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It's the bottom of the first digit on the rhs so 16 would have the bottom of the 1 missing. Just fitted a new zebra strip from rpi engineering and followed their youtube video. Cleaned the contacts until they were spotless using contact cleaner and wooden cocktail sticks. Put it back together and the above problem, so took it apart again and found nothing wrong reassembled and the same fault.
I did the strip because in the colder weather it lost bits here and there but worked fine once warmed up or the milder drier weather arrived. I'd like to say that all the pixels were there on a warm day but I'm doubting myself now.!
Is it possible one of the copper contacts isn't quite as spotless as I thought? Or maybe I should clean the new zebra strip with contact cleaner incase that's got something on it? It came stuck to a piece of card with sellotape which came off in one piece. Run out of time today but thoughts welcome before I strip it down again hopefully tomorrow.

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Marty's pdf of how to do it is very good, even my mate Danny who is as ham fisted as they come was able to follow and get a full set of pixels. Marty's instructions are here http://p38webshop.co.uk/RRdocs/P38%20HEVAC%20Pixel%20Fix%20v2.pdf and may be more comprehensive than anything from RPi.

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Site not available sadly.

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I didn't find the job at all difficult to be fair but I am curious as to how a solid lump as such, the new zebra strip block that is , can carry current to each individual contact without shorting across! Leccy stuff isn't my strong point hahaha!

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Try from here http://p38webshop.co.uk/index.php?route=product/category&path=71 (the last one), when you click on it, it should immediately download the pdf and open it in Acrobat. This assumes from a laptop or desktop, no idea what it will do on a phone though.

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That worked on my phone ta.
Identical really to the rpi video so I've done it right. I'll try disassembling it again tomorrow and clean the zebra strip this time.
Dunno how these things work but is it possible the screen itself is faulty?

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The Zebra strip is basically a sandwich of very thin materials - they're layered with a conductive strip/insulating strip/conductive strip etc all the way along them - so the current flows though, but is isolated every other layer, so that between the copper contacts on the PCB and the contacts on the screen, they always have conductive strips, and isolating ones, so one set won't short to the next one etc.

Re not getting all the pixels.... cleaning the zebra strip could help, as if there's some dirt or old adhesive on it from where they stuck it down, then it could be insulating where it should be conducting. The other thing to check is the screw holes/mounts that hold the PCB to the plastic fascia. There's only 2 of them on the bottom of the screen, and I've seen a number of times where they have cracked, so that when you tighten the screw up, it doesn't give enough grip and thus not enough pressure between the screen and the PCB, and you can still miss pixels. If that is the issue, I've sometimes repaired them by re-melting the plastic with a soldering iron where it's cracked - but you have to be careful to not do any more damage.

I've got a handful of HEVAC screens which have a fault in them where one or 2 pixels still don't work, and they are actually a fault in the screen somewhere - but if you got all the pixels before, then I'd say the chances aren't high of the screen having failed now - unless something got scratched/damaged when you removed the old residue from the original ribbon strip.

If you can post up a picture of the back of the HEVAC face plate, then I might be able to tell if the screw mounts are an issue or not.

Marty

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Cheers marty, it's all back together now but there was no screw plastic damage and I cleaned the zebra strip just incase.
I even tightened the 3 screws around the screen first before doing the others but kept getting the same result after 3 trys at it, got fed up as lots of other jobs were calling so stuck the plastic all back together so I could still use the car.
I can't say, annoyingly, if ALL the pixels WERE there in warm dry weather, I just know the screen was much better in warm weather. I've not helped myself there by not actually noting if there were pixels missing, I just remember loads were in cold weather.

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Also, I only used a wooden lollipop stick, cotton buds and contact cleaner on the copper contacts, cotton buds and contact cleaner only on the screen which came away clean anyway after removing the old ribbon.
It's all pointing to a dodgy screen methinks.

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OK. Today I've managed to get another hvac for not much money but it's working condition are unknown AND it's off a poverty spec model but the same year, 2001, as my dhse. So it has no heated screen, seats buttons. My question if anyone knows is are all the screens the same so I could pinch the display screen out of this one and fit it in mine?

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Yes, The screens are all the same... it's just the actual plastic face panel, buttons, and firmware that are different between the HEVAC models - but the LCD screen is identical

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Cheers Marty!

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Thought I had updated this, sorry.
Used, unknown condition, screen fitted into my hvac body and all is well.