W202 C220 Heating again!

Pjam27

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My C220 (no air con) is blowing hot air from all vents, nothing will allow cold air, even the central vent. I've dismantled the Duo Valve, all seems ok. Checked all fuses, no problems. Still hot air.
There is a menton of a pump? any ideas. Surely there must be a flap somewhere to allow cold air? is it easily accessable. Urgent help required it's hot here at the moment and I dont need a cabin full of more hot air. Thanks.
 

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The duo valve defaults in the hot mode, is there a voltage coming from the control unit, it is a pulsed voltage
 
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Pjam27

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Hi Malcolm,
Can you point me towards the control unit?
 

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Hi Malcolm,
Can you point me towards the control unit?

The control unit is the one in the car dash, that feeds the info to the valve,,you can measure the voltage whilst still plugged in, measuring unplugged is meaningless, it must be under load
 
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Pjam27

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Is there a diagram for this, do you mean the heater controls? or where in the dash is this control unit?
 

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Yes the output from the heater control is the one,it feeds the duo valve with the required voltage to close it
 
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Pjam27

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Sorry a bit confused, so there are the two dials, one for the Blower and one for the direction, i.e. window, feet, etc and then the 2 temperature controls, which am I looking at. thanks
 

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It is the temp controls that alters the output to the valves, one for each side, and one for each half of the valve
 
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Pjam27

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So I guess I need to strip the console to get at the components? is there a deatiled description of what I need to do anywhere?
Thanks
 

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The first check is on the plug that connects to the duo valve, and the voltages should be measured there
 
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Pjam27

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There is definitely power reaching the duo valve. having detemined that no matter what you do with temperature controls nothing changes. I understood the central vents should only blow cold air?
 

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no they blow hot or cold. or at least they did in my 202's and they do in my 210!
 
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Pjam27

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There is definitely power reaching the duo valve. having detemined that no matter what you do with temperature controls nothing changes. I understood the central vents should only blow cold air?
Surely with everything turned off It shouldn't be circulating hot air?
 

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If you have the pulsed voltage when the connector is plugged in and its under load, then with the controls set to the min temp the heater should blow cold air, if it does not then the Duo valve is not working
 
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Pjam27

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When you state "under load" do you mean with the blower operating?
 

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No, nothing to do with the blower, I mean with the plug from the control unit plugged into the duo valve
 

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no they blow hot or cold. or at least they did in my 202's and they do in my 210!

that was the case in my car before the dealershiped fixed the diaphrams, i told them abdout is but they said it was designed to always blow cold air, any help i would appreciate it.

Thanks
 


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