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# 3 terminal switch question

#1
10-17-07, 08:48 PM
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Join Date: Oct 2007
Posts: 2
3 terminal switch question

i have a 3 terminal switch like this i need to put in my car to connect a fog lamp

how do i know which one is ground? or does it really matter? Im new to this stuff

Thanx..

#2
10-18-07, 12:07 AM
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Join Date: Mar 2006
Location: USA
Posts: 33,125
Normally three connectors would indicate two functions. Does the fog lamp have a high and low beam? Except in some circuits such as horn the positive is switched so the ground would not be connected to the switch, only the positive. Did the switch come with the fog lamp? How many wires from the fog lamp?

#3
10-18-07, 06:21 AM
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Join Date: Sep 2002
Location: welland ontario
Posts: 5,667
First thing is none of them are ground.
The way you use that switch depends entirely on the switch. There are many combination that this switch could be.
It could be center off, up on item one, down on item two.
It could be up one on, down two on.
There s hould be a drawing on the side of the switch indicating a common terminal and the NC(normally closed) and an NO(normally open), or other combination of how the switch works.

#4
10-18-07, 07:21 AM
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Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
The only reason a switch like this needs a ground is if the switch is lighted.

If you cannot find a wiring digram on the switch then use a meter and ohm out the switch.

#5
10-18-07, 11:01 AM
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Join Date: Sep 2002
Location: welland ontario
Posts: 5,667
Never thought of the light. Good point about the ground for a lighted switch.

#6
10-18-07, 03:03 PM
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Join Date: Oct 2007
Posts: 2
well yea, sorry bout that, it is a lighted switch like this

let me give the scenario, the car is prewired, i found the 3 wires needed to connect to the switch. One for power (blue), one for ground (black), and one for the fog light itself (green)...just wanted to know which terminal is for what. It has no diagram on it

#7
10-18-07, 03:59 PM
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Join Date: Sep 2002
Location: welland ontario
Posts: 5,667
If it has no drawing then you need to reference the manufacturer literature. You need to be sure the light part is 12 volts. It could be 120 volts.

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