Wiring the Td5 rear door to a 300Tdi

technical

If your vehicle is made post-2002 then the wiring loom will connect straight away. If you are putting the door on an earlier vehicle, it will require a bit of fiddling because the connectors are different and the newer door's wiper is negative switched whilst the older door's wiper is positive switched.

I will refer to the pre 2002 system as 300Tdi and the post 2002 system as Td5.

There are a three options on how to wire up the door:

Use the wiper wiring from the older door on the new one
Use the wiper switch system from a 2002 dash
Keep both old and new systems and adapt to fit each other

I went for the third option, being the cheapest whilst keeping the more modern door loom for possible fitment of the matching dash later on.

The tale of two looms

At first glance the systems appear incompatible as the 300Tdi system uses 4 wires for the motor and the Td5 system uses 3 wires. This is because in the Td5 the wiper park relay and "logic" is dealt with in the door loom, as opposed to in the dashboard. Although the two systems are be compatible because the wiper motor is the same part number through all the years (AMR3676).

What this means is that the Td5 wiper set up has constant power and when the switch is earthed, the relay routes the power from the ignition feed to the motor and the wiper starts. When the switch is turned off the relay changes the motor feed to another ignition feed, which then turns off when the wiper gets to the park switch.

The 300Tdi wiper wiring loom is powerless until the switch sends power to the loom on the Red/Light green wire and the wiper starts. When turned off the switch gives power on the Brown/Light green wire until the wiper parks and the park switch disconnects this feed.

So with the 300Tdi switch we will be controlling when power goes to the system, but of course if we turn the switch off the motor will stop. So we have to route a new wire from the constant ignition to the +ve feed to the park switch so that will work when the switch is off.

If you're still following me, then you're doing well. It took me about two hours to work it all out! The wiring colours on the loom connectors for the two systems are as follows. Please see the official connector information at the bottom of the page for a more detailed breakdown.

300Tdi wiring colours		Td5 wiring colours
Black	Earth	Black	Motor earth
White	Heated screen +ve	White/Black	Heated screen +ve
Red/Light green	Switch to Wiper +ve	Green/Purple	Centre stop light +ve
Brown/Light green	Park switch +ve	Black/Green	Motor switch earth
Green	Ignition	White/Green	Ignition

NB: Please make sure you read this through and make sure that you are happy with what I have done. The procedure is simple, only requires one alteration to the Td5 loom, and I can vouch that it works but please take a look at the wiring diagrams (below) and make your own mind up as i'm not a qualified electrician!

What you'll need

New 6-way multi connector
A bullet connector or equivalent
Some White/Green thinwall cable

Cut or disconnect the existing loom and with a new multi connector, link up the following items.

Heated screen element

This can be wired up directly by connecting the Td5 White/Black with 300Tdi White.

CHMSL

Having a centre high mounted stop light will require extra wiring, which I won't cover here as I don't have one.

Wiper motor

To link the two wiper systems, do the following:

Connect the Td5 door White/Green to the 300Tdi Red/Light green (Fig 1 & 2)
Connect the Td5 Black & Black/Green to the 300Tdi Black (Fig 1 & 2)
Run a new wire from the 300Tdi Green to the Td5 White/Green running from the Relay to the Wiper motor park switch connector. Insulate the floating White/Green wire (Fig 3 & 4)
Insulate the 300Tdi Brown/Light green and tie away

With this wiring configuration, the switch tricks the ignition fed relay on the Red/Light green wire by switching the ignition feed instead of the earth. When the switch is turned off, the relay will switch power to the new Ignition wire until the wiper parks and all connections are cut.

And that's all it should take to get the rear wiper working. I'm sure the system is more refined when connected to the rest of the post 2002 wiring system; currently, the motor pauses slightly when the switch is turned off and the relay moves feed, but it does the job without having to rewire the whole Defender!