I soon hope to buy a Simca, with "eclair" as one of the dashboard controls. Is this a reference to the lights?
Yes, it is indeed a short form of éclairage used on some Simca dashboards.
Here an Ariane 4 SL 1959 model dashboard:
and here is an excerpt from an add of the Vedette V8 1956 model:
The buttons labels are:
- CHAUF : Chauffage (heater) on the Vedette V8
- CLIMAT : Climatisation (air conditioning) on the Ariane 4
- START : Starter (choke)
- ECLAIR: Éclairage (lights)
- AVERT : Avertisseur (horn)
- ESS GL: Essuie glace (wiper)
- DEMAR : Démarreur (starter)