How to Start an Onan Generator With Jumper Cables

by Kurt SchanamanUpdated July 21, 2017
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Items you will need

  • Eye protection goggles

  • Jumper cables

  • Other power source

Onan generators come in a variety of models and sizes, capable of providing power for recreational vehicles, power tools, and even homes. Many Onan generators with electronic ignitions can experience battery degradation if they aren't used for extended periods, especially when not used for long durations throughout cold winter months. Onan generators may be "jump started" with jumper cables in the same way automobiles can be started, but safety measures should be performed to prevent injury or fatality.

Put on your eye protection goggles before continuing with jump starting the Onan generator.

Park an operable vehicle near the location of your Onan generator, and as close to the battery service compartment door on the Onan generator as possible. Most Onan generators have the batteries concealed within such battery compartments to prevent moisture and corrosion.

Open the battery service compartment door to expose the battery. Onan generators come with two types of latches on these battery compartment doors. On select models, there is a lever that can be flipped up, but must then be twisted counter-clockwise to release the latching mechanism. On other Onan models, the levers can be pushed toward the left allowing the containment door to be opened. In the event your Onan generator is of a newer model that isn't described by this guideline, please consult your maintenance manual for how to expose the battery for your specific model.

Prop the battery compartment door open and allow at least 30 minutes for the battery compartment to become ventilated. Explosive gasses are produced by most batteries and they can fill the battery compartment which poses a serious hazard. Sparks produced when connecting jumper cables may ignite the gasses, so be sure this ventilation procedure is strictly followed.

Open the engine compartment of the operating vehicle and connect the black negative (-) clamp on one end of the jumper cable set to the negative (-) post of the vehicle battery. Connect the black negative (-) clamp on the other end of the jumper cable set to any bare (unpainted) metal of the Onan generator's frame.

Connect the red positive (+) clamp on one end of the jumper cable set to the positive (+) post of the vehicle battery, then connect the red positive (+) clamp on the other end of the jumper cable set to the positive (+) post of the Onan generator unit's battery.

Charge the Onan generator unit's battery for about five minutes by allowing the vehicle to run while the jumper cables are connected. Start the Onan generator once the battery has been given this time to charge to reasonable starting voltage.

Disconnect the jumper cables from both the vehicle and the generator immediately once the generator has been started. Prevent the red and black jumper cable clamps from touching one another while both jaws of the other end are still connected to a battery to prevent sparks and damage to the battery.


Never leave a running vehicle unattended while jump starting your Onan generator to prevent injury to children and bystanders. Negative jaws of jumper cables should only be connected to a metal surface of the equipment frame of the unit in which the battery is discharged rather than to the negative post of the battery itself. This is an adequate negative connection while protecting the battery from potential sparks, providing a second line of defense against accidental sparks and explosions of the battery. Do not smoke cigarettes, cigars or pipes around exposed batteries and prevent others from doing so.

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