Garage furnace not working

[hbar218]

I think the elbow right off the unit and the sidewall vent might be part of the need for the fan. Usually they vent out the roof through natural convection. Newer ones have a combustion blower to help get the exhaust gasses out.

 

[Audette13]

Eric that is an awesome set up.. That Hi limit (blocked vent switch) is there in case the unit starts back drafting, the vent becomes blocked or unit overheats due to fan failure. If if was that switch causing this particular issue he would have to be resetting it by hand(you can see in your 3rd picture, the button in the middle of the switch), Hi limit switches should be manual reset. If its changed to an Auto reset and the blower fan fails, that thing will cycle on and off on that switch and cook the unit.

I like the aux cooling fan installed though, beauty hahahah