How to wire 12v switch?

[BTR22]

Just bought some 12v rocker switches. They have three spade connections on the back with no markings. How do I wire these? I was expecting just two connections one for +and one for -.

[CarlLaFong]

Are they on/off or on/off/on? Also, do not connect + to one and - to the other on any switch. The switch is an interrupter and should be spliced, in most cases, into the positive lead

[dh]

An on on switch will have two positions, an up and a down position. An on off on will have an up, center, and down positon.

With either switch the center terminal should be the + terminal and the switch will flip current between the two remaining terminals with the center position on the on off on powering neither terminal.

With an on on wire the device to one of the remaining terminals and leave the third terminal empty. This will act as an on off switch.

With an on off on the two remaining terminals can be jumped together and wired to the device so the center position is off and BOTH the up AND down positions will turn on the device on.

[Dale M.]

IF its a illuminated switch (lighted when on) one of the terminals will be a ground....

A two terminal switch is called a Single Pole Single Throw (SPST).

A three terminal switch is usually refered to as a Single Pole Double Throw (SPDT) if its not a illuminated version... Generally the center terminal is the "common" terminal and either of the two 'end' terminals will be either "on" or "off" depending on which way switch lever (or rocker) is "thrown"...

Test switch with a mock up circuit to understand "function" to understand the mechanics of it before your proceed and find out switch may no perform as you expect and find out it does not "work" in your application...

This link may be of help....

http://www.kpsec.freeuk.com/components/switch.htm

Dale

[dh]

Good point about the illuminated switch. However, I have yet to come accross one that wasn't marked on the body as to what went to what terminal. SPDT and DPDT switches usually lack the markings.

[Dale M.]

Good point about the illuminated switch. However, I have yet to come accross one that wasn't marked on the body as to what went to what terminal. SPDT and DPDT switches usually lack the markings.

Yes, you know this and so do I, but some others may not quite as observant or knowledgeable...

Dale

[dh]

Wasn't trying to argue or pick a fight Dale, just explaining that I based my reply on the stated fact in the OP that the switch had no markings on it.

[BTR22]

Test switch with a mock up circuit to understand "function" to understand the mechanics of it before your proceed and find out switch may no perform as you expect and find out it does not "work" in your application...


Thanks, this quote from the link explained it perfectly:

"This switch can be on in both positions, switching on a separate device in each case. It is often called a changeover switch. For example, a SPDT switch can be used to switch on a red lamp in one position and a green lamp in the other position.

A SPDT toggle switch may be used as a simple on-off switch by connecting to COM and one of the A or B terminals shown in the diagram. A and B are interchangeable so switches are usually not labelled."

I will Use the center as the COM and attach the exiting wire to one of the other connections. I will probably cover up the unused connection with spade connector and tape it up. Does this sound correct?

[angib]

Just to throw in my twopennyworth - it's good to see you bought 12v switches, as many people think 110v switches (or, worse still, 240v switches in Yurp) will do - after all they have a bigger number, so they must be better, right?

Domestic voltage switches are designed to be good insulators and it doesn't matter much if they have a high resistance.

In contrast 12v switches are designed for low resistance since stopping 12v switch arcing isn't a problem! This reduces the voltage drop across the switch so gives you more voltage (and more light) at the lamp.

[Dale M.]

Wasn't trying to argue or pick a fight Dale, just explaining that I based my reply on the stated fact in the OP that the switch had no markings on it.

Oops... Did mean to sound snippy or rude.... Its just that for the uninformed, there is a lot of myth and mystery to "electricity" and items associated with it.....

Dale

[dh]

The quoted link is refering to an on-on SPDT switch. If you have an on-off-on SPDT switch, the rules of the game change. There are a few ''tricks'' you can do with these switches besides the simple circuit described in the quoted link, but thats a whole nother thread. I insulate the open terminal like the used termials, which to me means leaving them exposed about 97% of the time.

"This switch can be on in both positions, switching on a separate device in each case. It is often called a changeover switch. For example, a SPDT switch can be used to switch on a red lamp in one position and a green lamp in the other position.

A SPDT toggle switch may be used as a simple on-off switch by connecting to COM and one of the A or B terminals shown in the diagram. A and B are interchangeable so switches are usually not labelled."

I will probably cover up the unused connection with spade connector and tape it up. Does this sound correct?

[Lit'l Shinee]

I have added a fan to the back of the trailer fridge to help move out the hot air, thus making it more efficient.

I also bought a lighted on/off switch so I can turn the fan off when I want to. At present there is a temp sensor on the coil that turns the fan on but sometimes it works too well and the fridge gets too cold and freezes stuff. I want to be able to turn the fan completely off when not needed.

The switch has 3 terminals on the back that are unmarked. I have read this whole thread but didn't see a description that related to a plain rocker switch that just does on/off and has the light in it. Two of the tabs on the back are silver and one is brass colored. Can anyone tell me which wire goes to what tab?

Thanks for any help,
Shinee

[DJT]

Usually the two silver will be your switched leads (i.e. in/out for your circuit) and the brassy one will be a ground for the light.

[Lit'l Shinee]

DJT thanks for the reply. I may be a little dense here so please excuse my ignorance. I assume by in/out you mean power and ground? If so would I have 2 wires that go to ground? One tying the switch and fan together and the other from the brass colored tab?

Does it matter which one of the 2 silver tabs is power and which is ground?

thanks,
Shinee

[Dale M.]

Does switch look like this?



Typically the left most connection (sort of brass color) would be ground (for internal lamp), the right terminal (silver) would be the "supply" (to battery/fuse) the center terminal (also silver) will be "output" to fan... Also is there any "numbers" on switch body designating terminals?

(note in example below the "pictures" are reversed to example above - terminal positions)



This diagram may also shed some light..... Note switch internal wiring diagram in upper right of design sheet ( yes I know the switch is designed for AC and we are working with DC but "concepts" are the same).......

By above design if you wanted switch to be "lighted" all the time (night light) wire the supply to terminal 2 and output to terminal 1..

If you want switch illumined only when "on" wire supply to terminal 1 and output to terminal two....


Dale