Why Won't My Blade Run When I Flick the Switch for My John Deere Front Mower?

Interlock System

• The Power Takeoff, or PTO, is the driveshaft that controls the blade. To prevent serious injury, John Deere front-end mowers have a safety interlock system that will prevent blade engagement or power to the engine. You must be fully seated before starting the engine; adjust it so that the seat springs down slightly when you are on it. When the engine is started, the choke should be turned off. Otherwise, the engine can get flooded with fuel and shut off, preventing PTO engagement.

Brake Systems

• John Deere front mowers have a master brake and parking brake to keep mowers stabilized at no higher than a 17-degree slope. If the parking brake is not engaged, the blade engagement knob or switch will not activate. The master brake control, which locks all wheels, must be disengaged to operate the PTO. You must recycle the PTO switch after releasing the master brake for the blade to become operable again.

Engine Overheat

• If the engine becomes overheated, PTO switch will not work. Turn the mower off and park it in the shade and allow it to cool off. Check the air intake screen to see if it’s plugged. Do not operate the front mower too long at idle or slow speeds, because it won’t produce enough cool air to keep the temperatures down.

Oil and Coolant Condition

• Engine oil levels can also affect the engine’s temperature. The low oil indicator light will stay on after starting the engine if levels are too low and the PTO won’t engage. Too much oil in the engine can backflow into the combustion chamber and ignite, raising the engine’s temperature. If the engine coolant light comes on, that indicates the coolant temperatures are too high. This also means that the engine temperature is too high for blade operation.