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Testing demist / heated screen
wonderfulweasel - 28/5/20 at 10:28 AM

I'm using a heated screen as demist for the windscreen, and don't have a heater/fan. How do they test that it works at IVA?

I'd like to test that it works before installing the dash, so that I can easily get to the wiring if I need to change anything. Any suggestions on how I could test it would be really useful!

Thanks

gremlin1234 - 28/5/20 at 11:29 AM

one easy test would be connect it up and measure the electrical current draw.

I would use a clamp meter around the battery lead, without the engine running (so it isn't supplied by the alternator)

theconrodkid - 28/5/20 at 11:56 AM

when i did mine, he breathed on the screen and watched in amazment when the condensation dissapeared

Mr Whippy - 28/5/20 at 11:56 AM

it does get warm to the touch, my tin top has one

an hand held thermometer will also very clearly show it and is very handy in the garage anyway


[Edited on 28/5/20 by Mr Whippy]

nick205 - 29/5/20 at 06:42 AM

quote:
Originally posted by Mr Whippy
it does get warm to the touch, my tin top has one

an hand held thermometer will also very clearly show it and is very handy in the garage anyway


[Edited on 28/5/20 by Mr Whippy]




My wife's previous tin top had a heated windscreen and likewise got slightly warm to touch when switched on.

The huff test seems equally good to me as well.

The screen manufacturers will test them before they ship them, but will very likely use expensive calibrated kit to do the test.

Schrodinger - 29/5/20 at 07:49 AM

You can also see the elements in the screen, when Mine was tested I just turned it on and he put his hand on the screen and said 'That's fine'

wonderfulweasel - 29/5/20 at 09:20 AM

Thanks for the comments.

I've powered it up and the tell tale light on the relay comes on. The relay outputs also give 12v. The screen doesn't feel especially warm, but it is quite warm in the garage at the moment! So it may be that the ambient temperature is as high as the screen temp. I am using an oldish battery that's not been charged for a while, just as a tester.

Unfortunately, I don't have the equipment to test the current it's drawing, as I suspect it goes above 10A.

I think it is working, but I might give the battery a charge and use the hand test when the weather cools down!

indykid - 29/5/20 at 01:48 PM

I used a kettle of hot water to test the front and rear heated screens in my MX5 when I wired them up.

It's a fairly conclusive test as you can see the elements evaporate off the condensation and even see dead elements.

wonderfulweasel - 29/5/20 at 07:42 PM

Battery charged and...
It definitely works!
Activating one side at a time, the side that is on clears my misty breath much faster!

Thanks for your help