tbrown

I have a new 2004 E500 4 matic and the A/C does not come on, the A/C light is always on. I push the A/C -Rest button and it blinks and then stays on, I guess a service visit. After fooling around with the buttons, I did find if you hold the REST button down for 10 seconds a new screen displays with numbers on the left and degrees on the right, you can change the left and right with the temperature keys, does anyone know what they do ? Also if you have a window open and hold down the Recirulate button the windows close. Neat !

JimPurdy

The "AC" light should be off. The AC light comes on when you press the AC button to indicate that you have taken the system out of "Auto" mode and have turned off the AC. You can press the Auto button and the AC light should go out and the AC should come on.

DaveFr

You have the standard four zone AC system and, assuming it hasn't changed from the 2003 system, here is the way I think it works.

If you push one of the auto buttons on each side of the AC display, the red light in both buttons will come on. The word "Auto" will appear in the display. The AC system will now control fan speed, temperature (whatever temperature you've set for each zone) and air distribution automatically for both the AC and the heater.

If you now manually increase or decrease the fan speed, the word "Auto" will disappear from the display. Air distribution and temperature will still be controlled automatically for both the AC and the heater. The fan speed will remain at whatever speed you selected.

If you now press the "AC Off/Rest" button, you will only have the heater online and the temperature will be controlled automatically.

Finally, if you rotate the dial around one or both of the auto buttons, you will go into manual mode which gives you manual control over fan speed and air distribution. The system still controls the temperature in each zone automatically.

To test whether your AC system is working properly, put the system in full auto mode by pressing one of the Auto buttons on each side of the display. Then turn the temperature in one of the zones down as low as it will go. Assuming the temperature in the car is higher than the temperature you just set, the AC should come on. If it doesn't, take the car in for servicing.

When you press the AC Off/Rest button for more than five seconds you access the climate control system's diagnostic section which displays various values helpful in diagnosing problems. If you seach this forum, you can find an explanation of the various codes.

Finally, the feature you discovered when you hold in the Recirc button is actually better than you discovered. First, both the Recirc and the Charcoal filer buttons work the same. Second, say you're driving along with some windows and the sunroof partially open. You approach a dusty area and push the recirc button to close the sunroof and the windows. When you leave the dusty area, if you push the Recirc button (or the Charcoal Filter button) again, the windows and the sunroof will return to the exact positions they were in previously.

GL with your new car. Despite some problems, it's a great car.

OPM Inc.

I'm still trying to figure out how to get the air to come out from the middle ducts.

norb

If you want air out of the middle ducts, turn the knobs around the Auto Button, to where the icon with the arrow pointing straight at the little man.

Consult the manual for more details.

Silvergt02

I have a question about the AC. Why is the middle knob blue and every other one red?

kjlr144

I have searched the forums for an explanation of what happens when you hold down the AC Off/Rest button for more than 5 seconds but have been unable to locate the thread that discusses this. Can anybody help?

__________________
2004 E320 4-Matic Capri Blue/Ash, Appearance and Premium Packages, 4 Zone Climate Control

DaCeptak0n

Why has Mercedes made everything in the car so easy to use, simply at a touch of a button like the rear sunshade or droppoing of rear headrests yet made the A/C and heat controls (for those without the 4 zone climatic control) so hard to figure out!!!???

HELL ONA HARLEY

This blue knob controls the "cool" air from the center vent... It will allways supply cool air, this is why its blue... In the winter when your heating the cabin for warmth, this vent will blow cool air on your face to keep you refreshed (european feature). Simply turn the knob to controll volume....

marksatex

The cool air feature is really a nice touch on long drives in the winter.

I just wish on the 4-Zone- you could control the rear fanspeed.

awiner

See:

https://mbworld.org/forums/showthrea...highlight=REST


For an explanation of the A/C Diagnostic mode using the REST button.

You problem sounds like a bad evap sensor or something.

10000_lakes

I have 2004 320 4matic, same exact scenario. The AC off light was always on. Push the AC button to turn it on (the light should go off), and the light just flashed several times, then stayed on. Perplexed, I went to the dealer to ask them if I was doing something wrong. No, there was a problem, and in about an hour, they fixed it via a software solution. Other than this, I too have had a fairly trouble free experience and truly enjoy this car.