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Air Conditioning Codes and Recharge Info - Clearing Codes

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On my last road trip my AC compressor shut down (2000 W210 – E55) and the EC light became stuck in the on position. I searched many threads and even spoke to my local Indy Benz tech who told me I would have to bring the car to a MB tech who can clear the codes. Many posts I found confirmed this, saying you can’t clear the codes without hooking up to the DAS/STAR system. This in fact is NOT true.

After reading my codes I realized the system shut off the compressor due to low refrigerant pressure. When refrigerant pressure reaches about 8-7 bar or lower the compressor automatically shuts itself down, therefore making it impossible to recharge since the compressor will not pull in 134a. Once I cleared codes (easily), I was able to hook up a can of 134a to the low side line and charge the system successfully. If you have the same problem and no leaks (or very slow) you should be able to rectify this with a $30 can of 134a and some simple button pushing. The following menus should help you diagnose what is wrong with your system. I am not a MB tech nor do I profess to be one so I need to throw in the disclaimer – proceed with caution and at your own risk. I have made every attempt to compile clear and accurate info to help anyone else out that has gone through the same issue I have or other AC issues.


Turn on ignition (run car)
Put both sides Temp settings at 72
Push and hold “REST” button till you get a 1 in the left side
Push the left “AUTO” button to scroll forward and right auto button to scroll back.
Let the car run 3 minutes before pulling data to ensure more accurate data
For AC diagnosis you only need to be concerned about codes 1 through 8

Code 1 = Inside Temp
Code 2 = Outside Temp
Code 3 = Left Core Temp
Code 4 = Right Core Temp
Code 6 = Coolant Temp
Code 7 = Refrigerant Pressure (This is the important one)
Code 8 = Refrigerant Temp


Switch ignition on
Set left AC/heater temperature control to HI
Set right AC/heater temperature to LO
Depress REST and EC switches simultaneously within 20 seconds of turning ignition on
Hold REST and EC switches for more than 5 seconds
Air recirculation lamp flashes
Depress right AUTO switch repeatedly. Note trouble codes
FF is not a code

What the codes mean:
003 B1226 In-car temperature sensor with blower
005 B1228 Heater output temperature sensor
006 B1229 " " "
007 B1230 AC evaporator temperature sensor
008 B1231 Engine coolant temperature (ECT) sensor
009 B1232 AC refrigerant pressure sensor
010 B1233 AC refrigerant temperature sensor
011 B1234 AC sunlight sensor
012 B1235 Heater intake air purity sensor
013 B1241 AC refrig pressure sensor, AC temp pressure sensor refrigerant level
014 B1416 Engine coolant pump motor
019 B1417 Engine coolant heater regulator valve LH
020 B1418 " " RH
021 B1419 AC compressor clutch
022 B1420 Idle speed increase
023 B1421 Engine coolant blower motor control module
024 B1422 Serial interface K1
025 B1423 AC heater valve block
026 B1424 AC heater air intake filter actuator
027 B1425 " "
029 B1429 Serial interface K2


In fault code mode press both “AUTO” switches simultaneously for more than 5 seconds (after last trouble code is displayed)
Once codes are cleared you will see display change to "d and FF"
Switch ignition OFF – All Codes are erased


Purchase a larger refill can of 134a with a gauge on it so you can read the low side pressure – helps as a guide to filling the system to the correct level. The instructions on the can will tell you what pressure to fill based on the ambient temp. You can find this refill can at any Walmart/Target/Auto Store for $20-$30. Make sure you purge the can before you fill:

Shake can
Squirt a very small amount of refrigerant to purge air out of the hose – you don’t want to introduce any air to your system.
Start car
Connect to low side port (drivers side left of engine mid bay with plastic black cap on it - unscrew)
Turn off EC button (light goes out and compressor goes on)
Read the PSI gauge on the can filler (should be low) around 20 psi or less
Pull trigger while gradually shaking the can and holding it upside down until it reaches instructed pressure depending on Ambient temp.
Once system is recharged it should be blowing cold air
Follow up by reading Code 7 – mine was originally 7 bar and became 17 bar after recharge. Also make note of the recharged bar pressure(17) – you can periodically check code 7 to make sure the system is holding the refrigerant pressure – if it decreases over time you have a slow leak and need to address it.

Hope this helps and good luck!
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'01 E320 15k miles..
32 Posts
DL - I would find a competent aircon shop for around $80 or less to evacuate the existing refrigerant, hold at vacuum to check for major leaks, then they will refill with 100% fresh refrigerant to restore the system.

Keep the beat !
Made it to the shop today. Took about 40 minutes on his scanner to clear the codes. The fan did not seem to want to kick on. Finally about 250-260 pressure. Seems a little high, 225ish would seem more common. 134 is weird stuff, and can give false readings. Anyways, I"ll see how far a re charge gets me , and if i have a slow leak or not. Nice to have some AC again since it was 99F here today..


'01 E320 15k miles..
32 Posts
I would recommend you post the current AC values in the W210 forum (rather than the AMG forum) and get feedback.

The other kind of-common problem, can be the evaporator sensor, which can give false readings to the system. Fortunately this sensor is relatively easy and affordable to replace.

I am not saying that could be a problem for you, post your current readings and let others comment.

Keep the beat !
I'm thinking you may be right. For value #5 I get 129, which I understand is a un plausible reading. I think it should be in the 40-50 range. Thanks for the tip. :thumbsup:

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