SiWhite Posted December 20, 2009 Share Posted December 20, 2009 I've just got round to wiring in my heated windscreen after it was fitted by Autoglass about 18 months ago. I get great heating down a central two inch stripe, and a bit at each end. The screen only draws about 10 amps - a lot less than I was expecting. I've wired it so that there is a positive feed at each side, and a central ground. It's wired through a standard realy and switch - no timer etc. It's clearly not working as it should - is it a faulty unit, or is my wiring likely to be wrong? Quote Link to comment Share on other sites More sharing options...
western Posted December 20, 2009 Share Posted December 20, 2009 Try a 70amp relay. & see the other heated screen thread. here Quote Link to comment Share on other sites More sharing options...
mmgemini Posted December 20, 2009 Share Posted December 20, 2009 I wired mie up on Thursday. It seems to work fine. I used two timer relays fron here http://www.vehicle-wiring-products.eu/VWP-onlinestore/relays/timers.php The wire I used was ref25 the thinwall cable . http://www.vehicle-wiring-products.eu/VWP-onlinestore/cable/thinwall.php there's a run of nearly eight metres from the relay to the 'screen Quote Link to comment Share on other sites More sharing options...
Litch Posted December 20, 2009 Share Posted December 20, 2009 Even if the screen has been installed correctly the elements can break over a period of time resulting in a striped appearance, if the screen was twisted when being installed then it is quite possible that some of the elements were broken then. My original heated screen did not really suffer with this problem although a few areas that did not clear immediately did appear after a few years of use. When a stone made replacement necessary (£40 on windscreen insurance) the replacement screen suffered with this from day one and over the past 3-years has got to a state where now where 50% of the screen does not clear immediately. This area is not grouped together but spread out across the whole width resulting in stripes. I can live with it for another year but I think that a new screen will be in order by next winter. Quote Link to comment Share on other sites More sharing options...
SiWhite Posted December 20, 2009 Author Share Posted December 20, 2009 Thanks for the thoughts - I would automatically assume that the elements had broken down, but the screen is only 2 years old and I'd say about 85% are not working - surely they would last longer than this, especially with no power passing through them? Truck only drives a few thousand miles a year. I'm planning a bit more fiddling with my wiring tomorrow but am generally assuming it was handled roughly during installation and ruined by Autoglass. Seems strange it's drawing so few amps.... Quote Link to comment Share on other sites More sharing options...
errol209 Posted December 21, 2009 Share Posted December 21, 2009 Seems strange it's drawing so few amps.... Hmmm. Low amps = low power (at 12V), which is why it isn't working very well, and low amps could also mean a high resistance (at 12V). The elements in the screen run horizontally, I think, so your description suggests all the elements are working? Did you use nice big manly wires? I'd be looking at 56/0.3 (40A) for each feed and two runs of that for the earth connection. Did you connect the other end of the earth to anything other than the engine, gearbox or battery negative? At these kind of currents even a slightly poor earth could give you the symptoms you have. Quote Link to comment Share on other sites More sharing options...
SiWhite Posted December 21, 2009 Author Share Posted December 21, 2009 Thanks for the suggestions folks. Errol, the elements run vertically. I tried a fused supply directly from the battery terminals this morning and the same symptoms presented themselves. It's clearly drawing power and clearing the sections of the screen which are undamaged. New screen going in on Wednesday - by which time the cold snap will have passed! Quote Link to comment Share on other sites More sharing options...
errol209 Posted December 21, 2009 Share Posted December 21, 2009 Errol, the elements run vertically. Damn, nice theory though. Quote Link to comment Share on other sites More sharing options...
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