I have a 2006 Renault master DCI 100 2.5 liter diesel van and the heater blower only works on high speed. Here is how to fix it. With pictures.
All it takes about 20 minutes or so depending how handy you are. First you have to take the blower motor out. Remove the single screw holding it in place and twist it counter clock wise and it comes out.
Next, behind it you’ll see the heater blower resistor pack. (white plastic with a wire connector) Twist it a quarter turn clock wise and it falls out. To put it back, twist it the other way.
When it’s out look at it and you’ll see 3 coils in it, those are the resistor coils. Leave them alone. Look in the cage inside on the top and you’ll see a watch spring looking metal piece. That’s the one half of the heat resistor that has separated from the lower part of it.
Now look at the other side of the cage and you’ll see the lower part of it where it separated from.
You can see where the top springy metal separated from. Press down through the hole on the top on that metal and press it against the lower half. That’s how you have to solder it together.
Just like you see it on the photo solder the heater resistor together and you’ll have all of your heater blower speed working on your renault master. This is what you need for the job.
Good Luck Ya’ll