Prior to effective engine computers,
engine vacuumwas used for many functions in an automobile. Vacuum switches were employed to regulate this flow, and were commonly controlled by temperature, solenoids, mechanically, or directly. They operated vacuum motors, other vacuum switches and other devices.
The engine in a common automobile produces almost 20 inches (51 cm) of vacuum, and this pressure differential may be harnessed for many uses. Engine vacuum is also the best direct source of information on the engine's load. Most delay valves have a one-way function, where there is either no restriction or no movement in one direction.
There are several common types of vacuum switches.
A valve that only allows the vacuum signal to move in one direction. Often used with vacuum reservoirs.
vacuum delay valveis a valve with a small orifice, which delays a vacuum signal. These are commonly used in automobiles to alter the behavior of a vacuum signal. Delay valves are usually color-coded to their function.
Coolant temperature override
Also referred to as a Temperature Vacuum Switch (TVS) or Thermal Vacuum Valve (TVV). The CTO switch measures coolant temperature, usually from a passage in the
intake manifold. It was commonly used starting in the 1960s for switching the vacuum advance from ported vacuumto manifold vacuumat high engine temperatures to promote cooler idling. As emissions controls expanded, it gained many other uses.
They commonly have between two and five vacuum ports.
Thermostatically-controlled air cleaner system
The factory air cleaner on
carburetored vehicles has a switch controlled by a bi-metallic stripthat ultimately selects cool or preheated air. This valve is usually open on one side to the air space within the air filter, and is both temperature controlled, and bleed style. Its function is to keep the air going in to the carburetor above a certain temperature to prevent icing.
Non-Linear vacuum regulator
A NLVR regulates vacuum signal so it is between two vacuum source levels. As one signal increases the other regulator valve switches to another vacuum source.
A bleed valve controls a metered orifice that adjusts to allow air into the line to weaken a vacuum signal. They are commonly controlled by coolant temperature or under hood air temperature, but may be part of the
A vacuum booster uses one vacuum signal, usually ported, to control another signal, usually manifold, that is stronger. It may also use a
Positive crankcase ventilation valve
The Positive Crankcase Ventilation (PCV) is a one-way valve that ensures continual refreshment of the air inside the engine's crankcase.
Vacuum electrical switch
A vacuum switch that turns an electrical connection on or off. Used for early electronic control modules to determine engine load or function.
solenoidthat switches a vacuum signal on or off.
Manual vacuum switch
Operator controlled switches were often used to control vacuum powered devices before the advent of robust automotive electrical systems or reliable mechanical linkages. They consisted of a variety of shapes, sizes, and configurations much like electrical switches.
They are commonly found as window and HVAC controls.
The term "vacuum switch" can also refer to a specialized type of electrical switch in which the contacts are enclosed in a vacuum envelope. This allows the switching of very high voltages with a compact switch, while preventing arcing across the contacts.
List of automotive vacuum devices
Automobile accessory power
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Look at other dictionaries:
vacuum switch — vakuuminis jungiklis statusas T sritis automatika atitikmenys: angl. vacuum switch vok. Vakuumschalter, m rus. вакуумный выключатель, m pranc. interrupteur à vide, m … Automatikos terminų žodynas
vacuum switch — See thermal vacuum switch … Dictionary of automotive terms
ported vacuum switch — (PVS) a temperature actuated switch that changes vacuum connections when the coolant temperature changes (originally used to switch spark port vacuum; now used for any vacuum switching function that requires coolant temperature sensing) … Dictionary of automotive terms
choke thermal vacuum switch — (CTVS) a switch used on some GM vehicle to deny vacuum to either the front or the auxiliary choke vacuum breaks. Its purpose is to slow the opening of the choke and to provide better driveability when the engine is cold … Dictionary of automotive terms
oil thermal vacuum switch — (OTVS) a switch used by some GM vehicle to shut off vacuum to the early evaporation (EFE) valve when oil temperature reaches 150° F … Dictionary of automotive terms
thermal vacuum switch — (TVS)  measures either air/fuel temperature, underhood temperature, or coolant temperature, or a combination of any two to regulate the EGR valve accordingly.  A temperature sensitive switch that shifts the source of the advance from ported … Dictionary of automotive terms
temperature vacuum switch — (TVS) controls vacuum to the EGR valve and/or canister purge valve based on coolant or intake air temperature. Canister purge and EGR do not typically operate when the engine is cold … Dictionary of automotive terms
thermostatic vacuum switch — A temperature sensitive switch which allows spark advance when engine idles for long periods … Dictionary of automotive terms
switch — A device that opens and closes an electric circuit. See actuating switch ambient temperature switch authority Limit Switch battery master switch dimmer switch dipper switch door pillar switch fuel cut off switch fuel pump shut off switch … Dictionary of automotive terms
Vacuum arc — A vacuum arc can arise when the surfaces of metal electrodes in contact with a good vacuum begin to emit electrons either through heating (thermionic emission) or via an electric field that is sufficient to cause field emission. Once initiated, a … Wikipedia