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Car mirror heater pad

I've done a fair bit of research in the UK and come up with nothing, so cast myself humbly on the mercy of this group. ;-)

I've got an old car which has heated door mirrors. Both the elements are burnt out, and spares are no longer available. The mirrors themselves (the heating was an option) are no problem. So what I'd like to buy are suitable heating mats to replace the originals. RS Components do silicone heating mats for 12 volts, but not in a suitable size which is approx 100 x 50mm. The thickness should be not much more than about 1 mm. The originals appeared rather like a PCB made of thin flexible plastic with silver coloured tracks as the heating element.

I can make copper PCBs at home using conventional methods, and of course a similar method using this plastic material would be great. If I knew what it was and where to get it.

I'd also be willing to pay for a small production run of say 100 if the price was right as other owners are in the same position and winter's coming on...

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    Dave Plowman        dave@davenoise.co.uk           London SW
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Dave Plowman (News)
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Is there room to fit a light bulb or two? You could run two in series for heat without much light.

Another way would be to buy a 240 Volt radiator element and some fibreglass tubing and make up a 12 volt heater that way. Cut the wire off the radiator element - 1/12 of the heater rod would be too little so use double that perhaps.

Reply to
Homer J Simpson

"Dave Plowman (News)" wrote in news: snipped-for-privacy@davenoise.co.uk:

Get some plastic sheet,and some resistive ink(GC silver print?),and make your own. (perhaps laminating the sheet in plastic would increase durability?)

Use riveted terminals to attach the heater to the car's wiring. If you had a flat-bad plotter,you could use that to write the ink onto the plastic,especially for a production run.

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Jim Yanik
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Reply to
Jim Yanik

For a DIY project: take a small plastic sheet that will fit the back of the mirror and get some enameled wire (magnet wire). lay out a coil on the plastic and glue it down to the sheet. That is your heater, and to control the temperature of it - make a constant current source using an LM317T regulator. The data sheet will show how to do it. JTT

Reply to
James Thompson

Reply to
lakewood

If you took a few power resistors and epoxyed them to the back of the mirror that might work. I don't think they would need to disipate much to melt ice in the winter.

Tony

Reply to
Tony Marsillo

Space is a problem. The glass is glued to a thin frame which clips onto the motor assembly. There is some space in the centre of the mirror, but some form of thin heating mat as original would be best.

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    Dave Plowman        dave@davenoise.co.uk           London SW
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Dave Plowman (News)

Then use the 240 Volt radiator element and some fibreglass tubing and make up a 12 volt heater that way.

Unless a wrecker has these your chances look pretty slim. I doubt that cutting down the RS Components pads will work.

Reply to
Homer J Simpson

Hi...

Just a thought, but how's about straightening out as best you can a piece of nichrome from an old toaster and zig zag an appropriate length behind the mirror?

Take care.

Ken

Reply to
Ken Weitzel

Same idea. Just use the fibreglass tubing to prevent shorts.

Reply to
Homer J Simpson

That's another thought. My idea for using NiChrome resistance wire was to weave it through some thin flexible sheet - but don't know what sort of sheet would stand the temperature. First thoughts were mica.

Thing is I believe it's still the way heated mirrors are made so someone must still make the elements. The size isn't critical as the original only covers about 1/2 of the area.

As regards secondhand ones, the stupid wiring has the element on all the time the car is running, and the youngest cars are now 20 years old. When I do find a solution I'll think of a better way. Either switched by the heated rear screen circuit, or incorporate a thermostat.

My feeling is also that their heat output per area is too small for this app.

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    Dave Plowman        dave@davenoise.co.uk           London SW
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Reply to
Dave Plowman (News)

My guess is that cutting one will kill it.

Reply to
Homer J Simpson

Surface mount resistors make good, flat heating elements. (I've seen them used that way in one of those mains-powered slow release air freshener gizmos.)

PS: Whatever method you use, don't forget that the silver coating on the mirror is conductive, & most mirrors only only have a thin coat of paint protecting it, so you'll need to insulate anything powered that presses agains the mirrors.

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Reply to
Lionel

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