Hi all, I've just had autoglass put a new front windscreen on my focus, and I was talking about the heating element guarantee because if it's not frosty until next winter it's going to be difficult for me to check it works properly. So he said if the glass is frozen it shouldn't be used until the blower has warmed up the glass. So I said to him that it automatically comes on if it's cold enough (same on my mondeo), he reckoned it shouldn't!? Does yours? And if it does what are your thoughts on this?

Mine doesn't come on automatically but I use it when window is frosted up with no problem you'd have to warm the car up first to use the blowers like he suggests which really is defeating the object of having the heated screen .

Well that's what I thought, he said he gets no end of broken rear screen in the winter due to people using the rear demister straight away, more like people throwing boiling water on it i think

Both front and rear screens come on auto below a certain temp, think its around 2 to 4 c. Doesnt show up on switches that there on,

if it was an issue then ford wouldnt have them come on auto

I've never had any issues with auto - on heated screens in over 24 years, dating back to my 1991 XR3i & several other different Ford models since & my switches always illuminated when on.

auto heating when cold is an option in elmconfig, as for it breaking windows when not frosty, I seriously doubt that, its such a low amount of heat being applied, its sure as well not as hot as hot water or even a hair dryer.

to test, fill up a kettle, boil it, and sit in the car for a few min, whack on the demisters and watch it vanish :)

the heated screen warms up gradually so it wont crack the glass its not a sudden heat if you want to test its working put a cup of hot water on the dash for a minute then test the screen