Car rear window demister not working

ClubMan

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43,870
My 142 Dacia Sandero rear window demister is not demisting even though (a) all fuses are fine (b) power (14-15V) is getting to the demister "tracks" and (c) there is no break in continuity in the "tracks". So everything looks fine but it simply doesn't demist the window (or very barely does - maybe a couple of mm either side of the window "tracks"). Any ideas?
 

RichInSpirit

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822
Not a mechanic but maybe a bad electrical connection somewhere on the circuit that is not letting the required amps through.
Possibly corrosion where the earth wire coming from the demister is bolted to the chassis. Or a corroded contact in the switch for the demiser. It might be possible to find the bad connection and give it a clean with a wire brush. And spray a bit of Wd40 on it after.
 

ClubMan

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43,870
Thanks. I would be surprised if there was corrosion as the car is not that old and in very good nick with no sign of any moisture ingress anywhere that I can see. But I will try to investigate the circuit and see if I can find anything wrong. On the other hand I did commit the cardinal sin of leaving a wet umbrella in the boot not too long ago and that may have coincided with the problem and maybe THAT caused some corrosion... Thanks again for the suggestions.
 

SparkRite

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1,218
Are ALL tracks producing some sign of heating, ie. some demisting occurring around EVERY track?

If not, I strongly suspect that you have a break in the grid somewhere.
If they are, lets hope it is a simple as a 'gammy' earth.
 

mathepac

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I remember years ago repairing the rear window heater of a Ford Cortina with stuff from a "nail-varnish" type bottle. I'm uncertain at this remove if I was sticking the "tracks" to the glass or repairing breaks in said track. Try motor factors but I doubt you can get the stuff any more.
 

SparkRite

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1,218
I remember years ago repairing the rear window heater of a Ford Cortina with stuff from a "nail-varnish" type bottle. I'm uncertain at this remove if I was sticking the "tracks" to the glass or repairing breaks in said track. Try motor factors but I doubt you can get the stuff any more.
I think you can still get it, a conductive liquid that dried forming a 'bridge' over any break/crack in the track.
Mixed results, anecdotally, I heard of a guy who 'popped' his rear screen by the repair generating a hot spot and therefore thermally cracking the glass.
 

Leo

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10,384
Unfortunately Leo's stuff is not much use to you @mathepac as it's water soluble.
I didn't notice that! Thanks.

I bought non-solvable stuff years ago from a UK electronics supplier that has gone out of business since, I linked RS as it was the only link that popped up in a search. I usually avoid them as they're expensive compared to most of the competition.
 
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