Yes mate. Im not mechanical and have no idea about the way a car or its electrics work. I am learning tho
Exactly, everyone has to learn at some point. Well done for trying.
The starter will probably be earthed through the engine... The battery basically has a wire going from the negative battery to the car's chassis/body. So the whole car becomes a earth 'wire' going back to the negative pole. The engine is metal and bolted to the chassis, so that to becomes an earth. The starter's bolted to the engine....
I missed a bit on the wiring diagram, the wire from the ignition switch goes to the F5 fuse in the passenger compartment, that them also goes to the Start Motor Solenoid Relay...
If you're not sure what a Relay is, I'm probably not the best to explain, but basically they are a switch - in this case a switch to turn on power to the starter motor solenoid. Instead of a push button (or rocker switch etc) they use power going through another wire to switch it on or off. It gives 2 benefits that I know of - (1) you can put 'logic' on the switch wire so that it becomes a 'clever' switch and (2) you can safely put a lot of current (amps) through the power wires while keeping the switch wire a current (eg you don't want 30amps going through the ignition switch).
I missed a part of the circuit diagram. In the engine compartment fuse box there's a link to a wire to the ignition switch. The 'crank' position has the WR wire going to Fuse 5 in the passenger compartment fuse box. From there there's a WR wire to the Starter Motor Solenoid Relay.
So the Starter Motor Solenoid Relay 'switch wire' is fed from the ignition switch via the passenger compartment F5 fuse. It is earthed to the CCU. I imagine the CCU open's this earth if the imobiliser says its safe to start the car. So with the ignition switch on crank and the CCU set to safe - there will be a current through that will 'turn on' the Relay.
The 'power' feed that is turned on from the Relay comes from the battery via your tripping F1 fuse in the engine compartment to the Relay and from there to the Starter Solenoid on the Starter motor - and is earthed through the engine.
Give that F5 is not blowing, the switching circuitry is all working well and has been protected from damage by the Relay. You can therefore disregard the fuse box in the passenger compartment - unless someone else thinks otherwise.
There's 2 power feeds to the Starter Motor, the direct feed from the battery (no inline fuses or relays) is the main one that actually turns the motor. The other one (which goes through F1 Fuse and the Relay) engages (turns on) the Solenoid that actually turns on the main feed.
If you had disconnected the Solenoid feed and jumped a wire directly from the battery to the solenoid - then I really don't know how Fuse 1 could have blown. You would have had direct live connections to solenoid and motor and direct earths through the engine/chassis. All the car's wiring would have been bypassed.
The only things I can think of is corrosion or an earth around the F1 fuse or an earth in the wire from the F1 Fuse to the Starter Relay.
I'm no where near an expert in these matters. Hopefully you can understand a bit more from my ramblings and I haven't lead you up any garden paths!
