Coolant Temperature

Various switches are used to signal temperature changes to the MCU. Vehicles with 4 cylinder engines use an electric coolant switch mounted on a Ported Vacuum Switch (PVS). On 6 cylinder engines, a PVS sends vacuum to an electrical switch (mounted with 3 others) which is open when vacuum is applied. On V8 engines, 2 switches are mounted with sensors in a coolant passage. One switch is open when the engine is warm; the other is open both when the engine is cold and when it has overheated.