HELP!! Rear Windscreen de-mister

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babz

Active Member
Joined
Jan 21, 2011
Messages
130
Location
Newcastle Upon Tyne
Car
1996 Mercedes C180
hi, ive just bought a 1996 mercedes c180, and there are a few problems. one of which being my rear de-mister wont work! i think the fuse has gone but im not at all familiar with mercs :dk: can anyone tell me where to find the fuse? and better yet which fuse it is? any help will be much appreciated.
 
Hi,
The fuse box is on the drivers side under the bonnet, just in front of the windscreen. The fuse application list should be in the lid of it.
Does the indicator light on the heated rear screen illuminate when you swith it on?
 
yes ive located the fusebox and fuse. there doesnt seem to be a problem there with the fuse itself. and yes the little red light on the demister button does come on when i press it.
 
Check the connections and elements on the rear windscreen. Chances are that an element wire has broken and you now have an open circuit=no heated windscreen!
 
See if you can trace where the wires start/finish on the windscreen - the connections may well be in the boot or under the parcel shelf. When you've found them, switch the heater on and check for voltage.

I would imagine that one of the 'vital' element wires has broken - ie not just one of the cross-screen wires that do tend to go but one of the main ones that either supplies the 12V or the earth.
 
ill have a quick rummage and see what i can uncover. i hope its not too big a job, im a complete novice so ill probably end up coming back on here for more help
 
Where do you live, i am sure there is some one on here who wuld be happy to have a look.
 
i live in newcastle

ive had a look at the rear screen and cant seem to trace where the connectors could be? any ideas?
 
Did you actually replace the fuse with a new one?

I ask because it's not unknown for a fuse to fracture at the thinnest point, and a quick glance can make you think it's OK when it isn't.
 
the fuse is intact, no breaks or cracks at all, ive even given it a good scrub with fine sand paper. i cannot find a 40amp fuse to replace it with. apparently theres no such thing
 
the fuse is intact, no breaks or cracks at all, ive even given it a good scrub with fine sand paper. i cannot find a 40amp fuse to replace it with. apparently theres no such thing

Look in the toolkit, there is often a pack of fuses in there (and a fuse removal plastic tool)

R
 
the tool kit?! i didnt get one with the car! i wasnt aware that there was such a thing DAMN!
 
The rear window demister shares a relay, the N10, with the intermittent wipers and indicators/hazards, worth checking that out, see… http://www.mbclub.co.uk/forums/favourites/93685-how-repair-resolder-relay.html

To test that 40a fuse, remove the radio fuse and put your 40a fuse into the radio fuse holder…if the radio works then the 40a fuse is good. Put the original radio fuse back where it belongs.

Dec
 
yes ive located the fusebox and fuse. there doesnt seem to be a problem there with the fuse itself. and yes the little red light on the demister button does come on when i press it.
got the same problem on my c180
 
Chances are it's a fault in the screen itself in that case. Best get it checked out by a dealer or specialist.
 
Easy to check a surface printed rear screen demister with a test light.
Assuming there is power/return to the rear demister.....

Connect one end of the testlight to a known good earth.
Now run the testlight down the middle of the window, with a firm push as you go past each element. (Not firm enough to break the element!)

Testlight illuminates dimly = good element
Testlight illuminates brightly = break in element on the earth side of the testlight
Testlight does not illuminate = break in element on the feed sid of the testlight.
 
The rear window demister shares a relay, the N10, with the intermittent wipers and indicators/hazards, worth checking that out, see… http://www.mbclub.co.uk/forums/favourites/93685-how-repair-resolder-relay.html

To test that 40a fuse, remove the radio fuse and put your 40a fuse into the radio fuse holder…if the radio works then the 40a fuse is good. Put the original radio fuse back where it belongs.

Dec
on my car the relay clicks when i push the button and it is light in the button but nothing happens..
want to fix it asap because we have snow and frost up here in north
 

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