Some HVAC Troubleshooting Tips... If you have a blown fuse or breaker, shut off the local disconnect. Replace the fuses and turn on the main or reset the breaker. Check for proper power before turning on the local disconnect. If it's present, most likely your issue isn't in the circuit between the switches. Use a megger or meter to check for ground faults or shorted loads. A visual is also good as well. I used the @supco_hvac IDVM 550 to troubleshoot this call. Looks like this one fuse may have