Good day everyone ! I have a 1996 W202 and the A/C compressor is not kicking in. The control panel seems to be working fine (temp. setting, air redirection, Auto, EC). The EC button is not on, meaning I can switch between AUTO and EC. I performed the diagnostics throught the ACC panel and got the following info with the engine off:

01 - 20'C
02 - 17'C
03 - 21'C
05 - 21'C
06 - 80.5'C
07 - LO
08 - 45 0
09 - 03
15 - LO
20 - 05
21 - 00'0
22 - 00'0
23 - 00'0
50 - 10'C
51 - 00
52 - 00

Where and what should I start looking at ? From the engine compartment, I can see that the compressor is freewheeling. The last thing that was done to the car by the dealership was replace the water pump 3 weeks ago. Is ther any posibility that something wasn't connected properly ? Any relays or fuses that I can check ?

Would greatly appreciate any help I can get. Thanks in advance !

Willy

Before trying to decipher these codes, you need to put on a manifold set and examine your system pressures. If the charge is low, then all sorts of errors will be trapped.

Good luck,

Thank you Larry for your reply.

Having read in other threads that the system has an automatic protection against low refrigerant pressure, that is the EC light will remain on the moment you start the car with no possibility of turning it off. So I assumed that low pressure was not the problem as the ACC unit works the way it should be except for the compressor not turning on. I'm suspecting that when the dealer replaced the water pump they might have accidentally disconnected something as it was working before the dealer worked on the car.

Anyway, I will have the pressure checked ASAP.

I had something quite similar on the 1997 C230. The AC worked great while moving at speed on the open road. However, once I got into town and slowed down, the AC compressor shut off. They system was still on and appeared fully functional. The problem was it blew only warm air.

The problem turned out to be a blown relay that controls the auxiliary cooling fan. Without the auxiliary cooling fan running and no air moving around, the compressor would shut off. I couldn't figure out the problem myself, but my mechanic figured it out pretty easily. It's worked perfectly ever since.

The relay in question isn't one of the normal ones you'd find in the fuse box area. Rather, it was somewhere in the cooling fan area under the front of the car.

I'd have to dig up the receipt to get the part number, but it was about $100 USD.

Best of luck.

__________________
Michael

1988 300 SL (5 Speed)
1994 E320 Wagon
1997 C230

Michael, thanks for the reply. And I had the same problem with my 190E, but the aux fan causing the compressor to shut off only happens when the engine temp is up (could be wrong). But in this case, whether at speed or idle or on the first start of the day, the compressor will not kick in, can't even hear the tick of the magnetic clutch which leads me to suspect some electrical issues.

Willy

Those sensor codes are useless. You MUST read them with the engine running and the ACC system operational.

The EC light is on and the compressor is off because the system is in protection mode. If the compressor were to engage with low coolant, the lack of lubrication will destroy it.

Odds are you have either lost your coolant through a leak or your evaporator temperature sensor is bad. The ACC system stores it's own codes in the panel as well as the real-time sensor data. I can't recall the keying sequence...

__________________
John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

John, thanks for your reply. In the case of my car, the EC list is not on, in fact I can switch to AUTO, EC, recycle mode through the ACC panel, but the compressor will not engage.

The first step in troubleshooting this problem is to connect gauges and ENSURE that the system has an adequate charge. THEN you can take the next step.

Best of luck,

Actually the actual values give lots of info even when a post does not. For example I can tell from the codes that the car is a before 1996 model (a piece of required info that would be nice).

I can also tell that it is version coded as a 220 with a centigrade display. IS THAT WHAT YOU HAVE and want version 06 on line 20 would be 111 motor with "F" display. If you have any other motor that is the problem and I have seen it atleast three times in 202 chassis.

If 07 says LO I would guess you are low in refrigerant as that is high side pressure, usually in bar.

Position 8 tells me that the blower is running near hi speed.

The first four numbers tell me its hotter in the car than outside even with the engine at operating temp as shown in pid 6.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Steve, if the car's engine is not running, wouldn't the pressure value be "off" since the compressor is not running? Or does it measure the static pressure? Is like a high-side gauge, or does it measure the working of the compressor?

Uh, ummm. If it's a high-side gauge, then I suppose the system should still be pressurized even with the engine off?

I think I'll have a look at my own car this morning.

Thanks for all the info on the info. Can you enlighten us as to some of the version info you gleaned?

__________________
John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

Nothing beats intimate system familiarity such as Steve has.

Good luck,

Gentlemen, my apologies for the lack of info about my car in the original post. It is a 1995 (December) W202 C200 (as I am in Europe, Rome to be precise), stick shift with 59K miles, and yes the temp settings and displays are in centigrade.

I will be taking the car back to the dealership, thought that it's better to be a informed before I do so.

Steve, from the readings you suggest that the car might be low in refrigerant, could that be the reason why the compressor is not kicking in ? Strange, because the EC light in the ACC panel never stayed on.

Once again, thanks to everyone's response, greatly appreciated.

Willy

undefinedThe dealer finally found and fixed the problem. They replaced the condenser due to leak. It's been over 3 weeks and so far so good. (fingers crossed)

Not really sure if this is a related topic, but somehow I started hearing loud sqeaking noise coming from behind the dash between the center console and passenger side. Not sure if I should call it a squeaking sound as it sounds more like metal to metal with some sort of spring action behind it. It only happens when I release the gas pedal to change gears with the A/C off. It doesn't make the noise with the A/C on, or in EC mode, as long as the blower is on which also means one of the air flaps is open. My initial suspect was the blower motor, but after taking off the panels etc, I can verify that everything is tight in there. Could it be one of the flaps in the air distribution system or the heater solenoid valves ? I have removed the glove compartment, lower panel in the passenger side, charcoal filter, blower cover, the only thing left are the passenger airbag and air distribution system. It's driving me crazy. Would really appreciate any help from the list. Thanks in advance.

Willy

BTW the car is a 96 W202, stick shift w/ automatic climate contol.

How do you perform diagnostics through the ac panel?