I have an Ultra SX 80. It seems like everything is working except the main blower fan. It makes a humming noise and does not turn on even when the thermostat is set to on. Any thoughts? Board or motor maybe?


If the furnace is going through its processes and then after lit, the fan doesn't come on, and the unit shuts down again it would likely be the blower which if changed should change the capacitor on the blower too. That's really the best I can offer you from here.

Updated on January 8, 2018

Original Article:

Troubleshooting Common Furnace Problems With an HVAC Expert
By Dan Robbins