Why would one A/C vent blow cold and not the others?
The center/passenger side a/c vent blows cold air and the passenger outside vent does a little. When I set the thermostat on the same temperature for the drivers side it blows hot/regular air.
RE: Why would one A/C vent blow cold and not the others?
My 98 E320 is currently in the shop for the same problem. With the A/C on, the passenger vent and the right side vent of the center register blow cold air. The driver's side vent and left vent of the center register blow ambient air.
The problem appears to be a flap that regulates the mixing of ambient air & air conditioned air. The climate control modulates the temperature in the two zones by adjusting this mix.
I believe it's normal for the center vents to blow more air than the outer vents when the A/C is on.
RE: Why would one A/C vent blow cold and not the others?
As far as I know the center vents always blows cold air at least it does in my car (E220 cdi -99), but my car also jerks around and sometimes blows warm air but that is only done in either the right or left sidevents.
The problem is located to the duovalves as previous post says, but I haven't tried to lubricate it yet!
In your case I doubt it is the duovalves but it's easy to check so why not. If you doesn't want to lubricate just clamp both water lines instead.
If you would like to check out temp and pressure sensors and other stuff to try and examine the AC system, check the link below:
RE: Why would one A/C vent blow cold and not the others?
the valves are located in the engine bay on the right side near the strut tower.
Item 68 on the picture.
There are a couple of torx screws that hold the metal cover on, remove that and you'll see what to do. lube with vaseline if you have any, it's water resistant.
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