Need help choosing a switch and wiring it.

i4Marc

i4Marc

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Oct 19, 2011
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I do some motorcycle racing. To keep the tires up to temp when on standby I use tire warmers. the switches are made of cheap plastic. They get stepped on and run over etc. and end up getting smashed. I repaired it once and it worked great but this time it cannot be fixed. I would like to replace the plastic switches with durable metal switches similar to the bottom image. The function of the switch is not ON/OFF. It is WARM/HOT. So it is on all the time but there is a high and low temp circuit. See images below. I stamped the inside of the case with a "w" for the warm side and an "h" for the hot side of the switch. Can someone please suggest a switch that will replicate the function of my current switch? What is the switch called and how should it be wired to get me the high and low temp circuits?






 
You can use a toggle like the one in your post but it would need to be a 3 position switch that would give you off/warm/hot but to know what switch you would need will require some more info. Is the unit 12v? Any idea how many amps it uses?
 
To get a switch, go to www.digikey.com. They have a huge selection including some very heavy-duty switches. For a heavy-duty switch, expect to pay $10-12; it's expensive, but it is worth it in the long run. The switch you need is called a SPST, single-pole-single-throw, also know as a simple on/off switch.

I will recommend a switch rated for at least 120VAC. A higher rating is fine.

I googled for motorcycle tire warmer. The first one I found was rated for 1500W. At 120V, that is 12.5 Amps. So, look for a switch rated for at least 13A.

Digikey will also have a selection of heavy-duty boxes you can mount the switch in, the sort of things that can be stepped on, run over, etc. and survive.

In the picture, I believe that the cord entering on the bottom is the line cord (the one that plugs into the power source). The top cord exitting is to the heater. The heater actually has two elements. The low setting only runs one element and the high setting runs both. The black wire is "just passing through;" inside the heater, it goes to both elements. The green wire is the other wire from the low element. It connects to the white wire from the source so that he low element is always-on. The top white wire is the other side of the hot element and it goes to the source white wire through the switch.
 
Here's a thought: Go to Home Depot and get a standard light switch; that'll cost less than $2. You can also get a standard wall box and plate to mount it for another buck. Physically, it will be larger, but that may be nice (less likely to be stepped on). That switch is rated for 250V @ 15A. Just be sure to get one with screw terminals (the push-in type require solid -- not stranded -- wire).

You can get outdoor-rated switches and boxes and hardware for not a whole-lot more; that would be a good idea in case of rain or a water splash or just to keep dirt out.
 
Gollnick,

Thanks for the info. Wouldn't a simple on/off switch cut the power in the "off" position? I need the switch to be warm/hot or "on/on". Or am I not understanding the circuit? I would prefer a smaller toggle switch similar to the one I posted as opposed to a wall type switch. Can smaller toggles handle the power? I would think they should. You saw the cheap plastic switch I posted. It's pretty light weight and it is designed for the circuit. Can you post a simple drawing of how I would convert the connections in the cheap plastic switch to the kind of terminals I would find on the kind of switch I want to convert to? I guess I would be looking for an "on/on" or "on/off/on" type of switch. So if you do post a diagram use those as examples.


Thanks, Marc
 
The tire warmer itself has two heating elements inside of it. One of the two is always on. The other is controlled by the high/low switch. If only the first element is on, then that is low power. If the second element is turned on, that is high-power. So, the switch only controls -- turns on and off -- the second element. The first element is always on.

Am I correct that the cable seen in your picture entering the switch box from the top, the cable that has a black, a white, and a green wire within it, is going to the actual tire heater? Am I correct that the cable seen entering the switch box from the bottom, the cable with a black and a white wire inside of it, is the line cord going to the power source?
 
Gollnick,

Ok, I understand the circuit better now that you explained it that way. You are correct. The B&W side goes to the plug. The black, white and green wires lead to the warmer.
 
Then all you need is a Single-pole-single-throw (SPST) switch.

I recommend at least 8 amps current rating and at least 120VAC voltage rating.

Digikey and Mouser Electronics probably have the biggest selections on-line. You could use a slide switch, a toggle switch, or a rocker switch nicely. Toggle switches usually mount in simple round holes; rocker and slide switches require rectangular holes so you'll need more than a simple drill.

As I noted, both Digikey and Mouser will have project boxes that you can mount the switch in. Since there is no third-prong safety ground here, please use a plastic box.

(Some may question the lack of a safety ground. But, these devices are usually powered from portable generators which aren't grounded anyway. So, just insulate everything well.)
 
Great. Thanks for all the info. When I get a switch selected maybe I'll ask you for "what-goes-where" directions.
 
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