The connection between the engine loom and the chassis loom is easy to identify and simple to connect, but before I made this connection I tried ensure all the wires are routed as cleanly as possible.
Route wires as required 
Connect Engine loom
I removed a few factory tie wraps and replaced them when I had all the wired where I wanted them.
Engine and Chassis loom connected, note factory tie wraps removed and replaced as needed
Finally I connected the starter motor, the factory marked the stater wire with an S. Don’t forget your IVA nut cover.
Starter wire has S on it 
Starter connected 
IVA nut cover
There is still work to be done in this area with the battery and earth connection.
Tools Used
- Side Cutters
- End Cutters
- 13mm 1/4 drive socket
- 10mm 1/4 drive socket
- 1/4 drive ratchet
caterham420detailedbuildblog.co.uk 
[420R S3, Q1 2022]. There is so little room around the loom in the S3 that I routed the starter wire around the back of the battery, holding it in place with a pair of p-clips ((c) Chris Collins) on the rear bolts which connect the battery holder to the chassis.
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Hi Chris – you have 1 wire from the alternator plus the Red starter wire attached to the starter motor – is that all is required ? Caterhams manual says I should be connecting 2 additional brown wires from the chassis loom (both in a black sheath) to the same terminal but I can’t find them & the threaded post on the motor looks like it has no more room for more connections. I checked with Caterham Darren is on leave but Tony says there should be another 2 brown wires. Just wondering if there have been updates I am unaware of
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Hi Alan, you only have the brown wires if you don’t have a battery isolator. Your find the two brown wires connected to your battery isolator, so no need to worry about them. Hope this helps.
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Thanks Chris that makes sense – CC didnt point that out today ! Much appreciated
Alan
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