Coolant Level Sensor: Description and Operation

The coolant level switch is an assembly containing a reed switch and magnetic float. When the coolant level is normal, the float rests away from the reed switch, causing the switch to open. When the coolant level is low, the float rests near the reed switch and causes the switch to close.

The coolant level switch is mounted in the radiator surge tank. If the coolant level falls below a specific level, the contacts close, and a signal is sent to the PCM. The PCM will then send this signal to the IPC to illuminate the coolant level telltale lamp.