Thanks for the help both of you, unfortunately it doesn't seem to work. I've both attempted to configure fancontrol and setting the values manually., I can see that the values of /dev/fan-{p6,p7}/pwm1 change but that doesn't make the actual fans spin any faster or slower. I've also tried swapping the fans between P6 and P7 and confirmed that both work, and the fan connected to P7 always spins at a constant speed (a little slower on battery power than when the PSU is connected) whereas the fan connected to P6 usually spins for about a second then stops.