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Heated rear screen question. Triumph GT6
John Bonnett - 13/2/13 at 08:19 PM

The rear screen has a factory fitted element and it works but not very well. I checked with a Multimeter and it appears to be only drawing an Amp or so; a tenth of what it should be drawing. Mist clears in patches and most of the strands clear the screen in places which seems to indicate they are all continuous. But obviously not sufficient to pass the necessary current.

Replacement heated rear screens are unobtainable and I just wondered if anyone could come up with a fix for me.

Thank you for your help.

John

austin man - 13/2/13 at 08:37 PM

can you wire in one of the electric fan heaters ? years ago you could buy stick on elements not so sure about now though

austin man - 13/2/13 at 09:46 PM

like this

Lucas Rear Screen Heater Demister New Old Stock | eBay

John Bonnett - 13/2/13 at 09:47 PM

quote:
Originally posted by austin man
can you wire in one of the electric fan heaters ? years ago you could buy stick on elements not so sure about now though





Thank you for the suggestion but if possible I'd like to get this one working if possible.

austin man - 13/2/13 at 09:50 PM

or this

REAR WINDOW HEATER RETRO / KIT CAR / CLASSIC CAR / MINI | eBay

austin man - 13/2/13 at 09:54 PM

you can also buy a repair substance

REAR WINDOW DEMISTER HEATER REPAIR Conductive paint | eBay

spiderman - 14/2/13 at 12:10 AM

A GT6 with a working heated rear window? I thought that was just an urban myth John.

John Bonnett - 14/2/13 at 07:45 AM

quote:
Originally posted by austin man
you can also buy a repair substance

REAR WINDOW DEMISTER HEATER REPAIR Conductive paint | eBay







Yes, now this is the kind of thing I was thinking about but has anyone any experience of using it? I imagine I'd have to use masking tape placed very carefully at the side of each filament and then paint over the top. It's certainly not that expensive and providing I could apply it without making a dog's breakfast of the job it will be worth a punt.

So thank you Mt Austin Man for your help.


You are probably right Spider but worth a try

britishtrident - 14/2/13 at 09:00 AM

Have you actually had the car on the road ? -- Most owners report in normal no-artic weather on the GT6 the rear screen clears pretty quickly without the heated rear screen due to the position of the rear extractor vent.

John Bonnett - 14/2/13 at 12:57 PM

quote:
Originally posted by britishtrident
Have you actually had the car on the road ? -- Most owners report in normal no-artic weather on the GT6 the rear screen clears pretty quickly without the heated rear screen due to the position of the rear extractor vent.






Thank you BT. I've done 7000 miles in the car since last April and have driven it in all conditions. And yes, you are right, the rear screen does clear providing it's not too badly misted up. But yesterday even with the rear and front quarterlights open it would not clear even with the screen heater doing its best.

The heated screen is clearly not working properly and my feeling is that the filaments have for whatever reason lost a lot of their conductivity which will account for it only drawing a tenth of the 10 Amps that it is rated at. All the filaments are continuous but the strange thing is that they clear in patches along the same filament and this is what I cannot understand.

Mr Austin Man kindly found the conducting paint and if I am right about the problem this might well be the answer.

Any suggestions will be greatly appreciated.

Thank you

John

Slimy38 - 14/2/13 at 01:13 PM

quote:
Originally posted by John Bonnett
quote:
Originally posted by austin man
you can also buy a repair substance

REAR WINDOW DEMISTER HEATER REPAIR Conductive paint | eBay







Yes, now this is the kind of thing I was thinking about but has anyone any experience of using it? I imagine I'd have to use masking tape placed very carefully at the side of each filament and then paint over the top. It's certainly not that expensive and providing I could apply it without making a dog's breakfast of the job it will be worth a punt.

So thank you Mt Austin Man for your help.


You are probably right Spider but worth a try


In my experience, this conductive paint only connects the two ends of a broken strip, it can't act as a heating element itself. When you see one of these repairs in action, the strip does it's job but you have a small bit of ice just where the repair is.

If you already have it defrosting in patches but all along the strips, I don't believe this is going to improve things.

John Bonnett - 14/2/13 at 03:51 PM

quote:
Originally posted by Slimy38
quote:
Originally posted by John Bonnett
quote:
Originally posted by austin man
you can also buy a repair substance

REAR WINDOW DEMISTER HEATER REPAIR Conductive paint | eBay







Yes, now this is the kind of thing I was thinking about but has anyone any experience of using it? I imagine I'd have to use masking tape placed very carefully at the side of each filament and then paint over the top. It's certainly not that expensive and providing I could apply it without making a dog's breakfast of the job it will be worth a punt.

So thank you Mt Austin Man for your help.


You are probably right Spider but worth a try


In my experience, this conductive paint only connects the two ends of a broken strip, it can't act as a heating element itself. When you see one of these repairs in action, the strip does it's job but you have a small bit of ice just where the repair is.

If you already have it defrosting in patches but all along the strips, I don't believe this is going to improve things.




So, if that's the case then in your opinion painting over the filaments won't actually allow more current to flow?

Slimy38 - 14/2/13 at 05:27 PM

quote:
Originally posted by John Bonnett

So, if that's the case then in your opinion painting over the filaments won't actually allow more current to flow?


Going back to basic current equals voltage divided by resistance, then yes, reducing the resistance will increase the current. But you'd need to find the fine line between it heating up the screen and just popping the fuse.

I'm sure there's something I'm missing regarding potential difference on zero resistance loads but I can't remember that bit of my electronics A level!