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Dick

Member Since: 06 Jul 2023
Location: London / Devon
Posts: 57

Wiring for dummy’s

I’ve managed to rewire all lights, remove and completely strip dash and rebuild with everything plugged back in and re-wired apart from one thing:

An aftermarket heater blower switch. Very basic on/off toggle.

Don’t know the history behind why this was added to the car, perhaps a cheap alternative to replacing other parts.

2 wires leading to the switch, marked + and A.
I believe they’re symbolic of += power source A = accessory or in this case, the heater blower.

I have traced one of the wires that was plugged in to this toggle switch back to the heater blower under the bonnet and connected that spade to the A tab.

I’m now left with the other (power?) wire and where to connect it?

Questions:

1) are my assumptions about the wiring above correct
2) of so, what can I tap in to behind the dash to connect the second wire?
3) if my assumptions are wrong, which tab should the wire traced back to the heater blower connect to and where should the other wire be going?

Many thanks!

22nd Jul 2023 10:04am

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6611

2015 Defender 90 Puma 2.2 XS CSW Montalcino Red

The original heater blower/fan wiring looks like this.

Click image to enlarge

There's a three-position switch (off, slow, fast [less slow!]). This works by switching a path to ground on either the green/yellow (slow - goes via the resistor in the fan assembly) or green/grey (fast) wires.

Are you missing the original left hand side sliding fan switch on the instrument binnacle?

Assuming you are to continue with the aftermarket switch and the original green/yellow and green/grey wires are still in place, you want to connect + [input] to whichever of those wires you want to use (slow or fast).

Connect A [output] to the black wire which should be the same size (cross section/diameter) as the green/yellow and green/grey.

1988 90 Td5 NAS soft top

2015 D90 XS SW

22nd Jul 2023 10:14am

Dick

Member Since: 06 Jul 2023
Location: London / Devon
Posts: 57

It looks like the green wired connecting the heater are still in place.

I think the white wires / switch are a replacement for the sliding 2 speed dash switch replacing with just on or off.

Will trace those Green wires in the hope they’re still connected to soemthing to connect in to finish this circuit, although it looks like the toggle switch is already wired right in to the relay before the heater matrix:

Click image to enlarge

22nd Jul 2023 10:27am

Dick

Member Since: 06 Jul 2023
Location: London / Devon
Posts: 57

Green wires are all still in place.

Looks like a new motor on the bottom of the heater unit which has been wired straight to that switch on the dash.

My guess is the old motor and speed selector has given up and rather than replace the whole blower unit a new blower fan was added.

Still nonethewiser where the second white wire should be routing to - is it just a ground/earth?

Looks like the new blower motor has power to it from red/black

Click image to enlarge

22nd Jul 2023 10:43am

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6611

OK so it's not standard at the blower end!

Without seeing the wiring of the bottom of the relay (curious as to the 5 wires to a 4 pin relay..) but you won't damage anything by connecting your loose ring terminal incorrectly, it won't short out anything it just won't work.

It is likely, as it's a ring terminal, that it's intended to go to a ground point behind the dash - but that is an educated guess not a guarantee.

The wiring of the bottom of the relay will tell you if the white wires is intended to be switched to ground or 12V to trigger the relay.

1988 90 Td5 NAS soft top

2015 D90 XS SW

22nd Jul 2023 11:32am

Dick

Member Since: 06 Jul 2023
Location: London / Devon
Posts: 57

Yeah it looks annoyingly cowboy.
Another thing to add to the list- replace blower and switches 😂
Will try grounding it and see if it works as that seems the most likely explanation as to why I can’t find where it came from - was probably hooked through a bolt and came off as I was undoing one of the eleventy billion

little fixings that hold the dash together!

So will ACC go to ground or + in this case?
Or just trial and error?!

22nd Jul 2023 12:30pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6611

It won't matter which way round the + and A go, as you're not using the LED in the switch.

But it would be good practice to do + to the wire going off to the relay, and A to ground.

1988 90 Td5 NAS soft top

2015 D90 XS SW

22nd Jul 2023 12:32pm

Dick

Member Since: 06 Jul 2023
Location: London / Devon
Posts: 57

Thank you good sir!

Will let you know how that goes!

22nd Jul 2023 12:34pm

Dick

Member Since: 06 Jul 2023
Location: London / Devon
Posts: 57

Earthed it and all good.
Revived the asthmatic wheeze back to its former glory!

Thanks for your help Martin!

22nd Jul 2023 4:06pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6611

1988 90 Td5 NAS soft top

2015 D90 XS SW

22nd Jul 2023 5:42pm

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