Strange aircon problem

[am8631]

ok - my ac blows nice and cold but my centre vents will ONLY blow cold! If i put the temp up the side vents blow nice and hot but the centre vents stay cold??

I took the duovalve out over the weekend to strip and clean but has not made any difference.

Does anyone know why my centre vents only blow cold?

cheers guys

Andy Mac

 

[lynall]

Pretty certain my centre vents only blow when temp cranked right down otherwise they dont seem to do much at all.
See here http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=202024&M=111%2E975&GA=722%2E605&GM=717%2E460&CT=F&cat=44V&SID=83&SGR=045&SGN=01
top pic is std air con next down is climate, std air con seems to be levers and cranks so maybe broken or gone out of adjustment, climate is all electric control see items 32,100,104,106 etc
Item 210 is central vent housing.



Lynall

 

[Brian WH]

Centre vents are Fresh Air from outside the car, not heated at all.

 

[am8631]

Well there you go! I didnt know that. Any body know what the thinking behind this setup was?

 

[Diesel Benz]

Centre vents are Fresh Air from outside the car, not heated at all.

Isn't that arrangement on older models only where fresh air bypassed even the cabin filter and was free air flow instead of forced air flow from the blower. Some had an on/off switch and fresh air switch. But as long as the centre nozzles blow cooled air, the air flow must come from the heater core, pass the evaporator and also the dust filter and the blower (wrong order, sorry). There is only a single path for all those components anyway.

The idea of cool air from the centre nozzles but no hot air is, as far as know, that cold air flows down and hot air flows up. Most of the cool air must come from the top nozzles to make the cabin comfortable and equally cool from roof to floor.

Hot air cannot be all lead to the floor because windows need to be kept open from moisture condensation. In order to have enough down to up hot air flow while maintaining visibility through windows, there is no room to blow hot air from the centre nozzles.