Was underneath my new to me 84 S65 Hijet replacing the fuel filter and I found a switch marked S and W. What does this switch do? Thank you in advance
It is the damper for the air feed. Winter brings air from the left frame rail, across the catalytic converter and to the air cleaner. The Summer position pulls from the right frame rail to the air cleaner. I think the manual damper disappeared with the upsizing from the 550-cc EB engines, to the 660-cc EF engines. With the EF engines having a vacuum controlled damper, which utilizes a thermostatic vacuum switch to control which direction the air comes from.
