Heated rear window de-mister

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D366Y
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Heated rear window de-mister

Postby D366Y » Thu Nov 22, 2018 7:35 pm

Evening all!

Today was the first time for this winter I've needed to scrape all that pesky ice off the car before heading to work.
My heated rear window has never worked on the laser, but I'm keen to finally change that - just wanted to see what the best pointers were with where to start?

The light comes on when I press the button but nothing else happens. It used to be that one very small patch (in the middle on one line) cleared up a little but now that has gone.

I would guess I need to multi-meter somewhere to ensure there is a current getting to the window, and then re-paint the lines using electrically conductive paint but wanted to see what you guys recommended first...

Thanks!
Danny

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Re: Heated rear window de-mister

Postby Jasonmarie » Thu Nov 22, 2018 8:24 pm

I am sure you can buy some paint to make the heater to work again but the earth on my old Capri needed cleaning once when mine stopped and was fine after that as it’s sits on the boot struts .
Ford Capri 2.0 Laser 1987 Mercury Grey ....... :beer:

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Re: Heated rear window de-mister

Postby pbar » Fri Nov 23, 2018 7:03 am


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Re: Heated rear window de-mister

Postby D366Y » Fri Nov 23, 2018 9:35 am



Thanks Paul, I was trying to look for your conductive paint thread as I remember reading it at the time - annoying that Maplins have now closed though!

Where is the best place to test the current on the window? I would guess on the thick strip each side of the window....?

Cheers

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Re: Heated rear window de-mister

Postby pbar » Fri Nov 23, 2018 10:27 am

I think in my case, I unplugged the connector from the rear screen demister and put the multimeter probe to that, but I would only get a reading with the switch on from a randomly chosen new earth point, which told me that the 'proper' earth was faulty. I never knew why or where it had failed, I just created a new earth and connected to a point behind some removable trim in the boot.

This got the demister working again, and it was then a case of trying different points along the 'lines' to see why some were failing. I could then pinpoint where the lines were broken/failing, and the conductive paint worked a treat in these areas and it has been 100% ever since, and it's a daily car too.

Diagnosing the issues took all the time. I could find the small bottle of the paint I used and see if it has a manufacturer/make on it if you like, but I would have thought most electronic or Maplin type shops will have it.

I did notice bespoke kits for doing this were very expensive, compared to a general electronic conductive paint which worked a treat. A permanent fix.

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Re: Heated rear window de-mister

Postby D366Y » Fri Nov 23, 2018 11:32 am

pbar wrote:I think in my case, I unplugged the connector from the rear screen demister and put the multimeter probe to that, but I would only get a reading with the switch on from a randomly chosen new earth point, which told me that the 'proper' earth was faulty. I never knew why or where it had failed, I just created a new earth and connected to a point behind some removable trim in the boot.

This got the demister working again, and it was then a case of trying different points along the 'lines' to see why some were failing. I could then pinpoint where the lines were broken/failing, and the conductive paint worked a treat in these areas and it has been 100% ever since, and it's a daily car too.

Diagnosing the issues took all the time. I could find the small bottle of the paint I used and see if it has a manufacturer/make on it if you like, but I would have thought most electronic or Maplin type shops will have it.

I did notice bespoke kits for doing this were very expensive, compared to a general electronic conductive paint which worked a treat. A permanent fix.


You are a star Paul!

Thanks for this, I'll find some paint no problems, and I'll have a play around with the multimeter over the weekend.

Am I right to think that there is a positive entry on the drivers side and the earth point should be the drivers side? I remember seeing some covered spade clips around there before so will have a poke around - thanks for the help!

Quick Edit, took two minutes to find this paint :lol:

https://www.bareconductive.com/shop/ele ... aint-50ml/ - I've seen it advertised before as being skin friendly as well and was used in a music video once finished. I think some students invented it as part of their course but looks like a good price :)

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Re: Heated rear window de-mister

Postby Paul G » Fri Nov 23, 2018 4:19 pm

I've used this stuff over the years and it seems to work but does leave little silver "blobs" visible from the outside of the glass.

https://www.halfords.com/motoring/paint ... ter-repair

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Re: Heated rear window de-mister

Postby D366Y » Sun Nov 25, 2018 7:25 pm

Have done some investigating today with the old multi meter.... there is a constant current of around 11.4V from the positive on the drivers side and the negative on the passenger side... however when I try and test the current on each individual element there is no current being registered at all... I've ordered some paint so am thinking I will just paint more or less everything as much as I can and hope for the best??

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Re: Heated rear window de-mister

Postby pbar » Tue Nov 27, 2018 7:16 am

D366Y wrote:Have done some investigating today with the old multi meter.... there is a constant current of around 11.4V from the positive on the drivers side and the negative on the passenger side... however when I try and test the current on each individual element there is no current being registered at all... I've ordered some paint so am thinking I will just paint more or less everything as much as I can and hope for the best??


I think it would take several decades to paint them all Danny :) You can't really slosh it on, you have to be very precise with it. I put a piece of tape either side of the line where my break was, then delicately painted on the paint, a couple of coats, and that was it, been ok ever since and you can't tell.

So you get a reading with the switch on, measuring before any of the lines on the screen. Perhaps you have a break right at the beginning then, have you tried measuring there?

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Re: Heated rear window de-mister

Postby D366Y » Tue Nov 27, 2018 8:57 am

pbar wrote:
D366Y wrote:Have done some investigating today with the old multi meter.... there is a constant current of around 11.4V from the positive on the drivers side and the negative on the passenger side... however when I try and test the current on each individual element there is no current being registered at all... I've ordered some paint so am thinking I will just paint more or less everything as much as I can and hope for the best??


I think it would take several decades to paint them all Danny :) You can't really slosh it on, you have to be very precise with it. I put a piece of tape either side of the line where my break was, then delicately painted on the paint, a couple of coats, and that was it, been ok ever since and you can't tell.

So you get a reading with the switch on, measuring before any of the lines on the screen. Perhaps you have a break right at the beginning then, have you tried measuring there?


I tried to measure as close as I could to the beginning of each line/element and still reading 0.02 or something minimal and pointless like that so I thought of making it a longer term project and doing a few lines each weekend rather than trying to do it all at once.

I had planned to mask up either side of the line and see how I got on with it

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Re: Heated rear window de-mister

Postby pbar » Tue Nov 27, 2018 10:16 am

OK Danny, sounds like a plan :)

Good luck with it, be sure to post how you get on, would be very interested to know.

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Re: Heated rear window de-mister

Postby D366Y » Tue Nov 27, 2018 10:56 am

pbar wrote:OK Danny, sounds like a plan :)

Good luck with it, be sure to post how you get on, would be very interested to know.


I will do don't worry! I'm going to have to find something to cover it with as am worried that the paint will fade over time/be washed away by any water that might occur from condensation.... will let you know what happens!