Ahh, it's not there? That surprises me.
It is quite a big thing (250mm x 100mm x 35mm) so shouldn't be hard to find if it's there.
Scott, finally had chance to look for the main board tonight. Being an R500 there is spare room behind the dash on the passenger side. It is situated here. All the plugs look well seated and the board looks fine. I would love to know who made it for Caterham and what the 9 pin D type plug is for, assume some sort of test rig connection?
The D-Sub connector will likely be for flashing the processor.
Do you hear a realy klicking when the car won't start? It could be one of those that has started to fail. Unfortunately it looks like it's all glued in some sort of epoxy and therefor extremely difficult to repair.
Blatchat Google Search
The boards are heavily filled with potting compound, it's hard to see how you'd dig out any particular component, even if you knew which was faulty.
Car will always start but will not always stop. If I stall the engine the dash sits there lit up and making a buzzing sound but the start/stop button fails to turn off the ignition. The immobiliser seems to be working fine and as expected. All other switches seem to function ok when driving. If I disconnect the battery and reconnect then the ignition remains off and I can restart the car, but then have problems switching off again. At the weekend I drove to Compton Abbas for breakfast. Car would not turn off there so disconnected battery and reconnected, this was after fitting the new start switch. Drove home and same thing. I am wondering if the problem is related to the lights being on or heat as I have popped to get fuel without the lights on and it has worked fine.
That could be a relay that has started welding the contacts. You could tap the top of the relays when it won't stop and see if anything happens. Tap IE with the handle of a screwdriver.
There are 14 relays on the board, gonna be lucky to find which one is sticking.
But still it would indicate that it's the relay unit that's faulty, and as you presumably can't replace a single relay due to the resin, then you just want to know there is a fault ;-)