Hello,

I have a Miller oil furnace Model MSBA-066ABFO-05 that fires up and then shuts down because the fan takes to long to turn on. When this happens the reset trips on the controlor. The fan comes on shortly after the limit trips. When the fan is running if I push the reset the burner fires and continues to run until temp is met.

Which switch is faulty?

They are small disc switches. Schmatic shows Aux switch... Temp limit switch & fan switch.

Regards, John

I would suspect the fan switch BUT the limit switch could also be out of range cutting off to soon causing the burner to stop. A quality temperature tester is of great help when working on this type of problem. Just to be sure you could just replace both but make sure they are the exact number/temp set parts.

I took the thermodisk switches to a heating supply store and he didn't have any in stock. He tested them with a ohm meter and lighter which I questioned. Yes it switches... but is it within range? He suspects a problem with the high voltage coil. I agree with you. The switch is out of range and needs replaced. I'll make a few more calls and try to locate one. Thanks

Sometimes Miller parts have to be ordered. I believe Nordyne now owns Miller.