Just wanted to confirm that I have fixed the demister.   The problem was in part, how to avoid fouling the wiper mechanism under the dash, and also how to fix the tube to the underside of the vents.

Problem one was solved by moving the vents as far back as possible within the constraints of the bracket holding the windscreen (solved another issue by drilling out the thread in the bracket and bolting through – much more convenient).   Problem two simply expressed is how to fix the tube without being able to get to the underside to do up the bolt.   Solution – drill a hole directly underneath to take a socket on an extension, hold the nut with bluetack in the socket and voila!  Just need to tape over the access hole and it all works.   Took ages to work out and no time at all to implement!

While working on the demister, I took the opportunity to scope out putting a pull switch on the handbrake.  This is necessary to be able to show when the handbrake is pulled up, and, for the IVA, to show that the brake fluid warning lamp works.  This requires a little bit of wiring – effectively to short the brake fluid master cylinder switch and therefore light the lamp, when the handbrake is on.

I also took the opportunity to fit a combined rear fog and reverse light.  It is LED and looks fairly discreet above the number plate.  Regulations from 2013 require that the rear fog light may be switched on when the headlights are on, and must go off automatically when the headlights are turned off; and then may not come on again until the fog light is switched on again.  

The intention is to prevent leaving the light being active again on returning to the car and driving off in fog free conditions.  Car Builder Solutions do an electronic box that handles the latching and unlatching of the circuit and I will be wiring that into the circuit.

I am also investigating making an inductive proximity switch that will latch on when the gear shift lever goes to the reverse position and then off again for any other gear.  This would then operate the reversing light automatically removing the need for another switch on the dashboard.  It also avoids the need for replacing the rear of the 2CV gearbox to a newer version that is capable of taking a proper reversing light switch.

Watch this space…