My 70s model intertherm oil furace keeps kicking the reset button, I have replaced all the vital componants( pump,motor,nozzle,electrodes, fuel& lines & made sure the Cad cell was clean) the furnace fires up but will only run for 30sec. & kicks the reset. I checked the flu & it was rusted completely , I plan on putting new sheet metal to this flu , could this be the reason? Its in an old mobile home I use for Deer camp So Id like to get as much use as possible from the parts Ive installed, Thank you

Are you talking about the roll out switch that you are reseting?

Possibly,I'm resetting the red button to the right of the electrodes ontop side of a control box

If it is the roll out switch then yes the flue could have something to do with it. Model number of the furnace?

The mod# is MAC1265 , it's a 61000 BTU Intertherm oil furnace, in a 70' mobile home

You are probably getting exhaust gas recirculation into the combustion air. Those old MAC furnaces were notorious for that. The ONLY cure is to replace the furnace unless you get lucky & find a heat exchanger.

Ok thanks for your Help...