w202 Duo valve

[benzIT001]

Hi,
Unfortunately my c class is blowing out hot air on the passenger side regardless of temp setting. The Drivers side is ok (cold when set to cold and hot when set to hot).
I have done a search and want to know if i am right in thinking that this is a problem with the Duo Valve?

 

[Dec]

Could be an electrical connection issue at the heater controls or the valve electrical plug or perhaps the valve is sticking, try giving it a couple of taps with the handle of a screwdriver with the ignition switched on. I think the inner valve is the passenger side and the outer valve is the driver side.

http://www.mbclub.co.uk/forums/howto/26888-howto-clean-duovalve-w210.html


Dec

 

[benzIT001]

So i finally found the time to dismantle the duo valve. I inspected the pistons and these were moving pretty much freely so im not sure if the duo valve is at fault here? Are there any further checks I can carry out to find where the fault lies?

 

[Dec]

Fuses 2, 12 and 18 seem to be related to the heating, worth checking these out, other than that I wouldn’t be much use to you regarding any testing procedures.

Dec

 

[benzIT001]

Hi
just want to resurect this thread as I still have this issue.
So far I have swapped the heater control unit and the duo valve one at a time respectively. Each time I testing the heating and both of these have not resolved my issue. Admittedly I purchased the duo valve from a breakers who tested the part and confirmed it was working, surely I can't be unlucky enough to install another faulty part?

Any other suggestions on what could be the possible cause here?

 

[benzIT001]

Update
So I gatherd the reason why the duo value stops working is due to a break in connection in one/both of the coils so I tested my duo valve for and open circuit:-

As above it shows that both sides have continuity, i.e the duo valve is ok.

So since I have already checked the heater control unit my next guess is the interior temp sensors (passenger side) my be at fault. Can anyone advise me on where it is located so I can test it?

 

[benzIT001]

So after ruling out the Duop Valve I removed the interior temp sensor and inspected it. again i checked for continuity and it seems fine. Next thing I did was the check the wiring from the duo valve backwards and almost immediately I noticed that there was a burn on the protective wrap/tape that covers the loom. Unwrapping the tape to uncovered the broken/burn wire. I stripped the wire resoldered and everything is working again. Happy Days!