# Getting My Aux Back Up Light On A Switch



## DeereFarmer (Dec 12, 2005)

I've been searching on here and havn't found exactly what I'm looking for. right now I have four tractor lights mounted on my truck for reverse lights. I have them wired into a relay. They work great. What I want to do now is add a switch so I can have them on all the time, off, then on only with the stock reverse lights. I guess I need a single pole double throw switch? Anyway, I'm using the stock reverse light wire right now as the trigger on my relay. How involved would it be to add a switch at this point or shousl I just leave it alone? Thanks.


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## BoyneCityGuy (May 7, 2009)

It is really not too difficult at all...get a SPDT switch, use your current trigger wire on one pole and a 12V hot as your constant burn trigger on the other pole, then the center pole is your trigger to the relay where you currently have the reverse wire. mount the switch in the cab and your set!!

it is REALLY convenient to have them as cargo lights too, or to be able to turn them all off. i have 4 as well, 2 in the hitch that are reverse only, and 2 on the rack that are switched like you say. havent gotten the relay on this truck yet as i was in a hurry, but my last truck had it, and its a huge difference IMO. my advice is grab a beer and go do it! 

hope that helps, feel free to shoot me any questions!


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## wkahler (Mar 15, 2008)

BoyneCityGuy has ti down pat if not look up Dissociative......... [email protected]


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## DeereFarmer (Dec 12, 2005)

Thanks guys. Just want to go over it a little... would I have to run a wire all the way from the reverse light into the cab or is there an easier way? So borken down I'll have one pole used for the stock reverse light wire, the opposite pole will have the constant 12V (from the battery I'd assume), and then the center pole will have a wire run back to the trigger on my relay (#85 on the relay). Should I fuse the 12V power lead? If so what amperage? What gauge wire should I use? Seems pretty simple otherwise! Thanks again.


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## Dissociative (Feb 28, 2007)

ok...

SPDT CENTER OFFswitch.....it goes ON-OFF-ON

top terminal- in from reverse wire
center terminal- out to trigger on relay
bottom terminal- 12v source for forced on 

if i am right this will allow you to place switch in middle for a all dead and top for reverse action with bottom being the force on. 

NICE ADD ON.......find your DOME LIGHT wire....put a diode (one way valve) on a wire so the dome light can trigger the lights in the reverse action position without the reverse action turning on dome....that way when you unlock your truck....or open the doors your reverse come on too....kinda nice IMO....i love it...my reverse lights, under body lights, fogs all come on with key remote. 

If you grab your power, reverse, and add one extra wire to it for the return from switch..(pull 3 wires) to the rear if your relay is mounted back there.....

HINT.....use a strobe wire.......works VERY nicely....


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## 2COR517 (Oct 23, 2008)

Dissociative;910135 said:


> ok...
> 
> SPDT CENTER OFFswitch.....it goes ON-OFF-ON
> 
> ...


That should work just fine...

Going to set mine up that way.


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## BoyneCityGuy (May 7, 2009)

Dissociative nailed it on the head...as for your wire guage question, i went 14 and it seems to be perfect. i had guys say i could do 16 or 18, but that just seems too tiny...JMO...but that should do it for ya! and as Dissociative said with the diode, its pretty slick to have them all come on. my NBS chevy does that automatically with the reverse and cargo lights, the only annoying thing is that i have 4 extra backup lights, so if i forget to switch off the 2 on the rack, it can be almost too bright just to walk up to...i love having my hitch lights come on though!

one edit though if you set the wires up as Dissociative said, the center will be off, but up will be force on and down will be reverse. at least thats how my switch is, you have to put the wire you want to activate on the opposite terminal so it makes contact. not a big deal, but just a thought. 

ok, sorry for rambling on...go get those lights in!! post pics when you are done!!


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## T&M SnowMan (Sep 29, 2008)

Im gonna change how my aux back ups are wired when I put in my new Whelen hide-a-ways in a few weeks...always wanted to wire it up to a toggle in cab...you gotta love this place...loaded with knowledge and useful info..!!


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## Maine_Train (Dec 16, 2009)

Not to hijack your thread, DeereFarmer, but after reading this, I went to searching for the setup I'd seen that has a "guide" behind a trailer hitch ball. I think there's one out there with lights as part of it. This item (the receiver bar, #7306) popped up on J.C. Whitney's site, so I got the manufacturer's part number and went direct to the source. KC HiLiTES 2x6 Back-Up/Flood Lights
Item #6303 is the optional switch kit "that allows you to manually operate the lights in conjunction with coming on automatically with the back-up system."

Whaddya think, guys?


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## maelawncare (Mar 4, 2004)

Awe a switch kit that comes with a manual for wiring. BUT IT NOW!!

Well i just looked. And you have to buy the switch kit and the wiring harness. So its $60. Considering all the parts can be bought for $10 if you already have the wire it not that good of a deal.  darn


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## c.schulz (Dec 21, 2004)

Here ya go. So simple a child like me can do it.


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## DeereFarmer (Dec 12, 2005)

Thanks for the diagram. I've been looking for that for a while. I had it saved at one point, but lost it.


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## maelawncare (Mar 4, 2004)

c.schulz;913250 said:


> Here ya go. So simple a child like me can do it.


So what does the 87A do?


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## Thermos017 (Dec 16, 2009)

maelawncare;921412 said:


> So what does the 87A do?


that post passes power from the +12 fused supply when the relay is not energised. you can get a relay that doesn't have that pin (but works the same for this app.) and save a buck or two.


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## Dissociative (Feb 28, 2007)

that post would say go to a green light that says its safe.....then when you activate relay to turn on a dangerous item the green light goes off....and red comes on..


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## 2COR517 (Oct 23, 2008)

The relays with the 87a terminal are SPDT. Single pole DOUBLE throw. The 87a term is the normally closed contact. So when the relay is not energized, the contacts between 30 and 87a are closed, allowing current to flow through. These are the type of relays used in the older Fisher MM headlight harnesses, for example. Headlight power goes into 30. Truckside lights are connected to 87a, plowside lights are connected to 87. When you connect the wiring harness, the relays are energized transferring power from the truckside lights to the plowside lights.


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## maelawncare (Mar 4, 2004)

So for us running lights we dont need one with a 87a. good to know


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## 2COR517 (Oct 23, 2008)

maelawncare;922185 said:


> So for us running lights we dont need one with a 87a. good to know


you are correct sir


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## Bernie Lomax (Mar 15, 2007)

OK, help please. 

First off, whoever made that drawing, thank you very much. HUGE help. 

Now, all my connections are done, and lights mounted. I have power at the switch. I have power at the relay. The power is not going across the relay and out to the lights. If I remove the relay and use a jumper wire, then I have power but still not to the lights. 

Do I have a bad ground at the relay? 86 can just be grounded to the chassis, correct? 

The lights are mounted to my Back Rack and I grounded the lights to their mounting bolts on the rack. 

I'm frustrated....


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## elite1msmith (Sep 10, 2007)

question.

Does the relay work at all, either in reverse or when you flip your switch to the run mode?

could be bad ground. could be bad relay.


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## Bernie Lomax (Mar 15, 2007)

No, I never got the lights to turn on in any capacity.


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## SafetyLighting (Jul 23, 2005)

Well, first off, using the bolts that are securing the backrack does not guarantee a good ground. As for the relay ground, where is the relay located?


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## Bernie Lomax (Mar 15, 2007)

I was worried about that. But with a test light, I'm not getting power there either. 

The relay is under the dashboard on the drivers side.


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## SafetyLighting (Jul 23, 2005)

So you have power at terminal 30 on the relay, Terminal 86 is grounded. What happens when you put 12 volts to Terminal 85?

Not to discourage you from figuring it out yourself, but I will be at my shop tomorrow if you want to take a ride. I can troubleshoot a lot better when I can see the truck.


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## Bernie Lomax (Mar 15, 2007)

I didn't try that. I jumped from 30 to 87 to see if the relay was bad, but that did nothing either. 

Do you have a "go to" spot to ground in the GMT900 trucks? I initially used one of the bolts that holds the accelerator assembly to the firewall, but I think that might be aluminum. Then I tried a self tapping screw to the body over near the e-brake. 

I appreciate the offer! I'll get it figured out somehow, I was in a rush to be somewhere tonight and gave up on it a little early. 

I think it's gotta be the ground for the relay.


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## c.schulz (Dec 21, 2004)

You are welcome for the drawing!!! Yes it seems that the ground for the relay might be the problem. But I would make sure the ground for the lamps runs back to the frame of the truck not the rack.

Chris


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## SafetyLighting (Jul 23, 2005)

Well you may have a bad ground on the relay, but it doesn't sound like that is your only issue.

For the relay any low current ground will work. The self tap screw should work fine for that. put 12 volts to 85, the relay should activate. You'll hear it click.


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## Bernie Lomax (Mar 15, 2007)

Even if the ground on the lights was bad and the relay was grounded correctly I would still get power at the lights using my test light, right?


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## Bernie Lomax (Mar 15, 2007)

OK, thanks guys.


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## MSS Mow (Mar 19, 2006)

ok, I feel really dumb reading all these posts. I have no clue when it comes to wiring. lol


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## SafetyLighting (Jul 23, 2005)

MSS Mow;962222 said:


> ok, I feel really dumb reading all these posts. I have no clue when it comes to wiring. lol


Everyone starts somewhere. Spend some time reading here and asking questions, you'll be installing your own equipment in no time.


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## Bernie Lomax (Mar 15, 2007)

Power and ground are good. If I touch them the fuse blows. 

If I put the 12v+ to the 85 terminal nothing happens, and I've tried 4 different relays. I thought I heard the first one clicking, but I could have been dilusional. Taking first sip of coffee now.


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## SafetyLighting (Jul 23, 2005)

What happens if you move the flood light wire to terminal 87a?

I'm assuming you have a SPDT relay.


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## Bernie Lomax (Mar 15, 2007)

I am wired exactly like the drawing. I have a SPDT switch, maybe I have the wrong relay? I only have 4 wires in my relay.


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## SafetyLighting (Jul 23, 2005)

Your relay has four wires or do you mean it has four terminals?

What is the model number of the relay?


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## SafetyLighting (Jul 23, 2005)

You know I'm only 45 minutes away right? LOL.


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## Bernie Lomax (Mar 15, 2007)

Yeah but now I'm at my shop in Peabody, so I'd have to catch a ferry and a connecting flight to you!


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## Bernie Lomax (Mar 15, 2007)

The relay has 5 terminals, the plug for the relay has 4 wires.


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## SafetyLighting (Jul 23, 2005)

LOL, okay.


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## SafetyLighting (Jul 23, 2005)

Well electricity is like plumbing, start at the beginning and work towards the lights. Where did you get power from, the battery?


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## Bernie Lomax (Mar 15, 2007)

My wiring now is

87- out to lights on rack - power tests good at the lights
86- grounded - ground is good
30- pos from battery with fuse - power is good
85 - to center post on SPDT switch
87a - nothing

On switch,

top post is reverse wire from trailer harness - i know this is good because I put the 12v + to it and the reverse lights came on 
middle is to 85 on relay
bottom is tapped to the same wire going to post 30 on relay - which tests good


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## SafetyLighting (Jul 23, 2005)

Did you crimp with butt connectors or solder? Your circuit layout is right. You said when you jump 30 to 85 the relay still doesn't activate?


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## Bernie Lomax (Mar 15, 2007)

Thats correct. No clicking.


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## Bernie Lomax (Mar 15, 2007)

If I'm jumping 30 to 85 and have nothing then I have a bad relay? I've tried 4 different relays and I find it hard to believe they are all bad, but I'm going to go get another one.


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## SafetyLighting (Jul 23, 2005)

but when you jump 30 to 87 the lights don't activate either?


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## Bernie Lomax (Mar 15, 2007)

That works, jumping 30 to 87. I just ran out and got another relay and still have the same problem. 

So with the switch eliminated, if I just put power to 30 and 85 I get nothing.

And if I put the truck in reverse and the reverse trigger wire to the 87 pin the flood lights come on. 

I am baffled.


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## SafetyLighting (Jul 23, 2005)

Do you have crimp terminals? Female quick connects?


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## Bernie Lomax (Mar 15, 2007)

They are all crimps with heat shrink. 

Given the above, where would I look for faults? 


I gave up and just wired them to a standard switch.


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## SafetyLighting (Jul 23, 2005)

I really think your relay connector may be damaged/faulty.

I would take the relay connector out of the mix. Attach the wires right to the relay.

I'll be working tomorrow at 11 if you still don't have it working.


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## SafetyLighting (Jul 23, 2005)

What is the rating on your switch?


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## Bernie Lomax (Mar 15, 2007)

Yeah already ditched that and went direct to the relay. 

The switch isn't even connected and it's not working. With 12v power to 30 and 85 I get nothing. But if I put 12v power to the 87 the lights work. 

if I touch the wire I tapped into the trailer reverse to the 87 pin the flood lights come on.

So the power is not going across the relay no matter what I do.


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## SafetyLighting (Jul 23, 2005)

What happens when you put the light output on 87a?


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## SafetyLighting (Jul 23, 2005)

"top post is reverse wire from trailer harness - i know this is good because I put the 12v + to it and the reverse lights came on 
middle is to 85 on relay
bottom is tapped to the same wire going to post 30 on relay - which tests good"

I was re-reading your post above. Did you apply power to the trailer reverse wire, and the regular reverse lights came on? 

Is your switch rated for 10 amps continuous duty? If it is, you don't even need the relay. Just hook the Lights directly to the common terminal, where you had the relay input connected.


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## Thermos017 (Dec 16, 2009)

this may be a dumb question, but are you sure your switch works? or are you sure you have the right switch? have you checked the voltage going from the switch to pin 85? also, are you sure you're getting voltage to the switch from your primary (ignition or battery) source? if you wired the lights according to the diagram, and putting the truck in reverse makes the lights come on, then i would suspect the switch and/or wiring at the switch, not the relay. be sure your switch really is a SPDT switch. do a continuity test on the switch. just because it has 3 posts on the back does not necessarily mean it's SPDT. some lighted switches use a 3rd post as a ground to activate the light, and trying to use it as an SPDT won't work to activate a relay the way it's wired. also, not all switches operate in the same way as described earlier. in fact most switches, when the toggle is up, are connecting from the center post to the bottom post, as opposed to the way it was stated in earlier posts.

if your switch is lighted this is most likely the intended wiring for the switch:








for this switch, L1 is the ground for the light inside the switch. using it as a load or source line will not send voltage to the Common post. In fact, most switches using this wiring will burn out if you attempt to add +12V to L1.

if your switch is truly a SPDT then this would be the proper wiring:








L1 and L2 are your sources (constant +12V, and B/U light source), while 'Com' should be wired to pin 85 of your SPDT Relay.


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## SafetyLighting (Jul 23, 2005)

Thermos, I understand what you are saying, but he needs a Double Throw switch, not a Triple Throw switch. A Triple throw switch has a common input and three distinct outputs. Again, your thinking is correct, but you are confusing your switch types.


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## Thermos017 (Dec 16, 2009)

*EDIT:*


SafetyLighting;963061 said:


> Thermos, I understand what you are saying, but he needs a Double Throw switch, not a Triple Throw switch. A Triple throw switch has a common input and three distinct outputs. Again, your thinking is correct, but you are confusing your switch types.


you are right... i did put the wrong switch type in the post. however, everything i said about the switch operation applies to the SPDT switch. i have edited my previous post to reflect SPDT rather than SPTT. thanks for bringing that to my attention.

*Original:*
Well that figures. I took too long creating my post and now there is info that completely nullifies my previous suggestions. oh well, i'm going to continue my info about switches to clarify the confusion that was delivered on page 1 in this thread. the following diagrams show a cut-away of a normal SPDT switch (on-off-on), and it's operation.

In the following diagrams, the blue line inside the switch represents the contact plate, that makes electrical contact between the common post and L1 or L2 posts. The contact plate rocks from one side to the other on the common (center) post inside the switch. As you can see in the pics, when you position the switch up, the contact is created between the center and lower post on the switch, not the way described on page 1 of this thread. This is generally the normal operation of almost all toggles and rockers. when you are testing your lights check them with the toggle in all three positions to be sure you know what type of operation your switch has.

Here is a normal SPDT switch in the OFF (center) position:









and here is the same switch in the L1 ON (down) position:









and finally, the same switch in the L2 ON (up) position:


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## SafetyLighting (Jul 23, 2005)

So, how did you make out Bernie?


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## Bernie Lomax (Mar 15, 2007)

I gave up. They are wired to a regular switch and the relay and wires are zip tied up under the dash. Some day I will tackle it again. Too frustrating. 

I greatly appreciate your help though. Thank you!


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