If you have a spare heater output (or you use RRF3, which allows you to configure a fan pin as a heater output), you can connect the fan to it. Then use the M307 I parameter for that heater to invert the sense of operation, i.e. the PWM will increase as the temperature rises. Is that what you need?

Solution!, I had checked literally everything and replaced everything, turns out it was the wire, I set my multimeter to continuity mode and found that there was an internal break in my + wire connecting to the fan, looked intact and was the only other part I hadn't replaced, now that thats gone and a new wire is in place I am up and running with it, so it seems anyway! Thanks for the support guys!

@bearer I don't disagree, just caution that heat sinks need to have good contact to actually sink heat otherwise they can do more harm than good.

@deckingman I stand corrected!

@3mm If you want to try it out, I would be willing to give you a heatsink to do the proper thermal investigation. I have 2 more heatsinks, since they come in a 3 pack.

I presume you have connected the input of your integrator to the FAN- pin of the FAN0 connector. Did you also connect a pullup resistor between FAN- and +5V?

Thanks, I'll give it a go.