Look for freezing on the evaporator coil if temperatures are above 20 degrees, which is when the fan is supposed to come on and prevent water from refreezing. If there is freezing, the fan cycling control switch could be broken.
Turn the power off to your walk-in freezer, and unplug it. Failure to do so can cause electrocution during troubleshooting.
Examine the wiring connections from the fan motors to the timer switch and motors. Look for any obvious damage like tears or arcing.
Disconnect the fan motor wiring using your screwdrivers. Set your multimeter to test for ohms resistance and place the probes on the fan motor terminals.
If you receive a zero reading with no activity, the fan motor could be shorted out.
Inspect the timing switches to ensure they are in the open position. When the thermostat reaches the set temperature, the switch should close and signal the fan to operate.
Check the thermostat for continuity as performed in Step 4. If the thermostat has short-circuited, it won’t be able to signal the fans to come on.