Good day to all. I am looking for some info on the ported vacuum switches. What I need to know is the function of each one. A DETAILED vacuum diagram might help, but not been able to find one yet. Any help would be appreciated. 1979 F-250 351M C-6

Thanks for your time, Gord

 

They don't have a specific function in the sense that I think you mean. How they work in circuit depends on how the circuit is set up. Another words, they are basically modular parts.

That said:
A 2-port PVS is simply a toggle switch. As soon as the coolant gets to a high enough temperature it switches on and allows vacuum to be drawn through the switch body. The inverse is true too, it keeps a circuit turned off as long as the temperature is too cold. It's usually used to control an EGR circuit (but not always).

A 3-port PVS is basically two toggles controlling one circuit. That is, when the engine is cold, the top port ('1') is connected to the middle port ('D'). When the coolant gets hot enough it switches over so that the bottom port ('2') is connected to the middle port ('D'). The commonest use to is an cold-start or overheat switch. With the overheat switch, the top port is connected to ported vacuum, the middle to the distributor vacuum advance, and the bottom port to manifold vac. When the engine gets too hot, the switch flips to manifold vacuum and you get more advance so the water pump and fan move faster and the engine cools down. You could use it to replace a 2-port toggle too. Cap the top port and hook the bottom port to a vacuum source and the middle to whatever it is your controlling and the circuit will stay closed until the engine reaches the right temperature.

The 4-port PVS is essentially two toggles ganged to the same temperature. The top two ports are connected together when the engine is below the switch temperature. When you reach the activation temperature, the top two ports are disconnected from each other and the bottom two ports are connected together.

The switches are different colors for different switches:
Green: switches over when above 70° (F° not C°)
Pink or 'natural' (?): 90°F
Black: 100°F
Blue or 'dichromatic' or 'plain': 133°F
Yellow or gray: 155°F
Red: 245°F

The colors apply regardless of number of ports on the switch. NB: the switches aren't exactly calibrated, and there's a temperature range around the indicated temperature where the switch will be halfway between the two states.

If you have the right vacuum diagram, then you have as detailed a diagram as you're going to get.

ash
['Hope that helps.']

 

Thank you very much. The detail was grand!!!

Have a great day and continue to share your knowledge.

Gord gslk1214