Thermo Plunger is an additional electric heating element that warms up the coolant that passed through the engine and then to the heater core that warms the passenger compartment .
The sole purpose of thermo plunger is not cold -starting. Its main function is to make the passenger compartment little warmer and de-froze the windshield during extreme cold weather conditions, During early mornings at some extreme cold countries, the engine will take little time to send the required heat to this defrozer and passenger heater, and that job is fulfilled by this thermo-plunger unit
Thermo plunger is used in Nissan Juke K9k diesel version, Qashqai k9k engine, R9m engine variant, Volkswagen Tdi variant in extreme cold countries like Europe and Russia.
When diesel engine is in idle condition, ie. before moving the vehicle , the engine will produce less amounts of heat. At such cold conditions, this thermo-plunger will play a major role.
Once your vehicle started moving and more heat is produced by the engine, the engine coolant will reach a sufficient temperature to operate heater and the thermo-plunger will switch off. Thermo-plunger will be present coolant circuit between heater outlet and engine inlet circuit and it will be operated by an electric relay.