Everything is working normal at 300F. Oven gets to temperature, light turns off. Over time, the oven cycles normally to keep temperature, light goes on, light goes off. Then, the light goes on but it is also accompanied with a loud vibration sound from the lower unit as the unit struggles. If you slightly adjust the temperature, the light turns off and the noise goes away. The light turns on, the noise is rattling away again. I added a video file that has the rattling sound when the light comes on.
Any thoughts on the cause? It appears that temp is ok and ramps up and down as intended. I'm just worried that something is going crap out soon and I would like to be proactive and fix it before it dies.
Have you checked the burners. Either burning inside of the tube and making a rumble or you have a bearing going in the blower motor. It is possible to also be a switch or electrical connection that is intermittent. Like the door switch or the thermostat contacts. Not common! Check your burner first. It may have a crack.
Possibly a bad temp control potentiometer, I would try re-creating the noise by slightly turning the pot in the temp range where you have experienced this issue. If the unit is constantly run on the same temp it can create a bad funky spot, also look at rear of pot on temp controller.
Test the voltage from the Fenwall ignition control to the gas valve to be a full 24 volts. If the valve is chattering, that means the armature in the valve is not opening fully. Either the voltage isn't correct or something internally of the valve is preventing the armature from full travel.