My 2016 Monte has developed a fault where the fan only works on No4. I'm thinking this is a resistor issue. Any ideas chaps , and before I call dealer tomorrow is it covered under 3 year warranty?

If it is under 3 years old then it has to be covered under warranty. After all it can hardly be put down to misuse so they can't argue otherwise.

Yup - my 2015 car had it replaced under warranty about a year ago. No hassle.