Hello and thanks for any help you can offer...

Years ago we installed an attic fan and it came with a Master Flow 915379 thermostatic switch. Basically my problem is that this is just not accurate. Even when set to 85 degrees, this morning at 7am the fan was running. A digital thermometer in the attic showed 68 degrees. I note that sometimes just moving the setting on this switch the very slightest amount - sometimes just touching the knob with a screwdriver and not even turning - the fan's state will change.

I have never been impressed with these units and I think I have replaced one already. Do these just wear out? Are there reasonably priced alternatives? Maybe something digital and not just a bi-metal spring? Is there some other bi-metal spring based unit that is superior? This is just stupid.

Thanks