Topic-icon Reading "Switches" In Components

1 year 2 months ago - 1 year 2 months ago #777 by Mark
When checking for grounds through a component that shows switch type contacts enclosed in a circle, using a meter in  resistance mode will not read correctly.
The electrical theory behind how these work is beyond me, but I suspect we're looking at something like a silicon controlled rectifier that uses a "gate" to allow current flow.
To correctly check for grounds through these devices, the meter must be selected to  diode  mode and the test leads must be biased right. You will be reading the "voltage drop" across the diode. Normally this is about .5-.6 volts. If you see this drop, the "switch" can be considered to be "on".
The Fault Isolation Manual states "check for ground" when referencing these devices. It doesn't state exactly "how" that ground reading needs to be taken.
Last edit: 1 year 2 months ago by Mark.

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