How to wire a heated rear window switch

[Clydebuilt]

Hello,
Does anyone know how to wire up a new rear windscreen which has the heating elements in the glass?
I bought a new rear screen a few months ago from Custom & Commercial in Bookham Surrey, but they and everyone I've asked since I bought the rear windscreen don't know how to wire it up.
I bought the suitable wire from Heritage Parts and got hold of an original (working) dash switch.
I've been told it goes from the left side of the top of the tail gate down to the front left cab door and to the fuse box which - on my bus is on the front left of the cab, as my T25 is a RHD.
No one seems to know how to wire it up.
Can anyone help me out please?

Kind regards
Christopher

[Mocki]

the original loom goes along the top and down the n/s "A" pillar to the back of the fuse box, via a relay ( position 11 on a late van ) and across to the dash. the neg just earths next to the window on the tailgate.
fuse box is the same side on all lhd and rhd i thought


why is this in mo??
ill move it to electrical

[Clydebuilt]

Thanks Mocki,
I didn't know there was an electrical questions section.

When you say the "wiring goes along the top", where exactly is "the top" and any hints about getting the wire along this section?
Cheers
Clydebuilt

[Clydebuilt]

I forgot to ask you Mocki,

I've got an '87 van, is that considered "a late van" and where/what is "position 11"?
Cheers
Clydebuilt

[Mocki]

Ok, sorry fuse 11 .
Up along the top skin of the van , above the interior lights there is a channel that runs front to back both side of the van .

Basically unless you have the original loom it’s just the same as wiring up aux driving lamps , but the heated screen instead of the lamps , same basic relay circuit , with the trigger wire for the relay being switched by the HRS switch from a ignition on live and the power taken from the fuse box

[Clydebuilt]

Mocki,

You didn't answer my question. "I've got an '87 van, is that considered "a late van" ?

Thanks
Clydebuilt

[Mocki]

Sorry , yes , 85 onwards is late , blade fuses and short sliding door handle

[what2do]

You'll need to 'fish' the cable down the A-pillar. I used electrical 'fishing' rods up the A-pillar (push up from beneath the dash) until it poked through and was visible. To ease the process, remove the grab handles first, my rod kept hitting the screw which protrudes into the pillar. Once you the rod is visible, tape some nylon line to it and pull it through to the footwell and discard the rod. You are now in a position where you can draw the loom through by taping it to the nylon line.

You'll need to do the same through the roofline but this is a much easier process.

It's the same relay that is used for the heated mirrors so you may as well fit them whilst you're at it