My 2001 Volvo S40 as an intermittent problem with the heating & cooling. The blower sometimes shuts off and then starts again at high speed.
Another problem that I have noticed is that the blower continues to blow warmair when the warmest to coolest temperature is turned to on the temp' dial.
Also continues to blow cool air when the opposite is done with the temp' dial, (cold to warm is switched).
These are all intermittent problems but none the less are annoying.

The Blower Fan Motor & Resistor have both been replacedand the problem is still there.
Also, the coolant has been flushed and replaced.

Please, can anyone advise on what the root cause is?