You can also buy a can of refrigerant with built-in hose and gauge. Start your car and set cooling to LOW, i.e. to the lowest temperature setting. Let it run like this for 5 or so minutes blowing cool out the vents. (A nice other tool to get is a temperature gauge that you can use to check air temperature coming out the vents. I use a digital "gun" for this but there are some very cheap ones too. Having a gauge is not necessary for this, it is just something to see the air temperature difference but if you have the issue I had you can also just feel it by hand).

After car has run the 5 or so minutes with cooling at max cool connect the pressure gauge on the low pressure side of the cooling system. The gauge or hose does not fit other than the low pressure side connection so it is safe. Adjust the pressure gauge scale to the ambient temperature and then it will show you the range where the pressure in the low side should be. You can record the actual pressure reading and with that also record the ambient temperature.

In my car the charge pressure was just slightly (pointer thickness) above the low edge of the pressure range shown by the gauge. I lowered it just slightly below this low pressure range limit and after this I have not had one issue with the cooling.

This is very easy to do and if you feel the charge pressure needs to be back to what it was, well that is why you buy that can of the refrigerant so you can charge it back up.

You may also want to buy a small can of oil charge. Your car is close to 10 years old so it does not hurt to add some lubricant in after you let some refrigerant out. They actually make a can of refrigerant charge with oil included so that would be one to use if you decide to charge it back up.

kajtek1

Living in hot climates I become DIY expert in AC fixing and it gets really annoying when you see 30 or even 100 replies on topic, where OP does everything but troubleshooting.
That gets especially annoying with W210 owners, who can do it on car display, spending about 90 seconds for 2 readouts and they can even monitor AC performance during driving.
Either way, IMHO nobody should start a topic here before he/she gets MB-oriented scanner and reads the codes.
Some kind of brain slap, or what that could be?

Arrie

Just to point out that if the OP's problem is with over charge the scanner would not help at all as, like you said yourself, there is no low pressure side transmitter in the A/C system. Sometimes just an old fashioned "hands on" troubleshooting works best.

kajtek1

Takes about 20 seconds to troubleshoot overcharge with scanner.

jlemyre

I was also having an A/C warm air issue. The first time it happened was while driving back to NJ from Chicago the day after hitting the nasty pothole I had posted about. After driving about 7 hours or so the car began getting warm and humid. I played with the climate control settings, by adjusting temperature, zones, recirculation, turning off and on. Nothing worked, until I made a rest stop and then restarted the car after sitting for about 10 minutes.

This was May 28, 2019. The A/C worked just fine after restarting the vehicle and remained so until the morning of June 19, 2019. After driving about 45 minutes on the way to work, the same thing happened and any manual adjustments failed to correct the problem. I turned the car off just before 7am on Park Avenue at 33rd St and called MB Manhattan to schedule a service appt. They said to come in right in. So I started the vehicle and turning the A/C on auto as I always keep it and it worked just fine.

I arrived at MB Manhattan by 730AM explained the issue and history and that it was working fine now. I also explained that after a few songs the BT connection gets choppy. I figured it was a good idea to have both issues looked into at once and the BT issue isn't as important but nonetheless annoying.

After 2 days, they could not replicate the A/C issue. They uncovered the AC unit in the passenger footwell and found it to be functioning and clear of any debris.

But they found that my 2014 E350S4 required a software update for the COMMAND unit that controls the climate control and bluetooth functionality. So far after a day the AC is working fine and the BT connection has been flawless.

I will update this thread in about 3-4 weeks and hopefully I can report that everyting is operating as new.

THE Rooster

My problem is driver side only, I am finding that if I raise driver side temp to 80-85 for 30 seconds or so & then drop temp setting to Low for 20-30 seconds cold air starts coming out; I then place temp on my desired setting & I can drive in comfort! Passenger side always blows cold air, from starting my drive to the finish.

vincentv999

Haven't been updating since last time I responded. So We finally hooked it up on this machine "Cool Tech" to flush the system out and recharged it. Seems to fix the problem until yesterday. I started the vehicle and switched the AC to ON and no cold air coming out again! I had to step on the gas pedal to get cold air. After hitting the gas pedal, I would hear the compressor kick on.

Does this mean the AC Compressor is malfunctioning? If it is, it should produce a code when it's hooked up on the Benz scanner right?

kajtek1

The computer operates AC base on data from at least 7 sensors. Reading only 2 of them is not telling us much.
You have refrigerant in the system and that's all.