C3 preheating lamp fault

I drive a C3 diesel too, and I remember something similar last winter. The preheating system relies on the preheating control unit. If the preheating lamp stays on, it often indicates a fault within that system. Is the smoke black, white or blue-ish?

The smoke is black, which I read means it's probably burning too much fuel. Did yours do that? If it was the preheating unit, was it a difficult fix?

Yes, the black smoke definitely points towards over-fuelling, which a malfunctioning preheating system can indeed trigger. Some mechanically inclined individuals might attempt a DIY fix, but diagnosing electrical faults can be tricky. Given the potential for further complications, and the link to over-fuelling, I'd suggest taking it to a reputable workshop. They can pinpoint the exact cause and ensure the repair is carried out correctly.

Okay, you're right, better safe than sorry! Took it to the shop, and you were spot on – turned out to be a dodgy connection to the preheating control unit. 95€ later, it's fixed and running like a dream! Thanks a million for your help!