Positive vs Negative Switching

Are they any advantages/disadvantages when wring a switch for lights on the positive side or negative side of the light?

Examples:

POS ---> Light ---> switch ---> NEG

Vs

POS ---> switch ---> Light ---> NEG

Any input would be appreciated.

 

I found this on google..it's online so it's gotta be true
https://www.google.com/url?sa=t&sou...8b4I97W0yJiq66B8w&sig2=H92KEym4btutPmLHfaLwGQ
Tacomaworld.com one
https://www.google.com/url?sa=t&sou...tpxeVgiuxLcc-EOzw&sig2=5gTLa7VA5eUIxR7tgRTc-w

 

Thanks

 

No problem..That's why we're all here
(err most of us)

 

All of the OE lights and switches are negative switched and it will work just fine if you reuse the OE fog light wires for example for a set of aftermarket lights. If you are using the OE wiring you just have to be careful to order the correct switches if you swap out to aftermarket custom switches, just let the, know you need a negative switched switch. It will still work but the switch will not illuminate unless it is built for a net switch set up.

 

I had no idea that OE was negative switched. Thanks for the info!

 

A switch in DC (especially a single normally open switch) doesn't care whether it's in or out. Usually pinout on switches is for any LED indicators inside it. LEDs almost always have a resistor in front of them to step down the current going into the LED. A single position normally open switch doesn't care which side is power or ground in a DC circuit. To a switch it's either open or closed and nothing else.

 

Yeah, I understand that part. I was just wondering if there is a "best practices" or prefered method.

 

most older vehicles with a negative ground switch the positive side of the circuit because it's easy to connect the other side of the load to a metal grounding point anywhere on the vehicle.

I guess the idea behind switching the negative is that if a wire were to fall off or some metal piece of the truck were to come into contact with the terminals on the switch, you wouldn't have a short circuit and blow a fuse.

One reason Toyota switches the negative on the fog light circuit is they pick up the positive side for the relay coil from the low beam contact on the headlight relay. By doing this they allow the foglights to come on only when the low beams are on and not with the parking lights only or with the high beams.

 

A good rule of thumb is negative switch whenever you can, less chance of sparks.

 

Thanks

 

Yeah I ran my hot leads to the positive side of the switch and my ground (relay/coil) to the negative lead. Most important rule is be consistent. Always wrong in a system that doesn't matter means it's always right unless you go mixy-wise for no reason.

 

Apparently somewhere along the way something changed. Maybe with the 15 models? Maybe only lighting?

Anyway, I recalled reading about this recently, and had fortunately marked the thread I read it in. Maybe helpful in this situation?

Read the 1st post in this super thread by @crashnburn80 and about 1/2 way down you'll find a testing procedure to determine what you have.

 

I think the most important part is the OP knows the switch should not be driving the light, a relay should.

 

Depends on the amount of power pulled. For a 500mW LED strip light not really needed. For a 100W Off Road Light, most definitely.

 

Great point actually.

 

It's the relay coil side that's "negatively" switched...

Most switches used here in the forum that resemble OEM are of 20 to 30 amp capacity not needing a relay.
I agree that having a large gauge wire and a high amp switch coming and going into the cab is very contrary to contemporary accepted method.

Most folks here have overbuild harness's to actuate the .01 amp coil side and worst yet, a higher fuse than the actuated circuit requires negating the protection they seek. Example are the fog taps and other closely resembling modification/additions.