Weak rear window demister (W220)

PJayUK

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Hi all

Quick one if I may..

The heated rear window (demister) is not very effective in my SClass, it seems to take ages to warm up and clear the rear screen. I also get the well known interferance on FM on my radio so I guess the rear window noise suppressor might be U/S.

A couple of questions....

Is there anything that could cause the heater to work less efficiently? My knowleadge of electronics suggests that as its a simple heating element it should either work or not. Unless I suppose its CANBUS controlled and something odd is going on with voltage.

Where will I find the noise suppressor on a 2000 W220? Is this is a simple thing to replace?

As always I would appreciate any assistance you might be able to provide!

Thanks Guys
 

television

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The interference is in fact arcing within the wires in the screen where they are partially open circuit, this is why it is no longer so effective at demisting.

One cure is to disconnect the screen at the screen end and put 18 volt through the window for some hour or so, this is the MB fix or try to fix.

The suppressor is only a large electrolytic cap of say 20k MFD or more wired in parallel to the screen. This must be placed as near as possible the the connectors of the screen to have much effect on the suppression of the crackle.

The second cure is to use a house brick
 
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PJayUK

PJayUK

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How does applying 18V fix anything Malcolm?
 

television

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How does applying 18V fix anything Malcolm?

It relies on an arcing principle, make or break one could say, an arc may take place that gives a weld on the wires.

The interference is made worse by the fact that the radio antenna is built into the same screen
 
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PJayUK

PJayUK

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I see, interesting approach!

Not sure how I would do this though!
 

television

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2002 SL500, 216 CL500, all fully loaded
I see, interesting approach!

Not sure how I would do this though!

These are high current things and the power supply to do this must be capable of providing 20 amp
 


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