Blower fan/air con problem.
 

I have what is an infuriating problem on my 2001 E53 3.0D so would welcome some advice before I dive in and start pulling/changing things.

My heater blower/air con works perfectly aside from the fact that the blower fan seems to cut in and out when it feels like it irrespective of the temperature settings on the panel.

To give you some idea of what's going on, it's quite hot at the moment so when I get in and start the car, it'll work as normal and push out a decent amount of cold air at any selected fan speed but then when the inside of the car gets cold, it'll cut out. Then, when it gets hot inside the car, it'll cut back in. It's almost as if the range on the 'auto' setting is stupidly wide.

Oddly, it always seems to kick in shortly after I open the window (it's very hot at the moment!) but this may be a coincidence!

I have done tons of research and all roads seem to point to the FSR but I was wondering if anyone had experienced anything similar and had found a solution anywhere else.

Thanks for the information. I've tried forcing it to stay on by using different settings, fan speeds and even different temperatures but to no avail.

The plug is certainly on my list of things to check.

One interesting thing, I took out the air/pollen filter last night to see if it would make any difference to the air flow and it's been markedly better although it still cuts out eventually. Then comes back on when the internal temperature rises, etc.