Peugeot Boxer 2.5 Diesel 1995 - Heater Fan question / problem.

My heater fan has suddenly stopped working on speeds 1,2 & 3 but works fine on full blast.

Anyone had the same problem? Is it a separate fuse or relay or is it some component inside the fan motor behind the glove box?
I am guessing it is a controller issue as I can’t find a separate fuse other than the 7.5A fuse behind the glove box. but I’ve heard that it may be a resister which is part of the fan?

Any auto electricians assistance would be greatly appreciated.

It’s a 1995 Peugeot Boxer. I’d like to be able to repair it myself to keep costs down as I am trying to sell the van. is this a big job?
(how come they always break when your trying to sell ‘em?)