FYI - heated windscreen draws 35 Amps !

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Propshaft
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FYI - heated windscreen draws 35 Amps !

Post by Propshaft » Sat Dec 03, 2016 3:35 pm

Hi, folks,

before wiring the new heated screen I was interested what current goes through the cables.
Each side of the screen draws around 17,5 amps = 35 amps in sum

Okay, 2 relais needed, switch separately.
Happy to have a 55 A Bosch generator installed. Will connect this directly to the relais, fused of course.

And good thing is that the screen gets handwarm after three minutes :-)

cheers!
Michael



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Re: FYI - heated windscreen draws 35 Amps !

Post by scimjim » Sat Dec 03, 2016 4:41 pm

The manufacturer does specify 25A per side and two relays (but no need to switch separately), so that's not totally unexpected - although it should drop with time as it heats up?


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Re: FYI - heated windscreen draws 35 Amps !

Post by td99 » Sat Dec 03, 2016 4:42 pm

Propshaft wrote:Hi, folks,
And good thing is that the screen gets handwarm after three minutes :-)
And fries eggs in 5 mins? :D :D :D


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Re: FYI - heated windscreen draws 35 Amps !

Post by Corky » Sat Dec 03, 2016 4:47 pm

The one I fitted to the DET racer dropped about 100rpm off the engine speed when switched on. I don't now about 35amps, I'd put it at about 20BHP :lol:


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Re: FYI - heated windscreen draws 35 Amps !

Post by Propshaft » Sat Dec 03, 2016 5:19 pm

scimjim wrote:The manufacturer does specify 25A per side and two relays (but no need to switch separately), so that's not totally unexpected - although it should drop with time as it heats up?
I wrote to the manufacturer but he has no numbers about amps thus I put my Digimeter between the wires.
The manufacturer is right to recommend 25 A fuses per side as 17,5 amps is drawn.
I will switch separately as I only need drivers side to be cleared first. After this I can switch to passengers side.
No, there is no dropping of amps as the screen gets warm.

cheers!
Michael



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Re: FYI - heated windscreen draws 35 Amps !

Post by Propshaft » Sat Dec 03, 2016 5:37 pm

td99 wrote:
Propshaft wrote:Hi, folks,
And good thing is that the screen gets handwarm after three minutes :-)
And fries eggs in 5 mins? :D :D :D
not to imagine the smell if all the insects, guano, porridge and pie burns to coal .......



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Re: FYI - heated windscreen draws 35 Amps !

Post by toomanysabres » Sat Dec 03, 2016 7:53 pm

You're supposed to wire the two sections in series not in parallel so you will have 8 amps.
Parallel operation is only recommended for say a stage rally car where you want it cleared super quick and is only on for a short time.
If on for any length of time it will compromise the plastic layer in the thickness of the screen.
My Coupe one takes 8 amps.


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Re: FYI - heated windscreen draws 35 Amps !

Post by peter freeman » Sun Dec 04, 2016 10:39 am

I fitted a heated screen to my 6A when I had it and found that a large proportion of the elements did not work. Our main problem is that our cars are parked on the north side of our house and therefore never see the sun. The best resolution to clearing the ice off the car glass is to use a fan heater which I place in the car 5 mins before we set off. This means that the glass is free from ice and the inside of the car is nice and warm and it cost less to run a fan heater than it does to run the engine until it is hot enough to de-ice the screen. The fan heater has a switch on the bottom to stop it should it fall over - it never has.



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Re: FYI - heated windscreen draws 35 Amps !

Post by toomanysabres » Sun Dec 04, 2016 1:47 pm

OR and I can't seem to get this over to neighbours who constantly scrape the windscreens and that is to pour a kettle full of cold water over the frost. By definition tapwater is many degrees warmer than frost.


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Re: FYI - heated windscreen draws 35 Amps !

Post by Propshaft » Mon Dec 05, 2016 12:36 pm

toomanysabres wrote:You're supposed to wire the two sections in series not in parallel so you will have 8 amps.
Parallel operation is only recommended for say a stage rally car where you want it cleared super quick and is only on for a short time.
If on for any length of time it will compromise the plastic layer in the thickness of the screen.
My Coupe one takes 8 amps.
Thanks for that hint!

I will do a "clever" combined wiring with two relais and install a two mode running:
- start first mode with full power to the drivers side of the screen = 17,5 Amps
-after defrosting / defogging I will switch to full screen in series mode = 8 amps

cheers!
Michael



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