206 - defogger barely works

[rzepek2pl]

Hi. Only four out of all the defogger strings (didn't count them all) do their job. All the strings are intact. Anyone knows what might be the problem?

[Hell Razor5543]

You will probably have fine cracks in the others. I had a few on a previous vehicle. It took me and a friend (with a good torch) to find them all (and mark them out with a crayon). One little pot of silver conductive paint and paintbrush later, all lines were working.

[white exec]

Use a testmeter on Ohms to check exactly where the breaks are, and mark them with a permanent marker (just away from the track line).
Mask off either side of the track line with tape, hard up against the track.
Use high quality repair conductive paint - couple of coats. IIRC, Electrolube (the contact cleaner folk) used to make a very good repair paint, containing highly conductive silver. Follow instructions.

If really beyond hope, windscreen insurance might be invoked, but check first that your fitter will actually supply a heated one, and not just a lump of glass.

[spider]

I can only add if you use the conductive paint get a good quality one (the really cheap ones are not brilliant) and when you've finished let it dry for a while.

Take a lot of care removing the masking tape etc too afterwards as its possible to 'lift' the new paint off as it bound to be on the tape too. I think if I do it again I'll have the heated screen on for a few cycles before I remove the tape.

[white exec]

Good point. There isn't a lot of area holding the repair paint on to the narrow tracks.
Might be worth very carefully running a scalpel blade along the paint where it crosses on to the masking tape (after it has dried), so that it is removed along a clean line.
Good advice, too, to let the paint dry and harden thoroughly. I would suggest 24 hours minimum, and another 24 before you apply power. Not a job you want to do twice!

[rzepek2pl]

I made a mistake when diagnosing the strings. After looking at them with a correctly angled flashlight, I spotted cracks on all the strings except the ones that do heat. I just ordered the conductive paint. After I receive it, I'll paint the strings and see if it helps (it should). Thanks guys for telling me where I was wrong.

[white exec]

Just paint the cracks to start with. Don't paint whole track lengths, otherwise you will upset the resistance value of the track.

If only hairline cracks, you can probably get away with using a tiny pointy artist's brush to apply a tiny dob of the paint on the crack. Don't worry if the paint goes on thicker than the track, just not too much wider, otherwise it looks awful. Clean where you're going to paint with a bit of alcohol (or methylated or surgical spirit) on a cotton bud.

[Stickyfinger]

not methylated or surgical spirit, both contain oils that will remain, use Isopropyl alcohol

[white exec]

not methylated or surgical spirit, both contain oils that will remain, use Isopropyl alcohol

Yes, far better. My mistake.

[Paul-R]

Methylated spirits doesn't contain oil to my best knowledge. It mainly consists of 90% ethanol with the other 10% methanol. There is usually a colourant as well with a possibility of minor amounts of other alcohols. But never heard of oil being in it.

For applying the conductive paint you'll probably find that it is too thick for a small brush. A cocktail stick might be a suitable alternative.

[Stickyfinger]

if not oils there is some reactive oil like remains after it dries.

Try spray painting over it......

[Paul-R]

When I was spray painting I would never have dreamt of using meths. I always used the proper degreaser.

[white exec]

Probably not good to use a solvent degreaser on a HRW, though, as the tracks we're talking about here are surface printed on to the screen, and might therefore be weakened by the solvent. IPA (isopropyl alcohol) is the stuff to use here, as recommended above. (Any offset litho printer will have copious quantities of this on site, if stuck.)

Once upon a time, Triplex, Pilkington and others actually embedded the heating wites inside the glass, but no doubt this was expensive. I guess it's still done for heated windscreens.

[Paul-R]

Back in the day when I was in the motor trade one of the gang tried to clean up a printed heated rear window with some cellulose thinners and succeeded in cleaning the tracks right off the glass! Not much value left once he had started.

[white exec]

Don't laugh, but I've actually done that once myself, and on purpose.
Tried, unsuccessfully, to repair the HRW, gave up, and decided to clean it off altogether. No problem - was left with a nice clear rear window.
Only oddity was that, every winter, the Ghost of HRW Marley came back to haunt me, in the form lf a wispy reminder of where the elements once were. Spooky!