This is the climate control diagnostic menu.

The first thing you see is the interior temperature.

Basically these are used to check the function of various sensors connected to the system.

 

I know this is the process for diagnosing early w202 climate control issues:
SELF-DIAGNOSTICS
DIAGNOSTIC TROUBLE CODE READOUT
Entering Diagnostic Trouble Code (DTC) Display Mode
1) Turn ignition on. Press down arrow push button until "LO" is shown in A/C-heater control panel temperature display window.
2) Within 20 seconds, simultaneously press REST and defrost push buttons for more than 2 seconds. The Light Emitting Diode (LED) in the recirculated air push button will blink and the display window will show "di R".3) Press AUTO push button repeatedly, recording each DTC,until all DTCs are displayed. Permanent malfunctions are displayed first. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION tables.
4) If no permanent malfunctions are stored, the display window shows "En d". Press AUTO push button again. Intermittent DTCs will be displayed. Intermittent malfunctions are recognizable by the degree (°) symbol displayed along with the DTC (example: "04 °").
5) If no intermittent malfunctions are stored, the display window shows "En° d". Proceed to ERASING DIAGNOSTIC TROUBLE CODES.

Erasing Diagnostic Trouble Codes
1) After display window shows "En° d", press AUTO push button once again. Display window should show "dE L" (delete).
2) To erase DTCs, simultaneously press down and up arrow push buttons for more than 5 seconds. The display window should show "- --". If not erasing DTCs, press the AUTO push button. The permanent DTCs will again be displayed. Proceed to EXITING DTC DISPLAY MODE.
Exiting DTC Display Mode
Simultaneously press down and up arrow push buttons until the pre-selected temperature setting of "72 °F" is displayed. Turn ignition off.
DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION TABLE
----------------------------------------------------------------------
Code(s) (1) Cause
01 ......................Normal
02 ......................A/C-Heater Control Panel
03 & 04 ..............In-Car Temp. Sensor/Blower Short Circuit
05 & 06 ..............In-Car Temp. Sensor/Blower Short/Open Circuit
07 & 08 ..............Outside Temp. Sensor Short Circuit
09 & 10 ..............Outside Temp. Sensor Short/Open Circuit
11 & 12 ..............Heater Core Temp. Sensor Short Circuit
13 & 14 ..............Heater Core Temp. Sensor Short/Open Circuit
19 & 20 ..............Evaporator Temp. Sensor Short Circuit
21 & 22 ..............Evaporator Temp. Sensor Short/Open Circuit
23 & 24 ..............Engine Coolant Temp. Sensor Short Circuit
25 & 26 ............. Engine Coolant Temp. Sensor Short/Open Circuit
27 & 28 ..............Refrigerant Pressure Sensor Short Circuit
29 & 30 ............. Refrigerant Pressure Sensor Short/Open Circuit
31 ......................A/C Compressor RPM Sensor Circuit
32 ......................Drive Belt Slip Recognition Circuit
47 & 48 ...............Auxiliary Coolant Pump Short Circuit
49 & 50 ...............Auxiliary Coolant Pump Short/Open Circuit
51 & 52 ...............Duovalve Short/Open Circuit
53 & 54 ...............Duovalve Short/Open Circuit
59 & 60 ...............A/C Compressor Clutch Circuit
61 & 62 ...............A/C Compressor Clutch Short/Open Circuit
63 & 64 ...............(2) Auxiliary Fan Activation Short Circuit
65 & 66 ...............(2) Auxiliary Fan Activation Short/Open Circuit
67 & 68 ...............(3) Auxiliary Fan Activation Short Circuit
69 & 70 ...............(3) Auxiliary Fan Activation Short/Open Circuit
(1) - Other than codes 01 and 02, the even numbered codes indicate an intermittent malfunction.
(2) - Auxiliary (condenser) fan stage 1 (low speed).
(3) - Auxiliary (condenser) fan stage 2 (high speed).
----------------------------------------------------------------------
DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION TABLE
----------------------------------------------------------------------
Code(s) (1) Cause
71 & 72 ....Closed Throttle Speed Increase Short/Open Circuit
73 & 74 ....Closed Throttle Speed Increase Short Circuit
75 & 76 ....Diverter Flap Switchover Valve
77 & 78 ....Diverter Flap Switchover Valve Short/Open Circuit
79 & 80 ....Tempering Flap Switchover Valve
81 & 82 ....Tempering Flap Switchover Valve Short/Open Circuit
83 & 84 ....(2) Fresh/Recirculated Air Flap Switchover Valve
85 & 86 ....(2) Fresh/Recirculated Air Flap Switchover Valve Short/Open Circuit
87 & 88 ....(3) Fresh/Recirculated Air Flap Switchover Valve
89 & 90 ....(3) Fresh/Recirculated Air Flap Switchover Valve Short/Open Circuit
91 & 92 ....(2) Defroster Flap Switchover Valve
93 & 94 ....(2) Defroster Flap Switchover Valve Short/Open Circuit
95 & 96 ....(3) Defroster Flap Switchover Valve
97 & 98 ....(3) Defroster Flap Switchover Valve Short/Open Circuit
99 & 100 ...(2) Footwell Flap Switchover Valve
101 & 102 ..(2) Footwell Flap Switchover Valve Short/Open Circuit
103 & 104 ..(3) Footwell Flap Switchover Valve
105 & 106 ..(3) Footwell Flap Switchover Valve Short/Open Circuit

(1) - Even numbered codes indicate an intermittent malfunction.
(2) - Long (80 percent movement) stroke.
(3) - Short (20 percent movement) stroke.
----------------------------------------------------------------------

READING SENSOR VALUES
1) Turn ignition on. Simultaneously press down and up arrow push buttons until the pre-selected temperature setting of "72 °F" is displayed. Press the AUTO push button.
2) Press REST push button for more than 6 seconds. The display window will alternately show "01" and an in-car temperature of "72 °F", or "LO" if there is an open circuit, or "HI" if there is a short circuit.
3) By pressing the windshield air distribution push button, the next ascending test step is displayed. By pressing the footwell air distribution push button, the next descending test step is displayed. See SENSOR VALUE DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table. Press REST push button to exit reading sensor values mode.

SENSOR VALUE DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION
------------------------------------------------------------
Code Cause/Value
01 ............................. In-Car Temperature Sensor
02 ............................ Outside Temperature Sensor
03 ........................ Heater Core Temperature Sensor
05 .................... Evaporator Core Temperature Sensor
06 ................. (1) Engine Coolant Temperature Sensor
07 .............................. (2) Refrigerant Pressure
08 ............................ (3) Blower Control Voltage
09 .......... Software Status Of A/C-Heater Control Module
15 ........................... Selected In-Car Temperature
20 ................................. Software Version Code
21 ...................................... (4) Engine Speed
22 .............................. (5) A/C Compressor Speed
23 ......................................... Vehicle Speed
50 ................................ 80.° - 00.° (Not Used)
51 ......... Number Of Actual Drive Belt Slip Recognitions
52 ......... Number Of Actual Drive Belt Slip Recognitions
(1) - A display of "12.°5" corresponds to 125 Celsius (257°F).
(2) - Refrigerant pressure is displayed in bar. One bar equals 14.5037 psi. A display of "12.°8" corresponds to 12.8 bar (185.6 psi).
(3) - A display of "16.°5" corresponds to 1.65 volts.
(4) - A display of "06.°0" to "70.°0" corresponds to 600 RPM to 7000 RPM respectively.
(5) - A display of "00.°0" to "84.°0" corresponds to 0 RPM to 8400 RPM respectively.
------------------------------------------------------------


For clarification this is for this model A/C Pushbutton Unit

 

I tried the procedure yesterday. But I did not see "di R" displayed after I pressed the "reset" and the "defrost" buttons (nor did the LED in recirculate air blink). But the display did alternate between 01 (normal?) and a temperature reading (what's that? reading from inside temperature sensor, since the temp is set at "lo"?). So it is working somewhat. I just don't know why it is different. Is it because I have a different year/model (1995 C220)?

 

What you got is the sensor readings. The way to cycle those is by pressing "By pressing the windshield air distribution push button (top left button of control unit), the next ascending test step is displayed. By pressing the footwell air distribution push button (bottom right of control unit), the next descending test step is displayed"

To get the trouble codes. Turn key to on (don't start), hit your auto button, set temp to low "lo", press "0" (turn off), press auto (again) and within twenty seconds, press "rest" and defrost button at the same time. Within two to three seconds the fan should shut off and the recirc light should be flashing with the "dlr" in the display. Follow the directions above for cycling and deleting. Michael

 

To get the trouble codes. Turn key to on (don't start), hit your auto button, set temp to low "lo", press "0" (turn off), press auto (again) and within twenty seconds, press "rest" and defrost button at the same time. Within two to three seconds the fan should shut off and the recirc light should be flashing with the "dlr" in the display. Follow the directions above for cycling and deleting. Michael

I think what I missed was "press "0" (turn off) and press auto (again)." It was not in the first instruction. I will try it again tonoght!

 

I find by pressing 0 assures the display will come on. Whereas, in the original instructions it only works some of the time - YMMV. Good luck. I have pulled the codes and still can't get my A/C to work. So, it is only part of your diagnosis/fix. Michael

 

No luck, I tried it again, and I still got the sensor reading. You are right about pressing top left and bottom right buttons of the control unit, it did cycle through a bunch of codes that I don't quite understand (where can I find those info?). But I just could not pull up the DTC.

My AC is working fine now.

 

The codes are posted above and below:
01 ............................. In-Car Temperature Sensor
02 ............................ Outside Temperature Sensor
03 ........................ Heater Core Temperature Sensor
05 .................... Evaporator Core Temperature Sensor
06 ................. (1) Engine Coolant Temperature Sensor
07 .............................. (2) Refrigerant Pressure
08 ............................ (3) Blower Control Voltage
09 .......... Software Status Of A/C-Heater Control Module
15 ........................... Selected In-Car Temperature
20 ................................. Software Version Code
21 ...................................... (4) Engine Speed
22 .............................. (5) A/C Compressor Speed
23 ......................................... Vehicle Speed
50 ................................ 80.° - 00.° (Not Used)
51 ......... Number Of Actual Drive Belt Slip Recognitions
52 ......... Number Of Actual Drive Belt Slip Recognitions
(1) - A display of "12.°5" corresponds to 125 Celsius (257°F).
(2) - Refrigerant pressure is displayed in bar. One bar equals 14.5037 psi. A display of "12.°8" corresponds to 12.8 bar (185.6 psi).
(3) - A display of "16.°5" corresponds to 1.65 volts.
(4) - A display of "06.°0" to "70.°0" corresponds to 600 RPM to 7000 RPM respectively.
(5) - A display of "00.°0" to "84.°0" corresponds to 0 RPM to 8400 RPM respectively.

 

Thank you! I didn't realize they were already included in your previous post.

 

I am glad you got your AC working. What do you think made it start working?

 

I have no idea.

For the last 2-3 years, I have to charge my refrigerant once a year. Charge it in the spring and it will last the whole season; but come next spring, I would not have A/C and would need to recharge again.

They have put in leak detector, but cannot find any leak. So they speculated it is probably leaking inside the car under the dash. And since it is too costly to rip open the dash to repair such a small leak (which they are not even sure is there) for an old car, it is more practical to just charge it once a year.

But the other day, my A/C suddenly stopped working (blowing hot air). This is kind of surprising because the charge is supposed to last for the whole season, unless the leak is getting worse. The next day, the A/C started working again, and works fine since. I checked the pressure on the A/C, it was in the green zone. So I have no idea what happened and that is why I was thinking maybe I could pull the DTC to see what had happened. Well, you know the rest.

 

I got a whole bunch of errors. Some of them are not in the chart posted above. Can someone tell me what they mean?

The error codes are:
23°3, 42°6, 41°9, 42°1, 42°2, 45°1, 45°2, 45°5, 45°6, 45°7, 45°8

Thanks in advance. I love my C220 and I want to keep it running nicely.

 

i have gotten some weird codes too
41°6 41°7 41°9
i have no clue what this means though

 

My A/C is not cold, so I tried the diagnostic procedure, and all I can bring up is 01 (normal?), and a temperature reading (alternating between the two automatically).

The LED in recirculate air push button never blinked and the display never showed "diR".

I wonder if it is because my car ('95) is built before they started this diagnostics procedure.

 

bump

 

Any help appreciated:
I get cold A/C for about 3 minutes when I start up the car, then ambient air. The compressor seems to be kicking out after a few minutes. The pipe near the recharge port is ice cold at first, then warms up. I recently cleaned the douvalve and had great results for about 2 weeks!

Diagnostic Test Codes:
23*3, 41*6, 41*7, 41*9, 45*1, 45*3, 45*4, 45*7, 45*8

Sensor Readings (engine idling):
01 - 86 F
02 - 102 F
03 - 80 F
05 - 155
06 - 192
07 - 15*4
08 - 122
09 - 44 F
10 - 125
20 - 05*0 (a few minutes later 0)
21 - 060
22 - 000
23 - 000
24 - 13.9
40 - 03
41 - 03
42 - 26
43 - 6-C
50 - 62 F
51 - 72 F
52 - 50 F
54 - OFF


Any ideas?

 

Hi,

I'm curious does this diagnosis method not work for 1995 C280?

No luck here!

 

I dunno

 

Hey, my sensor reading #9 shows 02 for software ver. There is a service bulletin due to problems of erratic airflow through the center console vents. Its suppose to upgrade to newer version to fix it. Anyone show a different version # or have updated their version and it was fixed, supposedly your service center will attach a sticker near emissions sticker inside hood showing update? I'm still researching this.

 

I went in to pull all active recalls and service bulletins for my car at the dealership a month ago. Everything is closed and no new bulletins are open for my car. Would you happen to know the bulletin number? I am interested because I have that erratic blower problem myself. Any further information will be very much appreciated.

 

Display unit change

Friends,
hi, my cars AC unit was displaying temp in F. The AC went off a week ago and when I was trying to press its buttons randomly, it came back but with Celsius. I don't know which buttons I have pressed. Can you please help ? Thanks!