Wikipedia:Reference desk/Archives/Miscellaneous/2015 November 21

= November 21 =

Car 'hood' and cold weather.
Good Morning. I have a megane convertible, in which the window drops down an inch before the door opens, and goes back up once closed. In below freezing weather, the window doesn't drop down, but the door still opens. It doesn't close though, until whatever inside the door is frozen has defrosted, so I can't drive until this happens. My question is would one of those big hood type things (that I assume are used to keep the windscreen ice free) actually help here? Thanks in advance.86.137.69.4 (talk) 09:59, 21 November 2015 (UTC)


 * It may not be anything frozen, just the coefficient of thermal expansion, applied to the material in the door and door frame. In that case, keeping it warmer would be one option, as in a garage.  Or a mechanic might be able to find whatever component has an improper clearance and adjust it so it can accommodate the natural expansion and contraction due to the weather.  (I will resist the temptation to suggest you buy a better car.) StuRat (talk) 10:33, 21 November 2015 (UTC)


 * The MINI Cooper (both convertible and hardtop) does the same thing - the window is 'frameless' and lowers a half inch or so to clear the seal that runs along the roof line. In the MINI, at least, the problem isn't with the cold per-se - it's with moisture on the outside of the glass freezing and making the window stick.   The MINI (and evidently in the Megane), there is enough flexibility in the system that the door will open with the window fully shut - it's designed to allow that so you can get into the car when the battery is dead (so you can pop the bonnet catch and charge the battery). But when you try to shut the door, the glass hits the sill of the roof.  I've heard of cases where people didn't notice the problem and slammed the car door hard, shattering the glass - so this is definitely not a good thing!


 * I'm not sure what our OP means by "those big hood type things" - if we're talking about the slot that runs along the base of the windscreen - or a 'hood scoop' then no, on most cars those are generally air intakes. I'm not aware of any mechanisms that would help this on any car I've ever seen - apart from the heater ducts on the inside of the car.  Running the heater on "defrost" while driving the car should help - but if the car has been parked for hours and thereby become frozen, then you can only resort to scraping any surface ice off of the window before attempting to open (and more especially, close) the door.


 * If (as StuRat suggests) it's not ice build-up, and just some component that's locking up in the cold - then I strongly suggest a trip to your Renault dealership. Probably there is some component of the window mechanism that isn't adequately greased, or perhaps there is some adjustment that has not been correctly made.  You may have to take the car there in cold weather and have them park it outside and have their techs look at it first thing in the morning so they can replicate the problem.  Use the dealership and not some other repair place - you need people who are experts in that specific vehicle and who have access to the manufacturers service bulletins.


 * If all else fails, you might consider getting one of those car covers to cover your car while it's parked...that will prevent moisture buildup...and if you have a cloth-top convertible that has to be parked outside, it'll considerably improve the life of the roof - even in summer.


 * SteveBaker (talk) 13:09, 21 November 2015 (UTC)
 * I assumed that by "one of those big hood type things" the OP was referring to "one of those car covers to cover your car while it's parked". Deor (talk) 16:25, 21 November 2015 (UTC)
 * You mean like this? -- Jayron 32 18:50, 21 November 2015 (UTC)
 * OP here, and thanks for replies. Yes, like that, but I've only seen ones that cover the top half of the car.  The manual refers to not closing the door when frozen, so not a mechanical fault with this car (although rather a design fault with this make, at least for people who buy them where the winter can be below freezing.)


 * So will one of these covers keep the car 'warmer'? Will it help at all?86.137.69.4 (talk) 22:17, 21 November 2015 (UTC)
 * Well, it does indeed helps to stop frost forming on the windscreen (which is why I use one when necessary), so probably yes.
 * When the car is parked under a clear sky, it's radiating heat, but is getting very little radiated back fron the sky, which is a bunch of air mostly below zero C underneath a bunch of space not much more than zero K – this is why frost can form on the windscreen even when the ambient temperature is above zero C. The cover however remains at ground-level ambient, so is radiating a little heat back at the car. (This is also why one may find that the side windows facing a building don't frost up when the other side facing the open does.) There's probably also a minor element of reducing convection and retaining some residual heat from the slowly cooling engine. {The poster formerly known as 87.81.230.195} 94.11.50.58 (talk) 22:58, 21 November 2015 (UTC)


 * I wonder if glowplugs can be installed in a door. StuRat (talk) 19:22, 22 November 2015 (UTC)