5W lighting circuit fault diagnosis help needed please!?

Hi everyone, watts up?!!

Several years ago my VX began to exhibit an intermittent fault in the 5w bulb circuit, (on the first click of the stalk), which meant that the running lights would not come on one day but were fine the next. It started with the rears only refusing to come on and then all bulbs including the dash lights on the 'first click' circuit. No voltage is reaching the bulb holders. Headlights work normally in low and main beam and brake light filaments also work in the dual filament bulbs we use in the U.K. (P21/5w combined).

The only clue I have is that it seemed to develop after driving through a deep puddle one morning and presumably splashing water where it normally wouldn't go but as for finding the origin I'd have to strip the engine bay down to even access the wiring and it's been sat for years and had plenty of time to dry out if that's the problem. All fuses look fine and swapping out the headlight relay does nothing and should do nothing. I can hear it click when it comes on but no clicks on the first click of the stalk for the 5w bulbs. Do these even have relays? I don't think so. Does anyone else know what may be the cause of such a fault and the best way to diagnose it? I've heard of bad ground connections but have no idea where one may be on this truck, even with a wiring diagram as it doesn't even mention the 5 watt circuit.

I'm stumped by a simple issue that shouldn't even be possible and any help would be greatly appreciated!


For what it's worth, my Smart ForTwo has also developed the exact same fault, sitting for years next to the VX! Maybe a squirrel has eaten the wiring?