Fuse box internal connection

[ArthurH 7]

I appreciate that this is a difficult question, but if someone out there does have the answer, it will save me hours of dismantling and testing 

 

My son's 205 CSH race car is obliged to run the original loom and hence fuse box.  The person that originally built the car repurposed an existing wire that ran to the back of the car to power the rain light.  It uses the original fog light switch on the dash which seems not unreasonable but the repurposed wire might not be a fog light wire, it could be any of the various devices that are no longer present (rear wipers, washers, etc).  Unfortunately, the rain light stopped working at Silverstone last weekend and I'm struggling to find the fault.  I have identified which wire from the light it is that is plugged into the fuse box (see photo).  If I send 12v down the wire from this point to the back of the car the light works.  However, none of the five connections on the back of the switch 'buzz out' to the same point on the fuse box - which is probably where the fault lies.  It would help me greatly if I knew which wire goes from the fuse box to the switch.  Can anyone tell me which wire is the one that connects up to the thick white wire that I am pointing at with the screwdriver in this photo?  It is the second from last slot in the single row plug at the top of the fuse box:

 

 

 

TIA :-)

 

 

 

[309SRiguy 15]

It looks like it is the G plug/socket that you are pointing to.

 

This link has diagrams that might help you trace the circuit you need. 

 

 

[ArthurH 7]

Thanks Bryan.  Yes, it is the penultimate slot of the G plug.  Can I assume the numbering is from left to right?  If so, it will be G9 that reappears as D2?

 

I guess I don't need to know, but would anyone know what this circuit originally supplied?

 

Thanks

[ArthurH 7]

I wrote the previous note as soon as I read your reply this morning.  At the time it all made sense....     However, I have now checked the car, and I am even more baffled 

 

D2 (&D3) have the stubs of chopped-off green wires; so they were never used as part of the connection to the rain light switch.  I then wondered if the numbering of the sockets was from right to left (like a consumer unit?), which would mean that it is G2 rather than G9 that has the thick white wire that goes to the light.  If so, the connection would be to P3 - But I can get detect any continuity from G2 to the P socket at all.

 

I'm at a complete loss - any ideas?

[309SRiguy 15]

They run 1 to 10  going right to left on the top of the board. Left to right on the bottom of the board.

[309SRiguy 15]

They run 1 to 10  going right to left on the front of the board. Left to right on the back of the board.

[ArthurH 7]

Thanks Bryan.  That confirms that the plug connector I am pointing at in the photo is G2 and not G9.  According to the diagram this goes to the 760 relay, can I assume from that, the thick white wire is the supply to the heated screen ?  It also goes to P3 and Y1.  There is a thin blue wire connected at P3 - but I can't get any continuity to G2   However, and this is the first success!, I do have continuity between G2 and Y1.  Y1 is a single connector plug, and sadly there is nothing plugged into it.

 

If the rain light is not only passing through the fuse board, but making use of the HRW relay (and why not?) then perhaps it is a failure of this relay that has caused the problem?

[ArthurH 7]

Thanks to the diagram supplied by Bryan, I have sorted out the fuse box aspect of my problem, so thought it appropriate I'd bring this thread to a close.  It turns out that the original builder of the race car had used the heated rear screen wire AND relay to operate the rain light.  The relay may have been overkill as it is a low wattage LED light, but I can see the logic.  If I provide 12v to P2, the relay and hence the light works.  The remaining problem is that the light switch isn't providing that 12v, nor, by the wiring can I see how it ever did!

 

I now need to know the internal wiring of the fog light switch - but I'll open a new thread for that.

[SRDT 186]

The circuit they used is the only one that regulary fail on those fuse box: