# Vacuum switch

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{{One source|date=January 2026}}

Prior to effective [engine control unit](/source/engine_control_unit) computers, '''vacuum switches'''<ref>{{cite web |title=Electrical Vacuum Switch Replacement: Best Prices |url=https://www.yourmechanic.com/services/electrical-vacuum-switch-replacement |website=yourmechanic.com |access-date=28 January 2026}}</ref> were employed to regulate the flow of [engine vacuum](/source/engine_vacuum)s in [automobiles](/source/Automobile). 

For instance, a dual port vacuum switch located in a port on the [intake manifold](/source/intake_manifold) would monitor the [coolant](/source/coolant) temperature in the coolant crossover. It received vacuum (port E on the switch) from the [carburetor](/source/carburetor). The vacuum flowed through the switch to a vacuum [solenoid](/source/solenoid) such as a heat riser used to restrict exhaust, allowing the engine to heat up faster. When the coolant heated to operating temperature, the vacuum switch closed off the port (port S), turning off the vacuum to the heat riser. The result clears the exhaust restriction. The switch monitored the temperature, and performed its designed function under optimal conditions.

==See also==
* [Automobile accessory power](/source/Automobile_accessory_power)
* [Manifold vacuum](/source/Manifold_vacuum)

==References==
{{Reflist}}

{{Switches}}
Category:Switches

{{automotive-part-stub}}

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Adapted from the Wikipedia article [Vacuum switch](https://en.wikipedia.org/wiki/Vacuum_switch) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Vacuum_switch?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.