Its an simple Economizer setup, setpoint controlled by outside air temp. Below the setpoint the outside air kicks in and above the air intake turned...
That is why I carried a Wiggy as a real electrician, it puts a load on the circuit. With a digital you will never know what your reading, unless you...
It should have a glass bowl filter with a petcock in the bottom. Aside from a linkage sticking IF the diesel engine gets a shot of oil from a engine...
If not a mechanical person and don’t know about keeping good gas your equipment by all means get a good battery operated one. I find its a challenge...