heater blower
 

hi all I have a 2004 d5 xc90 .
last june the heater blower stopped working after checking fuses ect it came down to the blower resistor module had packed up so I bought new one fitted it all working fine again until 3 days ago when I turned the fan on to demist the screen nothing again . all the little green lights come on one by one as you rotate the switch but no blow .
so I thought the cheap resistor I got from ebay must have packed up .
took blower unit out took the plug with the 2 wires for the motor out put 12v to them and the motor works as it should so checked the power feed to the resistor and that,s fine so I bought another new resistor which came today and I have just fitted it and connected the plugs back up but still nothing .
I have checked the blue wire with a volt meter [and the yellow] but regardless of switch position there is no voltage at either the blue or yellow wires in the 4 pin socket there is 12v at the red feed wire .
so can anyone give any idea on whet to check next please .
I,m considering that it may be the rotary switch output as ive checked the blue and yellow wires at the multipin connector that plugs into the rear of the switching panel but still no output there either
thanks for any help you may be able to give

Sounds like a job for Vida.
You can run a CCM calibration, view temperature sensor data and view button and dial inputs.
Viewing what is actually happening or what the system thinks is happening is often the best way to troubleshoot on our cars.

If you don't have or want Vida, perhaps someone local can plug you in?