W140 climate control -- red & blue buttons

[diesel dawg]

Can someone please tell me what these little red and blue buttons located at the center vents are for?

I assume that the blue one is for cool and red for hot. But how and when to use them?

Is the blue one to be used only when the A/C is on?

If the A/C isn't one, and you press the blue button, does that cause the compressor to kick on?

Just how are they intended to be used? Are they useful?

The manual isn't very helpful.

Thanks,

DieselDawg

[pbrennan10]

they make air come out the front vents.

[diesel dawg]

Not really sure if I should say "thanks" for that reply!

Seriously, I would like to know how these buttons are designed to be used.

I haven't noticed any change of air flow associated when activating these buttons.

I believe that the little wheel knobs are what increase or decrease the air flow through the various vents.

Oh what the hell, thanks for the reply, but a little more detail would be nice.

[rchase]

Originally Posted by buckwheat

The red one routes any heat that has been demanded by the system to the upper vents. Accordingly, the blue routes any cooling to just the two center vents and dash side vents.

From what I can gather, it closes all vent flaps except the center two flap valves, so runs cool/heat into either depending on which one is pushed. So it should close floor and defrost vents, but leaves the rear vent alone. Note that if the system is not calling for any kind of heat, it will route air up there but no heat. Same with cool.

Why? To me it's handy when it's hot or cold, and I want cool/heat air out of those vents only - instead of the system's idead of routing air all over the car as it wants.

Interestingly, when a/c kicks in and it figures out that it's really hot inside the car, it's hot outside the car, and the a/c is producing cold air, it will do this anyway - close floor and defrost and route to center/outside.

Press the cool (blue) button next time it's really hot and you'll see what I'm talking about.

Hope this helps -

I read that in the manual. I like the buttons because I tell my passengers that its an "I am cold/I am hot" button" to bypass the car's thermostat. That way they dont set the thermostat all the way cold or all the way hot to compensate for their preference. Even though just by pressing both buttons you can get it back to 72 degrees it just annoys the hell out of me to have passengers who don't know the car screwing with the rather complex climate control.. Most of them buy it.

[Brett San Diego]

Another result of pressing one of these buttons is that you get the option of choosing air flow from the center vent when in manual mode. If you press the button with the seated figure with arrows pointing toward the person, this switches the climate control over to manual mode, and you can select fan speed and air flow direction manually. Press the button repeatedly, and you cycle through the combinations of vent selections, but unless you press the blue or red button in the center vent, you will never see the arrow pointing at the face of the figure light up, and you will never get air flow from the center vents. It took me a long time to figure out how to get air from those damn vents manually. You've got to have the red or blue button lit up on the center vent. This is NOT mentioned anywhere in the manual.

In automatic mode, the buttons simply direct more air flow from the center vents. But, I haven't done a full test to see exactly what the temperature of the air from the center vent is in relation to the air coming from the rest of the system.

Brett

[Peter Guenther]

My manual on the 92 500SEL states that pushing the blue makes the air coming out of the center vent cooler, red makes it warmer. It kinda works I think.