AL62707 Switch Thermostart Fits John Deere: 3120,1020,1030,1120,1130,1630,One New Aftermarket Replacement Thermostart Switch Fits John Deere Tractors This Thermostart switch is a key component of the cold starting system on Fits John Deere tractors. It controls the intake manifold heater (Thermostart unit) that warms incoming air to aid diesel engine starting in cold weather conditions. The switch typically installs by screwing into a port on the engine block or intake manifold and connects via standard electrical