What this table is for
The Thermo Fan Duty Cycle table sets the duty the ECU sends to the thermofan output. On a fan with a PWM speed controller, less duty generally means a slower fan and more duty a faster one. You'd normally raise the duty as temperature rises, so the fan is quiet when it's cool and runs hard when the engine needs it. The table supports up to two axes, so you could add a second input alongside temperature if your setup calls for it.
When you need it
Only when the fan is speed-controlled. A simple relay-switched fan is either on or off, and a changing duty won't do anything useful for it.
What to check
- The table's axis really is the temperature you want to control, usually coolant.
- Duty climbs smoothly with temperature, with no sudden steps that make the fan surge.
- Top duty is reached before the engine gets close to its warning temperature.
- The output and frequency match your fan controller; see thermofan wiring.
Need this diagram? Ask us and we'll send it over with advice for your build.
