Where is the reset button on my janitrol furnace model gmp075-3

There is not one on that unit. There is a roll out switch but it is not manually resettable. Also a door switch. Here is a site you can check out and find your parts. http://www.searspartsdirect.com/partsdirect/part-model/Janitrol-Parts/Furnace-Parts/Model-GMP0753/1771/0912130?searchedModel=gmp075-3&blt=05

Turn the power to the furnace off and then back on--- That will reset the conrol board but not any manual reset limits.