The Vernet cooling fan thermocontact, with an M22x150 thread, activates the fan when the temperature reaches 82 °C and then shuts it off when it drops back to 77 °C at the thermocontact.
These temperatures are fixed and cannot be adjusted. The 5 °C difference between activation and deactivation—known as hysteresis—limits repeated on-and-off cycles when the temperature fluctuates around the activation temperature.
Each engine has an optimal operating temperature range defined by its manufacturer. The choice of thermocontact must meet the engine’s requirements and be consistent with the thermostat, the radiator, and the location of the contactor within the cooling system. An earlier fan activation is not always beneficial.
The temperatures of 82 °C at activation and 77 °C at deactivation correspond to the temperature at the thermocontact. They do not, by themselves, define the engine’s optimal temperature and should not be confused with the thermostat’s opening temperature, which regulates cooling fluid flow.
Use an adapter on the coolant hose with an M22x150 thread, matched to the hose’s inner diameter, or use an available location with the same thread on the cooling system. The sensor element of the thermocontact must be in contact with the cooling fluid. Check the available space, the connections, and the seal of the mounting.
Mounting with a relay: The thermocontact must be connected to the control circuit of a relay, not to the power circuit. It controls the relay coil, while the relay’s power contacts supply power to the fan. Do not power the fan motor directly through the thermocontact.
Use a relay, a protective fuse, and cables with a cross-sectional area suitable for the fan’s consumption, taking its starting current into account. Follow the wiring diagrams for the relay and the vehicle.
