motor driven water pump for cooling a still

Hi all New Bee here,

i have a temp sensor that will monitor the still temperature and will turn the pump on/off with pin 6 PWM driving a FET.

My problem, The PWM seems 25% on or fully on , nothing in between. would like so is slow then get faster, or fast then slow down , but my PWN

I my code below, it is a mix of my own and some else s i have modded
any tips?

test.doc (31.5 KB)

Is a PID really essential for maintaining temperature on something as large as a still?