Fix? Window switch that works but does not light up?

On my 348 all 3 switch modules are electrically identical (different legends, and one has a different coloured terminal block) - but you could try swapping them around to see if the problem moves with the module.

Alternatively, just because removing the door cards is a faff, (and I was too much of a wuss to try and prise the switches from the front) , could you not just remove the passenger one, then put power to the "lighting up" terminals from another 12V source, say on fly leads from your "daily" 's battery?

However, I wouldn't be surprised if the fault isn't at the switch - but at the big connectors in the door jamb. Definitely, for me, "Job1" would be to open that connector and give it a good clean with electrical contact cleaner, then peal back the flexible rubber conduits and have a look for broken connectors.

(When I first got my 348, passenger window, interior light, mirrors (heat & move) , drivers door speaker, drivers end of door light and occasionally central locking didnt work - ALL were vastly improved by sorting the drivers door connector out and cleaning the passenger one)


EDIT: Actually, re-reading my post - I should have just put "My rule of thumb when working on the electrics of my 348 is to 100% establish that I have power to the "thing" , usually by swapping out with a duplicate, or checking connectors, long before I even consider looking for a replacement." If we say I had 10-15 electrical faults on mine when I got it - I bought ONE replacement switch - and even that I might have broken myself.

 

There's an LED inside the switch that is soldered in so it's not as easy as just replacing a bulb (see here: http://www.ferrarichat.com/forum/technical-q-sponsored-algar-ferrari/368608-how-fix-clean-348-maybe-others-window-switches.html ).

As already suggested, I'd try one of the switches from the drivers door in the passenger door just to check if that one then lights up.

If it doesn't light up then you have a wiring issue somewhere.
If it does light up then your LED has given up the ghost in your original passenger door switch.

If the LED has gone then you could try to source a replacement and solder it in, but TBH, as the switches are available new from Eurospares for @ $27, I'd just replace the switch.