14 replies to this topic

[Midas Mk1]

Ive recently bought a heated front Windscreen from Moss, which I will be fitting later on this week when my Mini comes back from the paintshop.
I was wondering how people have wired theirs up, I prosume a relay is used, and was intending on using another heated rear window switch to operate it, any advice would be appreciated on how the wiring up process is done.


Thanks in Advance

Sam

Edited by Midas Mk1, 11 September 2010 - 07:24 PM.

[mk1leg]

Yes I fitted one to my mini.............



and I threaded the wires down through the screen vents...................



and wired them up through a relay via a heated front screen switch...............



good luck and be very carefull not to damage the 2 wires comming out of the middle of the glass...........

[Midas Mk1]

Cheers Mk1 Leg!

[Midas Mk1]

Bit of a bump on these thread, as Ive now got the screen fitted, and its time to wire it up. I have a few questions though:

What is the polarity of the two wires from the screen, as there are no identifing marks?

Have people used 30amp relays? if so, how are they wired, ie a normal on off circuit, or a timer or temperature controlled circuit?

Any help would be greatly appreciated

[SolarB]

I've got a heated screen waiting in my loft but I'm a few months away from fitting it.

The screen has resistive elements so there's no polarity. I'm not sure of the power required but the people who supplied it will know the current drawn. Some cars have a timer on the screens but I intend to wire mine to a relay activated from a switched 12V line. Wired in this way I can't leave the thing on when I leave the car.

[minidan]

hi guys, i have been trying to find info on this subject since fitting a minispares heated screen to my minus.

Can you tell me how many wires you have in total coming from the screen. i only have two.

i think some of the moss ones ( or all of them) have 3 wires). the middle one being the earth.

if so, why do i only have 2 wires? it would seems theres no earth wire in that case.

MK1leg - where is your screen from?

cheers .

[Dan]

The 3 wire versions simply have two smaller heating elements in them rather than one big one, you can switch each side seperately or sometimes I believe they are built so that the driver's side will run hotter sooner. No difference though, earth is still earth. As said above, the heaters are plain resistors and have no semi conductors so polarity is irrelevant.

Personally I think these should always be timed. By the time the glass starts to freeze up again, the heater will have warmed up enough to keep it clear. When it's on, if the alternator is standard the battery will take a hammering and won't be getting charged. With a timer, once the screen has shut down the battery can start to recover. Obviously you can remember to turn it off but the timer makes it a lot easier.

[minidan]

Dan do you know anything about the minispares heated screens? do you know how to wire up the 2 wires on the screen?

[Midas Mk1]

Thanks for the Replies!
Mine is a two wire one too , i have contacted both Moss and the manufacturer of the windscreen
http://www.heatedwindscreen.com/
but have yet to receive anything back from them.
So far ive got a 30amp relay, aswell as suitable wire, along with a second heated window switch, and Id like to fit a timer into this circuit. Does anyone have any tips how to create a timer for the screen?

Cheers

Edited by Midas Mk1, 23 October 2010 - 05:51 PM.

[Dan]

There shouldn't be any problem wiring these up, one terminal is live the other is earth. Doesn't matter which is which as said several times above! I can't see any other way that it might even be possible to do it.

There are several timer relays available from auto electrical suppliers, I use one for my rear screen that runs about 15 minutes. It came from Vehicle Wiring Products. It won't run 30 amps though so you can use it to control another, high power relay that powers the screen. Another advantage of this is you can make it only work while the ignition is on or the engine running, but still power it directly from the solenoid (through a fuse obviously) because of the two relays.
The timer needs a momentary switch, use a brake test switch and swap the front lens for one from a heated screen switch. When you hit the switch it starts the timer, then it will turn off and reset after 15 minutes, when you hit the switch again or when the ignition is switched off.

[minidan]

so is it correct that you can't use the existing wiring and switch for the rear screen and simply connect it up to the front screen instead?

[Dan]

Absolutely not, the rear screen draws 5 amps and that's what the system is designed for. Front screens tend to be over 20, you will almost certainly have a major electrical fire if you use the existing system or use a standard rocker switch without using a relay. It's the same as adding spotlights to the existing headlamp wiring, a really really bad idea.

Anyway, if you did that you'd have no heated rear screen which is kind of more important because there's no heater at that end of the car.

[minidan]

Thats ok, ( i said 'can't use' )

by the way i dont use my heated rear screen anyway as i dont have a rear view mirror.

[minidan]

one last thing on the subject, what is the most suitable wire to use?

[Dan]

Automotive cable, rated higher than the screen will ever draw, higher than any of the components used and higher than the fuse. If the screen is rated by the manufacturer at say 25 amps, you should fuse it to 30 amps continuous, use a 30 amp rated relay and probably at least 40 amp rated cable. Fuses can run at currents higher than their continuous rating for some time without blowing so there always needs to be extra capacity in the wiring, just in case.