Mercedes-Benz Forum banner

1 - 4 of 4 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
so i have had my S class 2002 for the summer so far and 0 issues with the aircon, but now when the temperature is dropping im finidng myself having issues

so to go in to detail
when im trying to warm up the car the middle air vent is not on whatsoever (its turned to auto) and the ones in the door is "barly" puting out ANY air at all but they at least are, the defrost vent in the front works and not works at the same time, its the only vent showing air in to the cabin, but its shooting COLD air!!!! also if i turn off auto on the centre airvents in the front they turn on like normal but they are just like the window vent shooting COLD air
this is a problem as long as the system is set to a higher temperature than there is inside aka its supposed to heat. is the temperature is set to less than the outside temperature the aircon turns on and all the vents start up no problem but its still cold as the temperature is set to cold.
meanwhile i have the long wheelbase version and a independent system in the rear and those 2 in the centre for the rear seats is like a tornado of WARM air, in other words the rear vents works flawlessly without any issue
any help with this would be much appriciated

(by cold air i mean like same temperature as outside or maybe 1 degree celsius more but not noticable)
 

·
Registered
2003 S430
Joined
·
2,442 Posts
One common cause for different temp air from one side is the duo valve. This is a valve device that lives in the center between the two engine firewalls. There are two computer-controlled valves that manage the coolant flow to each side of the system, and a small 12vdc pump that increases coolant flow at low engine speeds, as well as operating the Residual Heat system to keep the car warm for a short time after parking.

The duo valve can be removed and carefully cleaned, and this will often fix the problem where one side will go hot when you need cooling, or cold when you need heat. There are dozens of threads on how to do this repair, as well as quite a few YouTube videos.

There are numerous threads on this Forum on the Duovalve or Duo Valve, including this one:


Advanced Search in the W220 S Class section will get you more info...
 

·
Registered
Joined
·
7 Posts
Discussion Starter #3
One common cause for different temp air from one side is the duo valve. This is a valve device that lives in the center between the two engine firewalls. There are two computer-controlled valves that manage the coolant flow to each side of the system, and a small 12vdc pump that increases coolant flow at low engine speeds, as well as operating the Residual Heat system to keep the car warm for a short time after parking.

The duo valve can be removed and carefully cleaned, and this will often fix the problem where one side will go hot when you need cooling, or cold when you need heat. There are dozens of threads on how to do this repair, as well as quite a few YouTube videos.

There are numerous threads on this Forum on the Duovalve or Duo Valve, including this one:


Advanced Search in the W220 S Class section will get you more info...
the thing is front dont seem to get "any" heated air
and the rear is getting the heated air, front gets cold air, rear gets cold air
the only issue is COLD air coming in front when its supposed to be giving warm air, rear works just fine
the issue is not related from one side to the other side, its fron/back which is "supposed" to be pretty independent of each other as its 4 channel aircon in my car
 

·
Registered
2003 S430
Joined
·
2,442 Posts
The front duo valve controls the flow of hot coolant independently to both front sides, and, if installed, the rear duo valve controls the flow of hot coolant independently to both rear sides. If the front duo valve ceases to work on one side, one side is cold. If it ceases to work on both sides, both sides are cold. Each of the four quadrants are controlled independently - which says nothing about whether it is possible for both sides of either valve to fail at the same time.
 
1 - 4 of 4 Posts
Top