Problems with Flowmaster Thermoswitch on Attic Fan

[whitedavidp]

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

[FatimaandAhmed]

Hi!

It sounds like you’re having a tough time with your attic fan thermostat. It’s really frustrating when the temperature control isn’t accurate, especially when you’ve set it to a specific temperature but the fan seems to act up regardless.

Bi-metal spring thermostats like the one you have can indeed wear out or become miscalibrated over time. If the fan changes state with just a slight adjustment, it could be a sign that the internal mechanism is failing or that the thermostat isn’t responding correctly anymore.

If you’re considering alternatives, you might look into digital thermostats, which tend to offer more precise control compared to the older mechanical models. They usually have better accuracy and might help solve the issue you’re facing. Also, checking in with a local HVAC professional could provide you with some tailored advice on replacing or upgrading the thermostat to something more reliable.

Switching to a new or different type of thermostat could help get your attic fan working as it should and save you from the hassle of constant adjustments.