Hello, I have an older 80s model Magic Chef furnace - G83-75D-5. The furnace worked fine all last winter. I put in a new air filter in prep of winterizing and now the unit will not come on. The paperwork says to be sure the door is replaced correctly due to the safety interlock switch... I have taken the door off and put it back on serveral times with no luck. Any suggestions?

Thanks so much.