W203 air conditioning diagnostic mode (C320/C32 only)
 

Push "0" and "EC/REST" button simultaneously until display changes (approx. 5 seconds)

I've only included the values that may be of interest to owners

00: Interior temp sensor
01: Interior temp sensor
02: Ambient temp sensor
05: Evaporator temp. sensor
06: Engine coolant temp.
07: refrigerant pressure
08: refrigerant temp.
16: carbon monoxide value
17: nitrogen oxide value
18: dewpoint temp.
21: engine RPM
22: vehicle speed
24: battery voltage (very handy)

woah... thats kewL!

I don't get it -- you hold the buttons and these codes pop up on the display or what ? or if certain codes pop up there's a prob or what?

16: carbon monoxide value
17: nitrogen oxide value

I wonder what it does with these values? Are they cabin readings or outside air readings?

I wonder if the car will shut itself off if the cabin CO levels get too high in order to save the occupant's life? Now, THAT would be something, wouldn't it?

Used to have those on my audi a4 :mad: but oh well. does these only show on c320/C32 or anyone with digital climatronic?

Thanks Dave!!

I tried it today, but I only get a blinking of "00" on the left side, and "21" on the right side. How do you actually do the reading? Thx

It's possible that some of those sensors may not be in cars that have been retro-fitted with climatronic, although I think it should still work for some measurements.

My guess is that the 00/21 shows that it was 21 degress Celcius inside of your car (it's German so I bet the values are metric).

- BT

OO and 51 here.
After experimenting I found that when I pushed in on the drivers side rotary knob it would change states. I tried to get the info for all the codes from my dealer. He showed me the book and guess what. Your right - go to DAS.
I loved the look on his face when I asked for this info. Kinda like - WTF.:D

There was a thread about a year ago on same topic.

Actually, you don't need to hold the 0 button. Just hold EC button for 5 seconds and the display will show 00 code. Press the left Auto button to move up the chain (00, 01, 02), and right button to move down. The code and value will alternate on the left and right end of the display. When showing RPM, it is in 10s. So a value of 153 means 1530 rpm.

One point of note is the speedo on the dash (analog and digital) is intentionally set higher than the actual value by approx. 3%. This is done to give the driver a margin of error when approaching posted speed limits. However, the car must know the "true" speed for various sensor inputs, like ESP. The digital AC display shows the true speed. You can try this by comparing the digital display true speed with the digital speedo in the dash. The difference is about 3%. So 60mph true speed is shown as 62mph in the dash.

Yes, the earlier thread I mentioned listed many more codes, but I can't remember what they are now.

for 2002
 

On 2002 C32 (digital A/C)
While the vehicle is on and the A/C is in operation, hold down the “REST” button for several seconds until the system goes into the A/C diagnostic mode.


On C32,
Pressing AUTO LEFT Side for 'up' and AUTO RIGHT Side for 'down'

On other C-class A/C,
Pressing “Air up' and 'Air down'
you can shift thru various a/c diagnostic registers.
Cycling through will show you the diagnostic register and its corresponding value.


Go to register 01 and make sure it reads what it should for inside air. BTW Mine is in F not C.

Then you are off to the races.

Oh, one more point of note. The diagnostic mode works with other MB models with digital display. For example, my 97 E-Class has the same feature. The codes are the same.

Just got to play with this secret sauce this morning. Gotta love secret sauce...:D

I noticed that some displays for temp read celsius, others read fahrenheit... but my speed reads in KPH. Need to play more.

QQQ, did your dealer provide you all the codes? Can you get them, please? Or is the list posted on one of the other forums? I don't recall this thread on this forum, but of course it could be present on others.

My display runs all the way up to measurement 61, then 62-?? read 00 to the right. I did notice that upon first entering this mode, if you "page down" (press right AUTO button) it starts with measurement value 99 and down, and some of these have values associated with them.

I have the complete list, although most of them aren't meaningful to non-technicians. Such things as auxiliary fan duty cycle readings, heater box flap percentage readings, hardware and software status, A/C compressor torque.

Well, Dave, can you share, anyway? Don't just tease us with half the story! Pretty please?

Re: W203 air conditioning diagnostic mode (C320/C32 only)
 

Ok, 22 produces a readout in kph , I think, because my analog speedo said 40 mph, my digital said 41 mph and this one here said 66. ????

Now, 24 produce a readout of 42. I know that 42 Volt systems are not yet in production cars. What gives?

MB-BOB: No, I didn't get this from dealer, but from this forum. Alas, it was a very antique thread dating back to 2001 and since purged.

amdeutsch: My car is Canadian and uses celsius / km/h. What you can do is go to the setting and change the digital display from mph to km/h, and F to C.

Those driving old E-Class, you should press Rest button, not EC.

Okay, okay, when I have more time I will. But I insist, the others are not very interesting.

Oh, so the climatronics diagnostic readout can be changed from the metric settings. Kinda like the FSS readout. Please tell us how.
Or were you refering to the fact that I should change my FSS readout to match the climatronics readout. ?????

In either case I don't believe that the voltage readout, setting 24, is going to be different between countries.
Overall what I was stating with my post was that there were inconsistencies with what you get versus what you might expect.

Hey, I tested this today on a new S-class. Worked like a charm, just held rest. I didn't have the list of what they meant though, so I just scrolled through a couple. The first 10 or 15 were all temperatures and they were in celsius.

You change the FSS to match climatronic.