How to connect a 3 wire momentary switch

CAPTAIN FANTASTIC

CAPTAIN FANTASTIC

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I want to wire up a momentary switch to a relay. The relay is not a problem because I have the wiring diagram; but I am having problem with the momentary switch, it has 3 wire connections instead of two. The connections are marked as 1,2,3 and there is nothing else. When I connect the test meter between connections 1 and 2 and press the button, I have continuity; where do I connect 3 to?. The switch has an LED to indicate when on I presume. Also, the switch when is pressed, springs back. The aim is to press the switch to energise the relay, the switch springs back to its original position and the relay cuts out after 10 minutes. (It will be used to operate a heated rear window on a car; but it could have been used on a boat as well!!)
 
CAPTAIN FANTASTIC said:
I want to wire up a momentary switch to a relay. The relay is not a problem because I have the wiring diagram; but I am having problem with the momentary switch, it has 3 wire connections instead of two. The connections are marked as 1,2,3 and there is nothing else. When I connect the test meter between connections 1 and 2 and press the button, I have continuity; where do I connect 3 to?. The switch has an LED to indicate when on I presume. Also, the switch when is pressed, springs back. The aim is to press the switch to energise the relay, the switch springs back to its original position and the relay cuts out after 10 minutes. (It will be used to operate a heated rear window on a car; but it could have been used on a boat as well!!)
Click to expand...

Is there continuity between 1 and 3 or 2 and 3 when the button is not pressed??

If there is illumination then the other connection could be for a negative supply for the light.
 
1 & 2 should be in the live feed to the relay, and 3 sounds like it should be connected to the negative to make the light work on the switch. If you don't want the light to operate just ignore 3

What do you want the switch to do?

if it's a momentary switch it will make the circuit (and operate the relay) when it is pressed then break the circuit as soon as you take your finger off the switch. If you want the relay to stay closed then you don't need a momentary switch, you need an on off switch (SPST).

I've never heard of a momentary switch that operates for 10 mins. Is it a car switch that is designed that way?
 
DavidGrieves said:
1 & 2 should be in the live feed to the relay, and 3 sounds like it should be connected to the negative to make the light work on the switch. If you don't want the light to operate just ignore 3

What do you want the switch to do?

if it's a momentary switch it will make the circuit (and operate the relay) when it is pressed then break the circuit as soon as you take your finger off the switch. If you want the relay to stay closed then you don't need a momentary switch, you need an on off switch (SPST).

I've never heard of a momentary switch that operates for 10 mins. Is it a car switch that is designed that way?
Click to expand...

Thanks for the reply. I have a relay that is suitable to operate a rear heated window on a car, it switches off after 10 minutes; but I need a switch to operate the relay. The switch I have is a momentary rocker switch that springs back when pressed. So the aim is to press the switch to energise the relay and the relay will cut out after 10 minutes; same as the car heated rear window switch. I did not want to fit a switch that you flicks to "on" position and then having to flick it to "off" position again manually. I presume pins 1 and 2 are positive to relay and pin 3 negative to feed the LED?? Is my thinking correct?
 
CAPTAIN FANTASTIC said:
Thanks for the reply. I have a relay that is suitable to operate a rear heated window on a car, it switches off after 10 minutes; but I need a switch to operate the relay. The switch I have is a momentary rocker switch that springs back when pressed. So the aim is to press the switch to energise the relay and the relay will cut out after 10 minutes; same as the car heated rear window switch. I did not want to fit a switch that you flicks to "on" position and then having to flick it to "off" position again manually. I presume pins 1 and 2 are positive to relay and pin 3 negative to feed the LED?? Is my thinking correct?
Click to expand...

Yeah I think you've got it right.

From battery live (fuse box) to 1 then from 2 to your relay and 3 to the neg.

Interested to know what you are operating for 10 mins?
 
As said the third connection must be a return for internal light. You could ignore that connection and have no light. However ideally for you purpose the light should be on when the heater is on. That could be tricky. You need a 12v supply for testing. Connect negative to term 3 and pos to term one. Press the switch does the light glow. If it glows continuously then connect +ve to term 2 does the light glow on when the switch is pressed or continuously? Ok so those tests should sort having the light glow when the switch is pressed. To have it glow when the heater is on you will I think need to apply the 12v supply to that terminal where the light glows continually with power applied. Then take the negative term 3 through anpother cobntact on the relay to prove a negative when the relay is operated. good luck olewill
 
Connect 1 to +ve in and 2 to operate the relay, if you want to get posh you can fit another relay triggered by the supply to the rear window that connects no3 to earth, then the light will be on whilst the heated window is working.

If that makes sense?
 
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