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[GermanXR2]

Guys I need your help with the heating/ventilation .... the Merc driving me crazy with that.

If I switch the heating control in the centre console to warm, warm air comes out of the vents in the centre console.

And only cold air comes out of the vents openings near the right and left doors.

I expect warm air, or i'm wrong?

[NEDREBEL]

The vents by the windows need to be closed on mine or else it blows outside air

[greywolf27030]

The vent near the door vents directly from the plenum under the windshield if it is open. Theoretically, when you close it and switch to heat it will blow warm air, but trust me it isn't very impressive...lol

[GermanXR2]

I check the Heating Defrosting S12-02 diagram and there are only two ducts (left/right) to the registers (vent).

From my understanding, if warm air cames out of the center console also warm air should come from the two vents near the doors, or?

[greywolf27030]

You're right, it should. But the amount of air isn't enought to help much.

[JJCapri]

agreed. could be a few things... those side vents have a lever up/down to switch from outside to inside air... lever may be disconnected, not touched, or stuck...

and the heater never really blows out of those very well. not sure if it's too far, heater blower motor just doesn't output enough, or what.. but very little air comes out, and depending how cold the outside air is, may not warm it up much.

or could be something with the duct work along the way. hose popped off, mouse chewed through so air blowing under dash instead, etc etc..

[greywolf27030]

Debris from the vent being exposed to the cowl duct can also cause it to not close properly.