Onan Fault Code 33 [Cummins Generator Overheat]

A Onan generator may report a code 33, overheat.

You may need to replace:

  • sensor
  • radiator
  • fan belt
  • water pump
  • Coolant
  • Oil


Check the coolant and oil levels.

Owners report this issue happens after 1000 hours.

Note that it will shutdown itself if it gets too hot.


Fault code 33 status led will blink 3 times, pause, then 3more.

Here is a video of how one person fixed overheating: