W211 A/C diagnosis

[GregMN]

2003 E320 W211
This is a friend's car. I am trying to figure out what the problem is with the A/C.
The "A/C Off" button's red light comes on. If you push the button the light flashes a few times then stays on.
The compressor pulley appears to be engaged. The center of the pulley is rotating.
The HVAC unit is set to auto with both temp. selectors set to 60 degrees.
Thinking it was low on refrigerant, I hooked up a fill hose that has a gauge on it and the gauge read 80psi. That seems high. The markings on the gauge face indicated that at the ambient temp (50 degrees) the pressure should have been around 25 psi.

Where to look next ?
I have found some mention of self diagnosis through the HVAC controls, but this car does not have the highline controls with the LCD screen.


Thanks,
Greg

[tjts1]

Does this car have an AC clutch? As far as I know the w203, w211 and all the MBs that came after have a clutchless AC compressor with a variable displacement controlled by a valve in the side of the compressor. The fact that the center of the pulley is still spinning doesn't exclude the possibility that the control valve has failed or if there's a problem in the climate control unit. You need to hook it up to a STAR or icarsoft scanner to figure out what's going on.

[GregMN]

Thanks. That is useful information. I will hook up the scanner the next time I get access to the car.

[jay_bob]

They seem to have taken away the live data ability on the W211 base (dual-zone) controls. The center display is just some icons and there are really no indicators to speak of except for the A/C, front and rear defroster, and the recirculate button.

Is your center display (where it shows Auto fan and Auto air direction) super dim? Mine is. I think it’s a Vacuum Fluorescent Display and these tend to get very dim with age. Mine is so bad I can only see it at night. Luckily I just leave it in Auto and don’t worry about it.

The premium A/C (4-zone) has numerical displays so it probably has some means of diagnosis.

I think they got rid of the integrated diagnosis feature when designing the W211 since the data is all available on the OBDII (unlike on the W210).

[jay_bob]

Originally Posted by jay_bob

They seem to have taken away the live data ability on the W211 base (dual-zone) controls. The center display is just some icons and there are really no indicators to speak of except for the A/C, front and rear defroster, and the recirculate button.

Is your center display (where it shows Auto fan and Auto air direction) super dim? Mine is. I think it’s a Vacuum Fluorescent Display and these tend to get very dim with age. Mine is so bad I can only see it at night. Luckily I just leave it in Auto and don’t worry about it.

The premium A/C (4-zone) has numerical displays so it probably has some means of diagnosis.

I think they got rid of the integrated diagnosis feature when designing the W211 since the data is all available on the OBDII (unlike on the W210).

On a W211 and newer, an off the shelf OBDII scanner with live data will read these parameters, you don’t need a Xentry machine.

[tjts1]

Originally Posted by jay_bob

On a W211 and newer, an off the shelf OBDII scanner with live data will read these parameters, you don’t need a Xentry machine.

Not any obd2 scanner. Icasoft is the only one I know of.

[jay_bob]

You’re right. I meant to say a scanner with live data capabilities, not any old dumb reader.

I was trying to say that the 211 have a fully functional OBDII port so you don’t need Xentry/HHT like you do in the W210 (which has the hobbled OBDII for engine only, and everything else goes through the 38 pin port).

[GregMN]

Finally got access to the car. Hooked up the scanner and cleared the A/C codes. The A/C off button went out and stayed out. I could not test the cooling output of the system because it was 42 degrees out.

It was 80 yesterday. So I called the owner and she said it worked great.