Repairing all the tracks on rear demister - bin it or paint?

[sgtBerbatov]

I have a Peugeot 107, and it's currently my daily driver as my Corolla is still up on blocks waiting for me to sort it out. The weather - as you might have seen - has gone a bit cold so I need to demist the rear window every morning.

Now last year I remember 2 tracks were broken on the rear window which didn't cause an issue. However, this year the rear window doesn't demist at all. On closer inspection all of the tracks are broken.

Why? Well we got married this year and the mother in law thought it'd be all cute etc to tie a banner around the car and stick a "Just Married" sign in the back window. I cleared the plastic that was wrapped around the car, which had transferred its paint to the car which I can't get off, while the wife took off the Just Married sign. The sellotape they used ripped the heating elements off the window.

Now I know I can buy liquid metal to connect the lines, but I've read that the resistance of the paint is quite high. Can I get away with painting all the tracks together or do I risk causing the window to smash when the element is turned on? Or should I just take it off and replace it with a second hand boot lid?

[TooMany2cvs]

When I've tried the "element repair" paint in the past, it's simply not worked - my presumption is that there's a non-conductive layer over the conductive element itself, so it doesn't make contact. It'd make sense if there was, otherwise there's a risk of short if you've got something metallic in there.

[kev b]

I have used conductive paint many times with success however the area must be completely clean and the gap not too large.

I dont think you will have much success if inches of track are missing.

Also I would think you could obtain a complete tailgate in the right colour for not much more than the cost of conductive paint.

[sgtBerbatov]

TooMany2cvs said:

When I've tried the "element repair" paint in the past, it's simply not worked - my presumption is that there's a non-conductive layer over the conductive element itself, so it doesn't make contact. It'd make sense if there was, otherwise there's a risk of short if you've got something metallic in there.

I've seen it done and it's looked fairly simple to achieve. But I don't know of anyone doing lots of tracks in one area. But it makes sense, if it doesn't stick it's useless.

kev b said:

I have used conductive paint many times with success however the area must be completely clean and the gap not too large.

I dont think you will have much success if inches of track are missing.

Also I would think you could obtain a complete tailgate in the right colour for not much more than the cost of conductive paint.

There isn't inches of track missing in one line, it's like 1cm/2cm stretches of track across multiple tracks in near enough the same area.

I've looked on eBay and so far they're coming out at around £45 but all are collection only 100 miles away up north or down south.

[lucido grigio]

I'd replace the tailgate if the whole lot have gone but be careful to get one without another duff window.

I'd want to check all the lines with a meter for resistance when buying but if you buy one online that's obviously not an option.

I remember when breakers were walk into the yard and remove stuff yourself.

[TooMany2cvs]

kev b said:

Also I would think you could obtain a complete tailgate in the right colour for not much more than the cost of conductive paint.

Don't even need worry about paint colour for a 107 - the tailgate is just the glass - and C1 is the same, bar the badges. Aygo is a different shape, due to the different rear lights.

[kev b]

You might find a tailgate on local media, facebook, gumtree etc or even a local scrapyard if one still exists in your area.

I would definitely have a go with the paint, make sure you degrease with thinners/isopropol alcohol first, should work ok especially if the line is thicker than normal.

If the track is tarnished a polish up with compound/t-cut/solvol will help ensure continuity.

[GreenV8S]

I've seen a few adverts for aftermarket demist grids which you cut to size and stick to the glass. They seem to average about £50 plus so a new window might work out cheaper.

I've never used the conductive repair paint but these kits seem quite common and I expect the basic principle is sound. Is any of the existing element still left? If not, you would need to effectively 'paint' a whole new element, which I can't imagine working. But if you just need to bridge a gap of an inch or two in every element, that might be realistic.

As an alternative, it's possible to get small electrical fans with an integral heater designed for kit car windscreen demisters and you might think about pointing one of those at the glass. They won't put out much heat, but I don't suppose those demist elements put out much heat either.

[Glassman]

My experience of the conductive 'repair' paint is that the product always appears to be too viscous to work with. In any case, as soon as you crack open the bottle it starts to cure.

It's not the right colour (silver paint) so will always show against the orange/oxide. If the break is any more than a millimeter or two: forget it. Fine-line masking and a clean surface are essential.

Second hand (or new) will be a better shout IMHO.

Edited by Glassman on Wednesday 13th December 12:54

[sgtBerbatov]

I think I'm going to source a replacement boot lid. I've read that the paint can cause heat spots as it's often a higher resistance than the original tracks. So if I have a row of them to do it'll probably shatter the glass.

I'll have to do some hunting around scrap yards for it I think instead of online. At least I can test continuity in person rather than gambling with it online.

Thanks everyone.

[TooMany2cvs]

sgtBerbatov said:

I'll have to do some hunting around scrap yards for it I think instead of online.

Can't imagine a C1/107 tailgate is going to be exactly unobtainium... It's not even as if you need to worry about the colour.

Here y'go...
£65 delivered
http://www.ebay.co.uk/itm/152769873499
£73 delivered
http://www.ebay.co.uk/itm/192383520898
£75 delivered
http://www.ebay.co.uk/itm/152610140191
...and loads of others.

[sgtBerbatov]

TooMany2cvs said:

sgtBerbatov said:

I'll have to do some hunting around scrap yards for it I think instead of online.

Can't imagine a C1/107 tailgate is going to be exactly unobtainium... It's not even as if you need to worry about the colour.

Here y'go...
£65 delivered
http://www.ebay.co.uk/itm/152769873499
£73 delivered
http://www.ebay.co.uk/itm/192383520898
£75 delivered
http://www.ebay.co.uk/itm/152610140191
...and loads of others.

But I've no way of knowing whether the tracks work or not. That's the problem with getting them online. Especially if they've been stored in a dodgy way. Thanks for the links though I'll see if any of them are near me.

[TooMany2cvs]

sgtBerbatov said:

But I've no way of knowing whether the tracks work or not. That's the problem with getting them online. Especially if they've been stored in a dodgy way.

You aren't going to be able to test one in a scrappy, either.

sgtBerbatov said:

Thanks for the links though I'll see if any of them are near me.

Those prices include delivery to your door...

[Dogwatch]

The conductive paint was ok for the after-market self-adhesive heaters (anyone remember them?) but always showed up as a patch as it was nigh-on impossible to apply it at a comfortable angle.

I think the OE ones are in a different league with much finer elements.

I've still got a bottle of Comma Electrocure electrical conductor paint which passed its throw out date a decade or more ago.

[sgtBerbatov]

TooMany2cvs said:

sgtBerbatov said:

But I've no way of knowing whether the tracks work or not. That's the problem with getting them online. Especially if they've been stored in a dodgy way.

You aren't going to be able to test one in a scrappy, either.

sgtBerbatov said:

Thanks for the links though I'll see if any of them are near me.

Those prices include delivery to your door...

I can throw a multimeter at it to test continuity though when I'm at the scrap yard. I can't do it online.

The top one you sent though isn't too far from me, so I'm going to go pay them a visit at the weekend.

[TooMany2cvs]

sgtBerbatov said:

I can throw a multimeter at it to test continuity though when I'm at the scrap yard.

All that'll tell you is that at least one element works.

[xstian]

Why don't you claim off your insurance and get a new window. You'll have to pay an excess (£50?), but at least you know it will work.

[Glassman]

xstian said:

Why don't you claim off your insurance and get a new window. You'll have to pay an excess (£50?), but at least you know it will work.

A couple of broken lines on the demister would be covered?

[PositronicRay]

Glassman said:

xstian said:

Why don't you claim off your insurance and get a new window. You'll have to pay an excess (£50?), but at least you know it will work.

A couple of broken lines on the demister would be covered?

Now wouldn't that be nice, sort my de-lamination at the same time.

[JoeBolt]

sgtBerbatov said:

I think I'm going to source a replacement boot lid. I've read that the paint can cause heat spots as it's often a higher resistance than the original tracks. So if I have a row of them to do it'll probably shatter the glass.

I'll have to do some hunting around scrap yards for it I think instead of online. At least I can test continuity in person rather than gambling with it online.

Thanks everyone.

Ohm's Law: V = IR or: I = V/R

If the paint increases the resistance of the heating element, it will reduce the current flow.
Think of current as heat. If the paint doubles the resistance of the circuit, the current will be half.
If the resistance is too high, there simply won't be enough current flowing to produce any heat. The heater won't work.

That's how it is now. The current won't flow through the glass because glass has very high resistance, i.e. it is a good electrical insulator.