Help re-wiring Ignition Switch (Lucas 162SA)


New member
1985 Defender 90 ROW with other prior owners and a patch work of non-OEM wiring.

In an effort to resolve a “no start / no crank” situation, I removed the Ignition Switch (Lucas 162SA aka PRC2735) and when pulling out the heavy lock barrel, I accidentally dropped the piece and most of my wires came off before I could take a picture of the corresponding terminal # and wire colors on my truck.

I’ve ordered a replacement PRC2735 given this part of the truck is apart and the replacement seems a reasonable preventive maintenance investment. I can’t test whether the existing switch was failed because I am unsure which wire colors correspond to Terminals 1, 3, 4 and 5. For what its worth, Terminal 2 (a 10mm spade) stayed connected to an Orange wire, which based on searching this site, should be the Glow Plug Feed. Also my truck was only using 4 Wires, so there is an extra terminal on the Ignition Switch which must not have been used.

Is it possible to solve this puzzle; (1) based on the Gauge of the wires that are disconnected and coming out of the dash and/or (2) the disconnected Wire colors and there corresponding gauge:
-Brown 12 Gauge (6mm spade)
-Red & White 12 Gauge Wires Joined on the spade connector (terminated with single 6mm spade)
-Red/White (a single wire with two colors) 16 gauge wire (6mm spade)

# - Purpose/Feed Wire Color

1 – Ignition (6mm) - ??????
2 – Glow Plug (10mm) - Orange
3 – Fuel Solenoid (6mm) - ??????
4 – Starter (6mm) - ??????
5 – Perm 12v (10mm) - ??????

I would appreciate any help or advice to match-up the correct Switch Terminals to the correct wire feeds on my truck.

A picture of what I’m looking at:


  • ignition switch.jpg
    ignition switch.jpg
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New member
Another question and some information. I have confirmed with a volt meter that the Brown wire (12 gauge) is carrying 12v (constant w/out turning key etc.), so this will be connected to Terminal 5 on the switch (input). Since Terminals 3 and 4 are outputs , does it matter if the Starter Solenoid and Fuel are incorrectly wired to either of these switch outputs? If I put this back together and turn the ignition, with the fuel and starter wires “reversed” (trial and error) ... is this a bad idea?


New member
Thanks for the replies. I used that Lucas 162SA picture to label the feeds in the matrix found in my picture. I hope this is how my nonOEM wiring (colors don’t align with the attached manual) was been applied in my truck.

I will work through the feed testing process to determine the 16 gauge wires that were connected to the Ignition, Fuel and Starter outputs.