Introduction
The Mercedes E-class air conditioning is a complicated system of blower motors, computers, relays, switches, and refrigeration parts. With a system this complex, it’s likely that you’ll encounter an air conditioning problem at some point during your ownership. Thankfully, the onboard climate control computer has a self-check mode that can help you quickly diagnose air conditioning problems.
To make troubleshooting easier, I’ve written a software program that will analyze the results of your climate control self-test. All you need to do is follow the instructions, enter the values and trouble codes, and (hopefully) get your diagnosis.
Skill Required
Level 1: Mirror Fogger. If you can follow simple directions and have full use of at least 10 of your 20 (or 21, as the case may be) digits, you can do this job. Too busy? Delegate this project to your 11 year-old. Just make sure he doesn’t drive the car through the living room wall.
Tools Required
Pen and paper.
Parts Required
None.
Instructions
Part 1 — Collect Sensor Data
First we’ll get the values of all the various climate control sensors. These sensors constantly monitor data like air temperature, refrigerant pressure, etc. Odds are if something’s wrong, a sensor will pick it up. Let’s get started!
Start your car.
Press the “AUTO” button on your climate control.
Turn on the A/C (i.e. “EC” light must be off; if the light won’t shut off, continue with this test. We’ll address your “EC” light on the next page.)
Let the car idle for about 3 minutes.
Set the temperature on each side to 72°F. You can do this quickly by pressing both the red and blue arrows simultaneously.
Press and hold the “REST” button for five seconds or until the left side of the display says “01.” The left side indicates which sensor you’re checking. In this case, #1 is the in-car temperature sensor. The right side of the display shows the value of sensor #1 (in this case, the actual in-car temperature).
Press the “AUTO” button on the left side to move to the next sensor. Press the “AUTO” button on the right side to move to the previous sensor.
Record the ID number of each sensor (left side of display) and its corresponding value (right side of display). For example, in the picture on the right, you would record that sensor #5 has a value of 6.
You only need to do this for sensors #1-8. You can write down the values for the other sensors, but they’re not really related to air conditioning function.
When you are done, press the “REST” button again to exit the self-check mode.
Part 2 — Collect Trouble Codes
Now that we have all the sensor values, let’s check the computer for malfunction codes. Read this carefully, because you have a 20 second window after switching on the ignition to load the trouble code display mode.
Ignition must be switched on. 20 second timer starts.
Increase the left side temperature (left red arrow) until left side says “HI.”
Decrease the right side temperature (right cold arrow) until right side says “LO.”
If your 20 seconds passed, switch off the ignition and switch it back on. Your HI/LO settings will be preset. Timer restarts.
Press and hold the “EC” and “REST” buttons simultaneously for at least five seconds.
The screen will go blank.
Load the first code by pressing the right side “AUTO” button.
If you have any error codes in memory, the screen should look like the figure on the right. The ‘E’ stands for “error.” In this case, we have error code B1234.
Write down each error code. To cycle through the codes, press the right side “AUTO” button.
When you finish, press the “REST” button to exit.
Part 3 — Send Me Your Sensor Values & Trouble Codes
Use the comments box below to provide background info on the problem, sensor values, and error codes. I’ll take a look at them personally. I can’t guarantee that I’ll know the answer to your problem, but I’ll give it my best shot.
Part 4 — Buy Me a Beer
I’m a Mercedes enthusiast, and I do this for free. You may save hundreds of dollars in the process. Although it is certainly not required, I always appreciate a “thank you” in the form of a nice, cold beer. If you’d like to buy me a beer (or a nice bottle of wine), click on the button below:
Vehicle info and problem particulars:
2000 E430 Sport. Driver's side air blows whatever is outside (i.e., warm/hot). Passenger's side is getting cool, but not as cold as it once did. Slight hissing noise at times behind the vents (i.e., emanating from the engine compartment).
Sensor values:
1 – 92
2 – 102
3 – 92
4 – 86
5 – 92
6 – 198
7 – 16
8 – 141
Error codes:
b1227
b1234
anybody getting any responses ?
I'm in the middle of moving cross-country and will begin addressing
questions once I'm settled back in!
My boyfriend figured out what was wrong with our air conditioner, but I was going to post about our troubles here. I just wanted to say, I think it’s really great what you’re doing. It’s so cool that so many people have responded. You’re very nice!
David- Please help with my 98' E300!? I drive this thing everywhere and I have went 3 weeks without air. Here are the codes:
VALUES
1-32
2-35
3-72
4-71
5-34
6-83
7-24
8-65
CODES
E61 R227
E61 231
E61 232
E61 234
E61 235
E FF
Any help would be greatly appreciated!! I will help you move if you can crack this one. I am driving this thing 1000 miles a week and I am riding in a hot car with hot beer, where would you like me to send it
2001 e320
Sensors
1 – 82
2 – 76
3 – 112
4 – 114
5 – 143
6 – 188
7 – 03
8 – 103
Codes
E61 234
E61 416
E FF
Thank you so much for your help! Help me out and I'll donate to the cause! =)
I released the pressure of my system then recharged with R-134a to about 40psi. The initial read was about 65psi. Can't get anything cold out of my car.
I sure hope you're able to find this post! I'm not sure why it isn't posted on the top/bottom.. It's just floating out here in the middle.. =(
Hi,
Your main problem is a faulty evaporator temperature sensor. It's reporting an implausibly high temperature (#5=143 degrees) which is causing the A/C system to shut down to protect the evaporator core from freezing. The computer does this when it determines that the evap temp sensor is unreliable.
Your refrigerant pressure (#7) looks low. It's hard to say whether your system is adequately charged or not based on pressure alone. Once the compressor is running after replacing that evap temp sensor, you'll have a better idea. Note that you need the compressor engaged in order to charge the system since the (relative) suction from the compressor on the low-side line is needed to draw the refrigerant out of the can.
Blake
thank you so much for your help! i think it's absolutely awesome that you're willing to help out those of us in need! you can expect a few beers from me!!
Hey Blake first, thanks for being such a great resource and money saver, here are my codes:
1-87
2–87
3-85
4-87
5-84
6-136
7-00
8-85
EB1234
EB1241
EFF
Thanks for your help!
Ray,
Looks like your system is empty and needs to be recharged. The
refrigerant pressure sensor is reporting zero pressure. Sometimes this
is caused by a defective sensor, but that happens rarely. Look
through my previous responses for instructions on how to bypass the
pressure sensor and how to reset the codes if you want to give that a
try before recharging.
If your system is empty, the most common source of leak is the receiver-dryer.
Blake
I sent in a question 2 months ago, if you have time could you please check it out and give me some advice. Thanks for any help.
Hey Blake, I have a 1998 E300 TD.
Symptoms are: A tiny bit cold for the first 3-4 minutes, then blows whatever air temp seems to be outside.
First about the faults. I had a bunch of faults that I was able to clear out to a E-FF status with zero showing. A Winter ago I had Firestone replace the Serpentine belt which is where I think the problem might have started. Also checked using my CodeKey ODB reader and no codes thrown.
Here are my error codes, 1st reading is after 3 minutes, 2nd reading after 20 minutes driving to work. These are in Celsius on the left, Fahrenheit on the right in parens:
sensor 1- 37, 36 (98.6, 96.8)
sensor 2- 32, 30 (89.6, 86)
sensor 3- 40, 37 (104, 98.6)
sensor 4- 40, 37 (104, 98.6)
sensor 5- 77, 77 (170.6,170,6)
sensor 6- 37, 95 (98.6, 203)
sensor 7- 08, 08 (bar)
sensor 8- 33, 42 (91.4, 107)
Since sensor 7 reads only 8 bar, so I'm thinking that with no fault codes I might just need a recharge and the problem could be a leak somewhere. A confirmation would help.
Does anyone have a link to the 210 parts numbers for all the sensors?
Thanks in advance,
Jesse
Fairfield, County, Connecticut
Jesse,
In short, your problem is the evaporator temperature sensor (#5). Replace that and you'll be back in business.
Look through my other replies if you are interested in a more comprehensive explanation of why this sensor causes this problem.
Blake
Thanks Blake, I came to the same conclusion last night after adding a can of 134a only to have the compressor blow much colder air for approximately the same short time span of a minute or two,
thanks for your help, donation to the Blake Cameron Wildlife Preservation Fund to follow. :>)
Jesse
Hi Blake,
The E55 has been sitting relatively idle. I have replaced the sensors and had the unit charged. EC light is not on. Air temp sensor in front, even after replacing shows error, though I can read outside temp on instrument cluster.
What's the next step – vacuum leak, head unit, ?
Thanks
John F. Burr, Ph.D.
Continuous Term Lecturer
Krannert School of Management
Purdue University
615 Carrolton Blvd
W. Lafayette, IN 47906
765.404.4114
Mike,
Thanks once again for the beer money. I have good news for you. It looks like all you need is a recharge. None of your error codes are significant. The only one that might make a difference to you is B1231, the engine coolant temperature sensor. That sensor informs the climate control unit when it's appropriate to start blowing (hopefully warm) air after staring the car in the winter.
As for the air conditioner, your refrigerant pressures look good. The vent air is warmer than it should be (40s), but still cool enough (60s) to tell that the A/C is working. Often when the refrigerant is low, you'll hear a hissing noise emanating from behind the center vents and notice a temperature difference between the left and right center vents. A simple recharge should put you back in business. In the interim, you can try using the recirculate button to reduce the temperature of the air being drawn through the AC (assuming the interior is cooler than the outside).
Blake
I have '98 E-320 which gave a problem with the high speed fan motor not comiing on. The blower motor was changed by the dealer a couple of years ago for a hefty sum of $1200. Starting late last year the AC would just not cool. All I am getting is the hot air. I am hesitant to take it to the dealer because the price will vary from $297 (recharge) to may be $4500 (coils replacement). I read your artical and decided to take down the readings and see if could recharge 134a myself. Here are the readings:
#1 30,#2 29, #3 31, #4 31, #5 49, #6 65, #7 01, #8 28.
The error codes are: E61 227, E61 231, E61 233, E61 234, E61 459, E FF, E.
The EC light can be turned off. If you feel that the rfrigerant needs to be recharged, would you let me know the approximate location of the low pressure valve? I have opened the hood andcan see a chrome pipe going from the compressor to the body below the brake fluid cup. This pipe has a valve with a plastic thread cover.
Thanks in anticipation.
SK
I have a '98 E320. Two years ago the high speed blower was replaced by the dealer for a hefty $1200. Late last year, before the Fall, the AC stopped working blowing only hot air. The EC light can be turned off. I was told by the dealer that the recharge will cost me nearly 297 and the worst case scenario is $4500 for changing the coil. I was encouraged to read your article and decided to take down the sensor readiings and the error coses to see if it is indeed just the recharge that is needed. I think I can recharge it myself if I can confirm the location of the low pressure valve. I had looked under the hood and found that the chrome pipe going from the compressor to the dash just below the brake reservoir has a valve with plastic screwed cover.
I have collected the sensor information and the errorcodes per your guidelines. Here they are:
#1 30, #2 29, #3 31, #4 31, #5 49, #6 65, #7 01, #8 28.
The error codes are:
E61 227, E61 231, E61 233, E61 234, E61 459, E FF, E
I will appreciate it if you can put me inthe right directions. Thanks in anticipation.
SK
EC light stays on. No A/C.
1-40
2-35
3-49
4-48
5-45
6-68
7-00
8-34
Error codes read
Eb1 234
Eb1 241
E FF
Either a small 'b' or a '6'.. Help please.
Brian
Brian,
You need a recharge. Sensor #7 shows zero pressure and error code 1241 indicates the need for a refill. Sometimes this is caused by a faulty sensor rather than an empty system, although that is less common. If you hook up a pressure gauge to the low-side service port, you can confirm the actual pressure in the system.
Blake
Hi Blake, Great stuff and great site. The info here is fantastic.
I just changed the receiver dried on my 1999 e320 and recharged the system with
1 can containing 396 grams of product including 2.5 oz of oil, plus 2 more
cans containing 340 grams of 134a each. I am getting some cold air
but no icy cold air is coming out.
I had to reset the ec light in order to refill, and I did the same with
error codes (no error codes were present anyway).
I thought the amount of 134a would be enough but the gage on the can says 40
when it should be over 50 according to the outside temperature of 82°.
Should I add more refrigerant to the system or I have another problem?
Here are my values with the car parked and just turned on.
1 – 85
2 – 82
3 – 71
4 – 71
5 – 60
6 – 134
7 – 15/16
8 – 109
No error codes.
With the car on the road for 30 minutes (data taken while driving)
1 – 67
2 – 85 (goes 94 when stopped on red light)
3 – 42
4 – 42
5 – 39/42
6 – 199
7 – 11/13 (goes back to 16 when stopped for red light)
8 – 89 (goes above 100 when stopped for red light)
The controls were set for 61° on auto for both sides.
When I was resetting the error codes, e FF appeared, but also d FF appeared
at some point and the air recirculation light started blinking. Is this a problem I
have to be worried about or not a/c related?
Again, thank you very much and the beer is already there for you.
Katarina,
Thanks for the beer! Great job recharging it yourself. You put in the correct amount of refrigerant. If you were to add more, you would reduce the efficiency of your system (too much is in some ways worse than too little) and might actually get warmer air.
Your numbers look perfect. The unfortunate reality is that you will never get “ice cold” air from a Mercedes air conditioner. Your evaporator temperature is 39 degrees (#5) and the vents are 42 degress (#3 & #4). That's the design temperature.
If you're not getting adequate cooling, consider whether your blower fan speed is adequate. The blower regulator burns out periodically and lowers the fan speed as it fails. You can tell when it's failing if the fan speed does not increase with each step when you manually adjust it. At max speed, the airflow should be strong.
The 'FF' code that you see indicates the end of the list. If that's all you see, that means you have no error codes.
Blake
Hi Blake,
I have a 2001 E430 and a/c does not work, out side temperature around 90-95, low side gauge pressure 45psi and here are the sensor information.
1-94
2-127
3-103
4-58
5-53
6-193
7-17
8-138
The error codes are EB1234 AND EB1235
Thanks,
Ahmet
Hi Blake
I have 1996 E 200
I have Refilled the car with 1 Kg Feron
and the Reading of the 5 is Always 02, 01 C on the Auto while in the Manual low fan It drops to 0C and i can hear the Compressor stops working . this happenes very fast as the car didnot get well cooled. once you turn on the Ac you can see the reading from the 5 goes to zero very fast.
On the Highest Fan it didnot drop to zero on spot .
7 shows 14 to 17 Bar.
I have done a Vacum test and there is no leaking .
what do you think?
Hi Ahmet,
Your duovalve needs to be cleaned. The duovalve controls the heater. It's stuck in the on position for the left side. The heater is overpowering the air conditioner. There are DIY instructions online. Either Google “w210 duovalve cleaning” or look through my other comments on the website to find a link to a how-to guide.
Blake
The evaporator cannot work below 0C because the moisture in the air will turn to ice. That ice will block the evaporator and potentially crack it. The compressor turns off as a safety mechanism to protect the evaporator. Slow air movement lets the temperature drop more quickly. Keep your fan speed up and you should be fine. If anything, your A/C is working too well. A leak would not cause this.
Blake
Thanks Blake for you Prompt reply.
But my issue is that why i turn on the Ac from Off on the Low fan it drops to zero in a very very short time even the temprature inside the car is Hot
so i think that there is a problem here.
i think that there are should be not less than 4 or 5 what do you think?
other note running the Ac on the hight fan ( 4 or 5) is so noisy.
is there any faults in the sensors or somthing.
also there is 2 errors b1416 , b 1421
Was the system empty when you recharged it? 1 kg is the total capacity. If you added 1kg to a partially empty system, it's overfilled. That may be your problem.
Hi Blake, I posted this a couple of days ago, but I dodn't see it here. So I'm posting again. I have a 2002 E430 and its blowing only hot air. These readings were taken in my garage, (it was 102 outside). I had just driven the car. When I see post you can expect a cold one…Great site 1 – 103 2 – 107 3 – 116 4 – 109 5 – 119 6 – 206 7 – 00 8 – 138 e61 234 eFF
Hi Blake, I'm posting this again haven't seen any reply on the original post. I have a 2002 E430 and its blowing only hot air. These readings were taken in my garage, (it was 102 outside). I had just driven the car. – 103 2 – 107 3 – 116 4 – 109 5 – 119 6 – 206 7 – 00 8 – 138 e61 234 eFF
Sent you a beer.
Thanks
Hi,
Thanks for the beer. It looks like you need a recharge. The
refrigerant pressure is showing as zero. Rarely this is caused by a
faulty sensor, but nine times out of ten the sensor is ok.
Blake
Ok here we go again, I've got a 2000 CLK320 and air is not cold at all during our 90 degree weather. I took the codes the first time, followed the directions and bought some freon it said it was low so I added some and it went up a little but still no cold air, got under hood and compressor is engaging and no ec light on. I am giving codes for before and after freon.
1. In car temp sensor – 26
2. Outside temp sensor – 89
3. heater core temp sensor (left) – 10
4. heater core temp sensor (right) – 100
5. Evaporator temp sensor – 97
6. ECT sensor – 163
7. Refrigerant pressure (bar) 7
8. Refrigerant temp sensor – 97
Error code E FF which is no error
AFTER Freon added today
1. In car temp sensor – 26
2. Outside temp sensor – 89
3. heater core temp sensor (left) – 101
4. heater core temp sensor (right) – 101-104
5. Evaporator temp sensor – 85
6. ECT sensor – 187
7. Refrigerant pressure (bar) 9
8. Refrigerant temp sensor – 103
I checked for error there are none. Definetly worth buying you a beer to get my wife off my #$@
Two things:
Set the temp on both sides to 'LO' to force cool air instead of allowing the computer to turn on the heater.
1) It's possible you didn't add enough freon. Your evaporator temperature is still too high and the pressure is not as high as it should be for a full load.
2) Your in-car temp sensor is broken. If the climate control computer thinks that the car is 26 degrees inside, what temperature air do you suppose it will choose to blow?
Hi,
Having a E430 -98, with only warm air from the A/C.
Here are the values:
#1 24
#2 23
#3 46
#4 42
#5 25
#6 82
#7 00
#8 31
Error codes:
E61 231
E61 234
E61 235
E61 459
E61 423
E61 424
Thanks / Magnus
Magnus,
You need a recharge. Your refrigerant pressure (sensor #7) is zero. Rarely, a zero reading is caused by a faulty sensor rather than an empty system. But most of the time, it's true.
Blake
1=107, 2=89, 3=93, 4=94, 5=123, 6=173, 7=06, 8=97
fault codes
E61 419
E FF
Thanks for your help
Paul
parsroe@juno.com
Paul, At a minimum, you have a defective evaporator temperature sensor. Often when that sensor goes bad your A/C will work for a few minutes and then stop. That semspr needs to be replaced, which will hopefully fix all your problems. Blake
Thanks! Here goes for my 99 E300, which seems to be having a bit of trouble keeping the interioir cool:
Sensor Values:
1 78
2 96
3 67
4 64
5 129
6 157
7 29
8 182
Codes:
E61 234
E61 235
E FF
Then the codes repeat
Ambient air temp: 90 degrees.
Cool but not COLD air blowing from vents.
Beer waiting.
Joe McGuire (mcguirejwatcomcastdotnet)
Hi, Your refrigerant pressure & temperature look way too high. Did you by any chance add extra refrigerant to the system? Your evaporator temperature shows 129 degrees, which is ordinarily impossible. I suspect that your evaporator temperature sensor is faulty, though it is hard for me to tell given the high refrigerant pressure.
Blake
Blake, I would love to contribute to your beer fund.
I have a 1998 E320, I had the refrigerant added today at an auto shop they said it was 0. At first start up A/C works for about 2 minutes then shuts down.
My sensor data is as follows
1-40
2-36 (funny its 94 outside now)
3-33
4-28
5-71
6-90
7-goes from 23 up to 30 and back ( is this too much pressure)
8-67
My trouble codes were
E61 227,231,234,235,459,424
(I did the reset and it now has now trouble codes)
EC was never stuck on
Tried doing the bypass for the refrigerant pressure sensor that did not help (from 157 to 173)
Fat Tires are the best beer.
Harold,
Your temperatures readings are in Celsius. Your main problem is the evaporator temperature sensor. Replace that, and you should be in business.
Blake
Mark, you need to replace your evaporator temperature sensor. That will solve your problem.
C. Blake Cameron
hello,Blake !
I live in Portugal and we have a lowt a good bear and wine waiting for you.
I nead you help…
I have a clk w208,98
ec it´s block
ac work´s but d´ont cool
1-31
2-39
3-33
4-33
5-60
6-94
7-8
8-42
9-000
10-00.8
11-E
12-E
20-0.20
21-007
22-000
23-000
24-13.3
40-055
41-016
42-120
43-032
the error are
eb 1234
1235
1235
1416
1459
1422
1241
can you help me ? please…I think you stay fan of the portuguese wine !
Hi,
Your evaporator temperature sensor has malfunctioned. It's reporting an implausible value (sensor #5) which is causing the A/C to shut off. Replace that sensor and everything should start working again.
Blake
Hi-
Here are my readings, appreciate the help. Compressor not engaging.
1 91
2 78
3 129
4 85
5 82
6 161
7 00
8 76
errors
227
234
235
422
Bob,
You have two problems:
(1) You have no refrigerant according to the pressure sensor. You can try bypassing the pressure sensor (you'll find instructions posted in the comments on the website) to rule out a faulty sensor. But most likely it's accurate.
(2) Your duovalve (heater control) is stuck open on the left side. You may notice that the air on the left is much warmer than the right. In most cases you can fix the problem by taking the valve apart and cleaning it. Google “w210 duovalve cleaning” and you'll find plenty of advice on how to do that.
Blake
Hi Blake,
Beer on the way via paypal!
1 – 98
2 – 82
3 – 100
4 – 100
5 – 143
6 – 145
7 – 06
8 – 85
Error Codes:
Eb1 – 419
Eb1 – 232
Eb1 – 234
Eb1 – 235
Eb1 – 419
Eb1 – 459
E – FF
Thanks in advance! Jack H.
Jack,
Thank you for the beer.
You have two issues going on.
#1: Your evaporator temperature sensor (#5) needs to be replaced. I've seen a lot of people with this problem in the last few weeks for some reason. The evaporator is not supposed to get colder than 32 degrees or else it can freeze and crack. The sensor exists to tell the A/C to shut off when the evaporator gets too cold. In your case, the sensor is reporting a temperature that is impossibly high (143 degrees). The air comes straight into the evaporator from the outside, so it really can't be any warmer than the ambient temperature. When the system recognizes that the evaporator temperature sensor can't be trusted, it shuts down the A/C to protect the evaporator from freezing.
#2: You have an error code for a faulty refrigerant pressure sensor (#7). Often this causes the EC light to permanently illuminate. Is yours lit? If so, you can bypass/override the refrigerant pressure sensor by doing the following:
1. Switch the ignition on (position 2).
2. Set the left temperature to 'HI' and the right temperature to 'LO'.
3. Switch the ignition off.
4. While holding the 'REST' button, switch the ignition on (position 2). On the left side, 'P1' will flash and on the right side, a code will be displayed.
5. Press the 'EC' button twice so that the left side flashes 'P2'.
6. Using the right side red temperature increase button, add 16 to the value.
7. Press the 'EC button again to store the updated code.
8. Turn the ignition off.
Sometimes the computer stores old error codes that appear spuriously. You can try clearing the codes and then rechecking them in a bit to see what problems are ongoing. Here's how you clear the codes:
1. Go into the error code mode as described in step 2 of the instructions on the website
2. Press and hold both AUTO buttons simultaneously for at least five seconds. The screen will switch to “e FF”
3. Shut the ignition off.
So to recap, problem #1 is the evaporator temperature sensor. This definitely needs replacement. Problem #2 is the refrigerant pressure sensor, which usually can be overridden since there is a backup sensor in the compressor. It's possible that you need a recharge but I can't tell for sure until #1 and #2 are resolved.
A Google search should turn up instructions on how to replace either of those sensors.
Regards,
Blake Cameron
Hi Blake,
It's a 1999 E240, cold air will blow for the first 5 minutes and then it will blow what seems to be the air from outside. I think the air blows cold longer when I am driving on the freeway too. Below are the codes:
1 – 80
2 – 80
3 – 82
4 – 82
5 – 150
6 – 155
7 – 11
8 – 107
Eb1 – 234
E – FF
Beer should have been recieved from alexander a. or aurelialex. Thank you!