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ibexman



Member Since: 13 Dec 2008
Location: kent
Posts: 2871

United Kingdom 
Heated rear window wiring for windscreen
I rarely use my HRW. I was wondering if it could be utilised to power a front heated screen , any thoughts appreciated cheers Chris
Post #944238 1st Mar 2022 1:00pm
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Cubflyer



Member Since: 25 Sep 2021
Location: Suffolk
Posts: 278

United Kingdom 1994 Defender 90 300 Tdi SW Arles Blue
Nice thought Chris ... cracking idea Exclamation

Hopefully comments will come flowing in, personally can't see why it wouldn't work Question 2010 Defender 90 300Tdi CW (White/1994)
2021 Defender 90 300Tdi SW (Blue/1994)
Post #944239 1st Mar 2022 1:14pm
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ibexman



Member Since: 13 Dec 2008
Location: kent
Posts: 2871

United Kingdom 
Hopefully 👍
Post #944242 1st Mar 2022 1:22pm
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Race.it



Member Since: 27 Aug 2019
Location: Algeciras
Posts: 739

Spain 2010 Defender 110 Puma 2.4 SW Alaska White
is not the front one on a timer? dont think the rear one is? Searching for my first Defender...and started just as Covid hit, so talk about timing.

5 months after starting the search I found it, and here is the details
Post #944244 1st Mar 2022 1:33pm
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Penfold_6290



Member Since: 22 Sep 2021
Location: Dorset
Posts: 272

United Kingdom 2002 Defender 110 Td5 CSW Epsom Green
It’s possible but you’d want the switch to trigger a timer which in turn powers a relay (big one, 70 amp). The HFS shouldn’t be left on permanently, you will burn out the elements. Mine is on for 7 minutes which is ample. You can easily source a timer for this but they aren’t rated for the current drawn by a HFS, this is why the 12v output from the timer energises the coil of the appropriately large relay.

There’s no reason why you couldn’t leave the HRW wiring in place and piggy back a feed from the white/black wire to the timer. That way you could have both on at the same time. If you don’t want the HRW you can just push the switch again to cancel the HRW. The HFS draws high current so use some appropriately sized cable to cope with the load and the same for the earth.

The proper factory solution interacts with the oil pressure switch so you can’t have the HFS without the engine running. If you’re going to use the latching HRW switch you’d need to be careful that you don’t forget it’s ‘on’ when you are starting the engine, then you’ll be trying to crank the engine while the HFS is consuming watts at an alarming rate.
Post #944247 1st Mar 2022 1:36pm
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