Ok we're getting somewhere! There were 4 settings for each PWM mode under the advanced tab. Unfortunately none of them gave me control over the fan. But I decided to google what the difference was between the 4 settings (Manual PWM Control, Thermal Cruise, Fan Speed Cruise, Smart Fan III). I ended up at the speedfan homepage. Looks like the latest official release v4.42 doesn't support the chip I have (Winbond W83667HG-B) but the beta version does...Beta 4 allows fan control (verified) with W83667HG and W83667HG-B, restores full access to ATI southbridges, improves PWM control with IT8720F, adds full support for W83627DHG-P and is much faster at start. A lot of other fixes and improvements.
- Full Beta Info
In the 4.43b there are more options under each PWM mode. The only one I found to work is setting 'PWM 2 mode' to 'Manual'
Minimum and Maximum values are approx: 0% = 400rpm, 100% = 980rpm.
Thanks so much for your help, I feel like I'm finally getting somewhere! You mentioned that the CPU temp reading may not be accurate, is there something I can do to determine the actual temps?
When googling, I also found this
explaination for the difference between Manual, Thermal Cruise, Fan Speed Cruise & Smart Fan. As only Manual seems to work for me it's a bit irrelevant but it may be useful for someone else.