rear windscreen de-mister faulty

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dalthepostie

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Joined
Nov 17, 2014
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2
Car
mb 320cls
I recently purchased a used cls320 and am having an intermittent fault with the rear windscreen de-mister. Sometimes it works and sometimes it doesn't. Has anyone else had this problem and is anyone aware of a fix?

Cheers
 
W211 Heated rear window

Heated rear window in my W211 E270 CDI rear windscreen de-mister
Hi, I have the same problem. Ide like to locate the connector from the rear of the SAM control module (N10/2) to the heated rear window. Can anyone give me the plug connector number on the back of the Rear Sam please?
Thanks in advance.
 
Although not a Mercedes, I bought a new to me run around car and the heated rear window only worked on the top half. I took it back to the garage where I had bought it and they knocked the rear screen out and replaced it with new.

I asked why they had taken this drastic action and they said that it was cheaper to do it this way than to spend time fault finding!
 
My 2008 CLK has just 2 HRW lines working. Close examination shows the two verticals do not go from top to bottom, both have gaps at row 10. The gaps are symmetrical. Are they supposed to be like that please?
 
Any normal gaps are usually at the top, example of gaps on a W202 below.

Can you put up a picture?


Dec

Rear window heater W202.jpg
 
Thanks. Done so. Photo on both vertical lines at same horizontal. Note, this is not the C220. It's a 2008 CLK 500.
 

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My previous picture, of a w202, is just an example, to illustrate all the gaps in wiring; yours may not be the same set-up.

Your two pictures do look normal, because the look to have exactly the same gaps.

Others, with the same car, might be able to contribute more info on this.


Below, in picture, is something you can try, to see if any wiring is damaged at the edges & top, it’s off a W202, yours might be the similar.


Dec

night and day.jpg
 
Thanks, I shall do that tomorrow. If it is a relay problem, would it mean no heating at all or can there be a partial fault please? If I can determine which relay it is I can test continuity.
 
In the boot, see this PDF… http://www.benzworld.org/forums/attachments/c209-a209-clk-class/435204d1333103820-all-fuse-relay-box-details-w209-w209-n10-2-relay-assignment.pdf


Source… http://www.benzworld.org/forums/c209-a209-clk-class/1629567-all-fuse-relay-box-details-w209.html


Also, this wasn’t solved but worth a read, see… http://www.benzworld.org/forums/c209-a209-clk-class/1925257-demister-not-working.html


Try replacing the existing rear window fuse, anything else share that fuse?


It’s best to look at screen at night if using a smart phone light.


Dec
 
Thanks again for all that info. Photos did not show hidden lines. Will try after dark. Didn't have a convenient 12v source to test relay so might buy second hand one. I do though have 2 lines working so would that rule out the relay being u/s please?
 
The relay could be working but could have a very bad/burned contact, best to try a replacement; there is probably another similar relay elsewhere in the car that you could try, instead of buying a new one. Its very odd that 2 lines are working and the rest are not.


bad relay contacts - Google Search


Any other electronics not working in the car?


Dec
 
There is a similar relay next to it. Not sure what it does. Different number so wary of trying it. Everything else on car working.
 
Best not to mess up something else then.

You could open the relay and have a look.

Dec

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Had a look. Seems in excellent condition. No visible coil damage. Used very fine emery paper on contacts. Weather not suitable for testing unfortunately.
 
Look for any breaks in the lines of copper. You can buy electrical paint to bridge any gaps.
 
If the elements are printed on the surface of the screen, this is how to test.
With screen turned on, using a testlight with one end connected to earth, firmly (not TOO firmly!) draw the testlight down the middle of the screen across each element in turn.
Testlamp lights dim - element is working
Testlamp lights bright - break between where you are testing and earth
Teslight stays off - break between where you are testing and supply.
You can then use the above to track (pun intended) down exactly where any breaks are.
 
In this mornings damp weather, noticed a few lower lines are now working. Maybe an earth problem. Will look at accessing the wiring behind the pillars.
 
Thanks again Dec. Tabs on CLK are not so easily accessible. Frost Fighter is USA company. Not seen any gold/brown coloured on sale in UK and don't want silver repairs so will look at electrics first.
 

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