My 2000 CLK320 coupe recently had the check engine light go off. The MAS was replaced under warranty.

Ever since, the air conditioning has been acting up. After being parked overnight or for 8 hours at work, the vents only blow uncooled air out! Even at the lowest setting, no cold air comes out. This is true even if the car is driven for 30 minutes.

However, if I drive for 10 minutes, stop and go get groceries (for example), and then restart the car, the air conditioning will blast cold air at me. I did the diagnostic and came up with these values (air conditioning was working at the time)

1 (in car temp) 28
2 (outside temp) 30
3 (heater core temp L) 16
4 (heater core temp R) 15
5 (evaporator core temp) 5
6 (engine coolant temp) 88
7 (refrigerant pressure) 4
8 (refrigerant temp) 35
9 (not used) 0
10 (blower control voltage) 1.2
20 (control current of aux fan) 0
21 (engine RPM) 7
22 (vehicle speed) 0
23 (terminal 58d battery charge) 0
24 (battery voltage) 14.0
40 (software status register) 8
41 (hardware status register) 5
42 (???) 232
43 (???) 30

Then I repeated the diagnostic when the A/C was malfunctioning. The Evap Temp Sensor said 19 and wouldn't get any lower while the fan just blew warm air at me. Then after 15 mintues, suddenly the A/C turned on, blasted freezing cold air, and then the sensor said 3!!!

So I got the Evap Temp sensor replaced but it didn't fix the problem. The OBDII diagnostic yielded the following error codes:
B1234: Sun Sensor
B1421: Cycle Module

HELP!?!?! I understand that you can ignore the sun sensor error code, but I can't find much about the cycle module on these forums.

AEmgee,

I have a volvo with a sun sensor. I beleive its job is to step up the auto setting to a colder temp if the sun is out and offset the other way at night. Could be a possibility.

Ron

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I love my Mercedes

Just a t thought, I was had a clk with same problem. Searched everywhere even put in a new evap sensor. Turned out car had the compresor wire to be slowly breaking away from the compresor connector. this was caused by bad motor mounts. I just rembered that, wanted to share some info.

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Ok, my car is really $(#%ed today...

The auxiliary fan is blowing all the time now when the car is running! I suspect that the cycle module needs to be replaced.

In addition, on the climate control screen, when I select "Auto", the fan speed indicator disappears! This never happened before, so I don't know what's going on...

Anybody have thoughts about this?

Just an update on this...

Turned out it was a faulty pressure switch. After replacing, the climate control is working beautifully again.