Rob,
in that case, the wiring on your car must be unique, since every 2CV (and most other type of A series) which I've worked on has had a separate set of four connectors for its nearside and offside front lamps, with each set having its own earth.

Identifying colours on the sleeves for each set are normally brown for earth, yellow for main beam, green for dipped beam and red for sidelights.

ken

I've had a similar problem on the van (over the last few months)
Noticing a burning smell, I checked the switch to find it quite hot From then on I kept my night-time journeys to a minimum, and the vent flap open for some cooling! (secretly thinking the next nocturnal excursion could be our last)
I had thought that I'd no full beam, but checking the lights recently I found I did have full beam but no dipped (they're angled quite low) When we took the switch apart to give it its regular 40-year clean up, we discovered just how much damage that 'burning smell' had caused - one of the copper contacts was blue with corrosion; the other was so far out of position due to there being nothing for it to rest on, that it wouldn't make a circuit (hence no lamps) - lots of it had burned away, although it was arcing (slightly), hence the whiff of warm plastic

I have a replacement switch to fit now, and a few other electrickery bits, so hopefully all will be well for the upcoming MOT and the winter 2CV season

At least the headlamp switch gives you something to warm your hands on at this time of year

Given the age of any A series when anything electrical stops working starts smelling etc the first check should be of the hardware, check the wires for condition chaffed broken? get rid of the steel loom clip on the air filter leg, connectors all clean un corroded and female terminals still got tension? Dirty oily mess is not good for the electrics and no the oil does not keep water out. Fuses blown?( and whats the reason if they have).
Then id think about upgrading stuff that is a known problem,run new earth for the indicators fuel tank etc, Bin the side repeaters if you can, simplify the wiring and run decent earth if you cant. Disable the dim dip if the remnants are still there, the jumper is a stop gap till you fit fused and relay supply for the main headlights. Fit/move relays away from the splash zone down at the bulkhead seam to as high on the bulkhead as the wiring will allow.
Clean the contacts in the big switches - ignition, headlight and indicator.

The later looms were a bit of a mess from the factory and unless you dogmatically stick to the original spec because you have a factory fresh show specimen then changing a few things so it wont let you down on a dark rainy night is only sensible.
Sean

Not having worked on many 2CVs I can't comment on whether it's unique, Ken. But the lighting loom on my car is exactly as it left Mangualde, and on my car both headlamps share a common dipped beam feed which then passes to the single inline bullet connector and somewhere after that (I haven't teased the rest of the loom apart as I've not needed to) it clearly splits into the two separate lamp feeds.

What more can I say? I had the same fault as originally described in this thread and that's where I found the fault.