# Toggle switch cuts power to 6v



## yardsmith (Jan 3, 2000)

Hey gang- working on my plow truck, going over everything for the upcoming season. I have an LED back up light mounted on the rear of my truck. Everything worked fine until a week ago- light quit workjing, but the indicator light on the toggle switch was still on. Checked voltage & I only have 6v at the light. I checked voltage at the switch, & I have 12v coming in between power & ground, but when I turn the switch on it cuts it & only puts out 6v at the switch.
I replaced the toggle switch with a new one, & same results.
I have cleaned the ground back by the light, & still same results.
Any ideas???
Thanks


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## dieselss (Jan 3, 2008)

Check the power source to the switch.


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## cwren2472 (Aug 15, 2014)

What @dieselss said - the voltage drop means the lead from the battery can't provide what the light is drawing. Either loose/bad connection, too small of a wire, too long a run, etc.


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## theplowmeister (Nov 14, 2006)

Since it was working its not likely to be too small a wire or too long a run. since the voltage drop happens before the switch so is the problem. when u installed the wiring did you solder the connections? If not corrosion can wrack havoc on them. A pin hole in the wire can let water in and cause corrosion. If you did solder the connections did you clean off the Flux? Flux is a corrosive and continues to work after you finish. In line fuse corroded?


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## yardsmith (Jan 3, 2000)

Just using spade terminals like all the other ones I've wired in the past.
voltage across the power & ground at the switch is 12v. Once I flip the toggle on, voltage at those same two terminals is 6v. I put in a diff / new toggle switch & I get the same.
It's only a 3W LED bulb which draws very little power, & the same setup has worked on my plow trucks over the years just fine. Not sure what triggered the change. It worked fine until a few weeks ago. Now I'm getting half the voltage.


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## yardsmith (Jan 3, 2000)

I have a bit of dialectric grease on the spade terminals to keep things from oxidizing. I will clean & recheck them tomorrow


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## dieselss (Jan 3, 2008)

Whats the voltage at the switch "in" 
And whats the voltage at the switch "out"?
You need to test this using straight battery voltage.
How is the light grounded? Have you verified that its a good ground by testing straight from the battery?

What fuse is the power wire tapped into?


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## Randall Ave (Oct 29, 2014)

At the power going into the switch, what I have done in the past for a test is use a headlamp. Can be a pain for a test but at least you know if the source is good or bad.


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## cwren2472 (Aug 15, 2014)

have you tried a different light? If the light is shorting out internally, that can also cause your voltage drop


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## theplowmeister (Nov 14, 2006)

if the LED is shorted and causing a 6V drop. the current draw would be heating up the wire. supply wire has high resistance due to brake/corrosion.

un hook the LED hook in a 1156 bulb in place of the LED and measure voltage at the switch.


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## Hydromaster (Jun 11, 2018)

A Digital Clamp ammeter Multimeter Voltmeter 400A Electronic Clamp meter will answer your question.


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## JoeRagMan (Nov 5, 2018)

Check the wiring at the fixture, LED’s are usually polarity sensitive. Is it pot that the lamp is wired backwards? Good luck.


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## yardsmith (Jan 3, 2000)

Even when I test the wires at the back of the truck, isolated before / without the light, they are reading 6v with the switch on, so I think that would eliminate the light being bad. Guess I'll hook up some short wires to another light & see if it's any different.
There are red & black wires coming from the light, so everything is correct.
The circuit / light is grounded at the light, not at the switch. I have always done it that way per the schematic from the LED manufacturer.
The 12v source is from an open pole available at the fuse box.
Guess I will try another light just to be sure


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## yardsmith (Jan 3, 2000)

dieselss said:


> Whats the voltage at the switch "in"
> And whats the voltage at the switch "out"?
> You need to test this using straight battery voltage.
> How is the light grounded? Have you verified that its a good ground by testing straight from the battery?
> ...


Voltage coming in, & across the terminals (with toggle off) is 12v.
When I turn the switch on, voltage across same terminals is 6v


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## dieselss (Jan 3, 2008)

And your ground is good? How have you checked it?

Take the lead off the light at the switch and see what you get


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## theplowmeister (Nov 14, 2006)

You are making this way to hard. there are only 6 components to test.
1)Power lead to switch
2) switch
3) wire from switch to LED
4) LED
5) led ground.
6) supply voltage

you must have a test light.

replace LED with the test light (the test light will have an alligator clamp ground find a good ground)

run a peace of wire from the switch output to the LED

touch the supply wire to the output wire of the switch

run a test wire from batterie to switch

mesure the voltage AT the supply wire where it taps in, where it gets its juice (not batterie) flip switch

Those 6 steps is all thats needed


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## yardsmith (Jan 3, 2000)

The light does not require a ground at the switch, only at the light for it to work normally. I will prob have to add a ground at the switch side too.
I use my fluke style voltmeter for my electrical work


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## cwren2472 (Aug 15, 2014)

Remember that presence of 12v does not mean anything unless its under a load (therefore, switch is on with light drawing)
You could hook a 12,000 lb winch up to a battery with a 14gauge wire and the multimeter will show 12v coming in just fine but it doesn't mean everything is working correctly


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## Hydromaster (Jun 11, 2018)

When you say led.
What requirements does it have.
I run my led light ( jagoffbar )useing a switched relay .

A lot of switches will burn, melt, have to mulch resistance for the load.


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## cwren2472 (Aug 15, 2014)

Hydromaster said:


> I run my led light ( jagoffbar )


I dont believe it - we need jagoff light pics for proof


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## dieselss (Jan 3, 2008)

yardsmith said:


> I will prob have to add a ground at the switch side too.


Why?


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## JoeRagMan (Nov 5, 2018)

If the rocker switch has an internal light doesn’t it need a separate ground to illuminate? Otherwise, the voltage is cut in half not allowing the LED worklight to light up?


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## Mr.Markus (Jan 7, 2010)

How much is the amperage draw on your light? If its just a back up light why isnt it just wired into your reverse circuit at the back. Easy peasy, on in reverse and you never forget to turn it off. No wiring to the cab or switches needed.


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## SHAWZER (Feb 29, 2012)

That is how I hooked my 2 led lights at the back of the truck . Never had a problem for 5 years now .


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## Hydromaster (Jun 11, 2018)

cwren2472 said:


> I dont believe it - we need jagoff light pics for proof


This isn't about my jagoff light.
Sew, try to stay on topic, thanks.


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## yardsmith (Jan 3, 2000)

light is putting out 1.1 amp @ 13-18 watts
Here is the link where I buy them
https://www.online-led-store.com/la...ed-light-bar-60-degrees-flood-orzledlbr104-fl


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## yardsmith (Jan 3, 2000)

I need it on a separate switch for many reasons. I use it as a flood light when camping, when throwing salt to make sure it's coming out properly, etc. I use it for much more than backing up


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## yardsmith (Jan 3, 2000)

Someone I talked to the other day said it may need grounding at the switch in case my ground out back at the light isn't a good enough ground


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## Randall Ave (Oct 29, 2014)

You need to check the supply voltage at the switch. First voltage, then as stated before connect a lamp that will put a draw on the supply voltage like a 1157 bulb, I use a headlamp. Don't use anything LED.


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## cwren2472 (Aug 15, 2014)

yardsmith said:


> Someone I talked to the other day said it may need grounding at the switch in case my ground out back at the light isn't a good enough ground


Curious - how exactly do you ground the light to the switch ?


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## Randall Ave (Oct 29, 2014)

cwren2472 said:


> Curious - how exactly do you ground the light to the switch ?


It uses the third style of polarity.


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## yardsmith (Jan 3, 2000)

I would splice in a ground near the switch, & mate it to the spade terminal at the switch, then I would also have the ground back at the light


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## theplowmeister (Nov 14, 2006)

Ill say it again 
if you get 6V at the switch it has to be a problem between the switch and the batterie.


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## TJS (Oct 22, 2003)

Did you try a simple toggle switch without the indicator light, like plowmeister is saying.


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## dieselss (Jan 3, 2008)

yardsmith said:


> I would splice in a ground near the switch, & mate it to the spade terminal at the switch, then I would also have the ground back at the light


Are uou sure your putting the wires in the switch in the correct pins?
Let's get a picture of the switch.


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## Avalanche 2500 (Dec 31, 2015)

For a new install or you could start over, I would use a Relay Thumbs Up >>
https://www.youtube.com/watch?v=qTZDmql8ctA


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## yardsmith (Jan 3, 2000)

I will be working on it again tomorrow; will get updates posted. Thanks everyone.


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## yardsmith (Jan 3, 2000)

toggle I am currently using looks like this


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## yardsmith (Jan 3, 2000)

Alright it's fixed guys. Woo hoo! 
I added a wire to the ground at the switch, & grounded that under the dash. Everything works as it should. I guess the ground out back at the light wasn't good enough.
Thanks for your help everyone.


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## dieselss (Jan 3, 2008)

Post a pic of your switch


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## theplowmeister (Nov 14, 2006)

Thumbs Up


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## dieselss (Jan 3, 2008)

Any pictures coming soon?


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## Randall Ave (Oct 29, 2014)

Hey if it is working, great. But connecting a ground wire to the switch should have no bearing on the lamp working.


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## dieselss (Jan 3, 2008)

Randall Ave said:


> Hey if it is working, great. But connecting a ground wire to the switch should have no bearing on the lamp working.


Eggzackly, something just don't seem right


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## JoeRagMan (Nov 5, 2018)

OP stated that switch had a lamp which came on when activated. Without a ground for that lamp, there was two lamps (switch lamp and LED lamp) in series. Which caused each lamp to get 6 volts. Adding the ground at the switch allows 12 volts to the LED lamp. Thinking that 6 volts was not enough to illuminate the LED.


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## theplowmeister (Nov 14, 2006)

Nope sorry the switch light and the backup light are in parallel NOT series



JoeRagMan said:


> OP stated that switch had a lamp which came on when activated. Without a ground for that lamp, there was two lamps (switch lamp and LED lamp) in series. Which caused each lamp to get 6 volts. Adding the ground at the switch allows 12 volts to the LED lamp. Thinking that 6 volts was not enough to illuminate the LED.


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## cwren2472 (Aug 15, 2014)

JoeRagMan said:


> OP stated that switch had a lamp which came on when activated. Without a ground for that lamp, there was two lamps (switch lamp and LED lamp) in series. Which caused each lamp to get 6 volts. Adding the ground at the switch allows 12 volts to the LED lamp. Thinking that 6 volts was not enough to illuminate the LED.


That isn't how voltage works - it is no different than adding a second light to the circuit. The voltage doesn't drop in half because you are powering two lights, not one, only the total AMP draw would change (assuming the amps drawn by the led in the switch even mattered.) These are not christmas tree lights. The only affect would be that the light on the switch would not light up as it didn't have a ground, same as a second light connected to the circuit would not light up without it's own ground.

Edit: or what @theplowmeister said above too


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## JoeRagMan (Nov 5, 2018)

If there isn’t a ground wire for the first lamp, it will cut the voltage in half. Try it at home, set up two incandescent lamps on a work bench. Hot wire to one terminal of a lamp, other terminal to the next lamp. Then connect last terminal to the neutral. That is a series circuit. 
House wiring, DC wiring, same theory.


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## cwren2472 (Aug 15, 2014)

JoeRagMan said:


> If there isn't a ground wire for the first lamp, it will cut the voltage in half. Try it at home, set up two incandescent lamps on a work bench. Hot wire to one terminal of a lamp, other terminal to the next lamp. Then connect last terminal to the neutral. That is a series circuit.
> House wiring, DC wiring, same theory.


That is true because they would be wired in parallel as stated above. That is not how the lighted switch works.


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## JoeRagMan (Nov 5, 2018)

But if that lighted switch doesn’t have a separate ground, the switch lamp is now in series with the LED fixture.


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## theplowmeister (Nov 14, 2006)

After you get a BS in Electronics come back and explain how this works.

so If the lighted switch has no ground it re wires* itself* to go from parallel to series! 
by removing the thin black line from the switch to ground the internal switch changes to series?

No the switch light is just left hanging. with a terminal to no where. Power still flows to the load (Backup light)












JoeRagMan said:


> But if that lighted switch doesn't have a separate ground, the switch lamp is now in series with the LED fixture.


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## JoeRagMan (Nov 5, 2018)

So if there was only a SPST switch controlling the circuit, 12 volts would be supplied to the LED lamp. But with a lighted switch in the circuit, the current has to go through the switch lamp first. Without a ground terminal on the switch to complete the circuit for the switch lamp, only half of the voltage will be available at the LED lamp.


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## dieselss (Jan 3, 2008)

His switch has a separate pole for the light in the switch, (i have the same type of switch) so unless he wires it wrong,...simply putting power in and power out on the correct poles will not activate the light on the switch.


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## Randall Ave (Oct 29, 2014)

JoeRagMan said:


> So if there was only a SPST switch controlling the circuit, 12 volts would be supplied to the LED lamp. But with a lighted switch in the circuit, the current has to go through the switch lamp first. Without a ground terminal on the switch to complete the circuit for the switch lamp, only half of the voltage will be available at the LED lamp.


NO


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## cwren2472 (Aug 15, 2014)

JoeRagMan said:


> So if there was only a SPST switch controlling the circuit, 12 volts would be supplied to the LED lamp. But with a lighted switch in the circuit, the current has to go through the switch lamp first. Without a ground terminal on the switch to complete the circuit for the switch lamp, only half of the voltage will be available at the LED lamp.


The circuit that illuminates the led is in parallel with the rest of the circuit. The current does not flow "through" the led. The led steals a small amount of current. The led is no different than a second light wired along side the primary light on the same circuit. That second light has no effect on the primary light. I really have no idea how else to explain it more clearly


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## JoeRagMan (Nov 5, 2018)

So going on the OP’s information he said he only had 6 volts at the LED. When I asked if the switch needed to be grounded he tried it and the LED worked? Tough to diagnose on a computer screen...


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## yardsmith (Jan 3, 2000)

Dieselss, the switch is pictured two posts above yours ^^^


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## yardsmith (Jan 3, 2000)

Here is my before & after schematic


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## dieselss (Jan 3, 2008)

So the ground out back is what sent the ground to the switch.. so that was probably not a good ground.

Why no pictures of the exact setup?


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## cwren2472 (Aug 15, 2014)

yardsmith said:


> Here is my before & after schematic
> View attachment 207966





JoeRagMan said:


> So going on the OP's information he said he only had 6 volts at the LED. When I asked if the switch needed to be grounded he tried it and the LED worked? Tough to diagnose on a computer screen...


Assuming everything said is accurate, my only conclusion is:

1) Obviously the drawing above is not 100% correct because the battery negative goes to nothing. That would never work. But we can assume the battery is grounded to the frame somewhere even though he didn't draw it

2) the light was originally grounded only to the frame - the ground point was inadequate to ground the light resulting in a voltage drop as the light tried to work. Edit: oh, and what @dieselss said above. Dang it.

3) the OP added a second ground to the frame - coincidentally at the switch but it could have been anywhere. The allowed the light to work. It has absolutely nothing to do with the LED in the light magically sucking 6 volts from the circuit due to a lack of ground. Had the switch been unlit, the effect would have been exactly the same, the only difference is there would have been no 3rd post on the switch so the added ground would have been by itself


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## yardsmith (Jan 3, 2000)

dieselss- not sure what pics would show. The switch is mounted in the plastic panel under the steering wheel, & the wires run through the firewall down under the truck to the rear of the bed. The light is mounted on my salt spreader bracket, on top of the bed rail. I have a piece of coroplast between the top of the bed rail & my spreader mount bracket, so that may have been insulating against having a good ground back there, even though the bolts go through, metal to metal.

cwren, the battery is obviously grounded to the frame. Thought that was a given, & not super pertinent to the light circuit.


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## cwren2472 (Aug 15, 2014)

yardsmith said:


> dieselss- not sure what pics would show. The switch is mounted in the plastic panel under the steering wheel, & the wires run through the firewall down under the truck to the rear of the bed. The light is mounted on my salt spreader bracket, on top of the bed rail. I have a piece of coroplast between the top of the bed rail & my spreader mount bracket, so that may have been insulating against having a good ground back there, even though the bolts go through, metal to metal.
> 
> cwren, the battery is obviously grounded to the frame. Thought that was a given, & not super pertinent to the light circuit.


K


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## dieselss (Jan 3, 2008)

cwren2472 said:


> K


Nope guess where the ground is isn't super important....


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## cwren2472 (Aug 15, 2014)

Deleted


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## H3lzsn1p3r (Nov 23, 2020)

JoeRagMan said:


> So if there was only a SPST switch controlling the circuit, 12 volts would be supplied to the LED lamp. But with a lighted switch in the circuit, the current has to go through the switch lamp first. Without a ground terminal on the switch to complete the circuit for the switch lamp, only half of the voltage will be available at the LED lamp.


The switch "light" is not even needed it is just an option if you want a dummy light to show you when the switch is on, for what you are saying to be true the led in the switch would need to be in series (like small string Christmas lights) but it is indeed in parallel.... i almost never ground out my led indicator switches because i have no use for the light in them


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