When a home inspector looks at a furnace, he or she is trying to determine the general condition of it, age etc. One thing I see, frequently, is the door or front panel interlock taped on. When an inspector sees that, there is little choice but to suggest that the appliance be looked at by an HVAC professional. The door interlock is a safety device, designed for the purpose of keeping someone from accidentally being injured by fiddling around inside the unit when it is running. This could range from a burn to being caught on a spinning electric motor. I suppose that the interlock is taped on because the person had a problem with the furnace not operating and, for whatever reason, they suspected the problem was the door interlock. Obviously, if the switch is not closed, then the furnace does not do run. Regardless, I think it curious that I find so many like this. I know several other inspectors in this community find the same thing. The photo below shows the suspect tape in all its glory.

Thanks for looking.

Steven L. Smith

Bellingham WA home inspector

www.kingofthehouse.com