I am rewiring my '54 f100 using an ez wiring kit. It is pretty straightforward. When I came to wiring my dash I decided to pull the random switches that the previous owner had put in the dash and opted to make a panel controlling lights, starter and wiper with toggle switches.

At the autozone I found a toggle that was really cheap looking. At the hardware store I found toggles that are of higher quality. When I mentioned my plan on the 48-60 forum one of the guys asserted that I had to use 12v dc switches. When I asked a local vendor (not autozone or radio shack) he said it didn't matter as long as the switch was rated high enough for the application. In other words, I could use the hardware store switches rated for ac motors (20 amp). The guy at the hardware store said "no way."

So, here are two opinions on the matter:

1). You MUST use the dc rated toggle switches in your automotive application.

2). You can use the ac toggle switches in your automotive application.

Is there a definative answer here? I'm really lost and can use the help. Thanks.

electronically challenged, himmelberg

 

As far as I know, and I have a degree in Electronics Engineering, you want a switch that is rated for AT LEAST the voltage and amperage of the application that you are using it for, any less and the possibility exist that the switch will burn up.

In other words, if you need a 12v switch with 5 amp rating, you can use a 50 volt switch with a 10 amp rating and so on. It's not the switch that you are worried about here, its the fuse, you definitely want the fuse to go before the switch. Don't be using AC fuses!

There are manufacturers who will list their switches with a rating of 20(5) @ 120VDC, then it will have a 5 AMP DC rating @ 120 VDC and a 20AMP AC rating. This would indicate that the switches can be used in either application. You shouldn't have a problem as long as you avoid the gawdy looking switches in your truck, my recommendation is to exceed the rating, and you are fine with AC or DC switches.

Final Answer - #2

 

yup, what 99 expy said above. as long as the switch is rated for a higher amp/volt than what you are going to put through it, you will have no problem. buy good once and never have a problem, or buy cheap and replace every other day.

 

And because the guys you talk to at those places gave you such bogus info. (I agree and have an Electronics degree from Purdue) I would not buy from any of those places.

We used to have so much fun going to these places like Best Buy and having the salesmen spew garbage about a car stereo. I especially loved the ones that would claim that 50 watt speakers put out 50 watts. Usually we'd just stand there and laugh at the guy, while he stood there not understanding. On the speakers, I'd always act real interested and then ask them to show me the manual where it says it puts out 50 watts. (for those that don't know, a 50 watt speaker handles up to 50 watts. It doesn't put out 50 watts, unless that's what you feed it.) Sometimes we really confuse them and ask them if we could feed 2 speakers off of one output. Sometimes they'd blow smoke and other times they'd try and look it up, but none every knew.

 

First off let me say that switches are rated mostly on their ability to extinguish an arc. If a switch is rated at 250V it means that it has the ability to break an arc up to 250V.

Switches are also rated in Amps so you need a switch that can break an arc for the amount of voltage you are using and to carry the amount of Amps that you are consuming.

Also it is hardier to break a DC arc than AC so as a good rule of thumb you need a switch rated two times the Voltage in DC or you need to put a capacitor around it.

Most switches are marked in booth AC and DC Voltages along with their current carrying capacity.

 

Subford is correct. Do not quickly dismiss the difference between a DC rated switch and a AC rated switch.

We have talked about this before, and I am in the middle of building a EV, so I have been doing some research and playing with DC circuits. This is the conclusion that I have come to so far; With only 12 volts, you can probably get away with using AC rated switches, just watching out for the amperage rating like the others said.

Of course there are high quality and low quality switches, but you can be guarenteed the DC rated switch will be more expensive and higher quality. The reason is as subford mentioned. When you are closing the contacts in the circuit, there really is no difference. It's when you turn the switch off or open the switch, that the difference comes into play. DC current will have a tendency to jump the contacts and want to keep flowing. A DC switch will open the contacts farther apart and may have some additional spark arresting designed into it. But I have found the general consensus is this only becomes a real problem with dc voltages 24 volts or higher(give or take). 12 volts is such a low potiental, arcing is not that great a problem.

This is also true with fuses. Some are rated DC, and others AC only. You will find DC fuses may have a sand like substance in them, or a spring, so when the element melts, the spring will pull the element in two and make a larger gap, and or the sand will help extinguish the arc when the element melts in two.

 

Thank you all for the information provided-- it is most helpful.

appreciatively, himmelberg