Intertherm making weird noise

[JBeard]

I have a INTERTHERM furnace, the model number on the internals is E2EB-020HB. The furnace seems to work fine during the day but early in the day usually 2-3 a.m. it will start running then make a annoying humming noise followed by a knocking sound. It almost sounds like something is hitting the sides of the unit but when I open the door of the unit up I see nothing. Any thoughts on how to stop this would be greatly appreciated.

Thanks-Jason

[flcruising]

Do you have your thermostat set very low at night when it comes on at 2-3am? Once the home/unit starts heating up is when the noise subsides?

Turn the fan to ON at the thermostat and see if the noise happens without the heat being activated. Of course, it sounds like you need to be up at 2-3am to check.

[JBeard]

I have the heat set at 68 degrees all day long, I never turn it down at night.