Rear window demister

Guys, this may be a stupid question, but I'll ask it anyway.

What is the amperage of the rear window demister on late model GU's? I have never had the need to use the rear demisters on any vehicles I've owned, as I find that the AC does it better. That said, I have also never turned off my AC in any vehicle I've owned. Never had a bearing failure or gas leak as I'm sure it's the constant use that keeps everything lubricated.

Anyway ......... I'm considering using the demister circuit to power a flashing LED warning light bar, a requirement on vehicles on construction or work sites. The light bar is about 12" long with 16 3w LEDS. There is no rating label on the light bar.

I'm considering locating the light internally high on the glass on one of the rear doors.

Can anyone see a problem with this assuming the circuit amperage is sufficient?

The rear demister runs through a relay so it will be able to handle the load of the light bar. The problem is every time you turn the vehicle off you will need to turn the light bar back on and it's a timed circuit after X amount of time it automatically switches off.

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Originally Posted by Yendor

The rear demister runs through a relay so it will be able to handle the load of the light bar. The problem is every time you turn the vehicle off you will need to turn the light bar back on and it's a timed circuit after X amount of time it automatically switches off.

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Thanks mate. Forgot about it being a timed circuit. New plan. Maybe the rear cigarette/ accessory socket, if I rewire it to a permanently live circuit, or the existing fridge circuit.

The rear accessory socket can easily be changed to a permanently live circuit. There is a relay mounted in the LHR quarter guard you could just bypass. But how would you switch the light on and off?

Quote:

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Originally Posted by Yendor

The rear accessory socket can easily be changed to a permanently live circuit. There is a relay mounted in the LHR quarter guard you could just bypass. But how would you switch the light on and off?

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The light bar has a sequencing & on/off switch already wired to it.

You will need to remove the trim from the LHR quarter. The relay is located at the front of the quarter panel near the seat belt retractor for the LHS second row seat.

Unplug the relay and either join the Green with a Red trace wire to the Blue with a White trace wire or make up a little bridging strap with male crimps at each end and simply plug them into the relay base.