Yeah how is it staying at 145° if you have a thermostat?
The fan should be wired to a thermostatic switch at the very least, that way you’d have a a basic on/off at certain temperatures so you wouldn’t have to worry about manual control with a regular toggle switch.
This is a relay set up for a single 30 amp fan, not sure exactly what you have or what kind of amperage it pulls but this would be a super basic way to control the fan and pull the power so it’s not coming through the bulkhead connector.
Summit Racing SUM-890115 Summit Racing™ Electric Fan Thermostat Kits | Summit Racing
There’s other similar set ups with higher amp relays and different temperature switches are available for various on/off temperatures.
I use a Dakota Digital fan controller for my dual speed, dual electric fans but that’s a more complicated relay set up. The controller does have a lot of nice functions though, you can program and change the on/off temps for both fans and the high/low speed, change the run time after shut down etc…
Dakota Digital PAC-2800BT Dakota Digital Electronic Fan Controllers with Bluetooth | Summit Racing