Brown Wire Fix

After further troubleshooting of the no start issue I came to the conclusion that the "brown wire" fix was the way to go.

I don't really understand why but this is how I decided. The voltage at the battery is 12.32v and the voltage on the thick black wire going to 30/1 on the ignition switch is also exactly 12.32v - so no drop from the battery. But the brown wire reads 11.34v. That's almost a 1v drop. This reduced voltage seems to be insufficient to actuate the starter solenoid. The solenoid needs at least 12v. I proved this by touching the red starter solenoid wire with the brown wire, and then with the black wire. As soon as I touched the black wire the starter kicked in.

Given that the black wire and brown wire physically attach themselves together with the +ve battery connection on the starter stud I can only assume the 1v drop is between the starter and the ignition switch. But according to the wiring diagrams there is nothing between those two points for the brown wire. So I don't understand why there is a 1v drop on the brown wire when the black wire it shares the loom with has a 0v drop (I've obviously cleaned all the terminals with a metal file till they were all nice and shiny).

I didn't feel like taking apart the dashboard and rewiring the whole thing so I decided to just run an extra 10 AWG brown wire myself a.k.a the "brown wire fix".

As part of the main harness grommet on the firewall, there is a moulded covering for an existing hole. Its a little difficult to see but I've put a steel wire though it in this photo. It can just be pushed through.

I left the original brown wire disconnected at the ignition switch. I don't know what's causing the voltage drop so I should probably disconnect it at the starter as well. I connected my single new brown wire to #30 on the ignition switch and voila everything was working again - the car started instantly.