# How To Properly Wire Additional Reverse Lights?



## DeereFarmer

Don't yell at me! I've done tons of searches on this topic and now this is a very common topic, but I'm a little confused. First my '02 GMC has the factory plow prep package and towing package with the 7 round plug. I also have the factory AUX. light switch. What I want to do is mount two reverse lights under the bumper for added rear lighting. My windows are tined from the previous owner so it's hard to see to begin with.  Anyway, what is proper wat to add these lights. I don't really want to wire a switch so they are on when I want. I jsut need them on when the truck is in reverse. Can I just wire them directly into the stock reverse wires with a relay? Do I wire them into the trailer backup lights on the 7 way? I don't have any trailers with backup lights. Is there a easy way to add them into the AUX switch? That'd be pretty cool. What would you guys do?


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## BigLou80

I have the same truck and use my aux switch for my strobes. Just pull off the side panel behind the drivers seat and you will find the relay. Sorry I can't be of to much help on how to wire the back up lights although I would just find the wire for the trailer and add a relay


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## basher

If you use the reverse wire from the trailer towing package. You shouldn't need a relay unless the lights have a very high amp draw. Look on the drivers side frame between the cab and bed, there could be an accessory harness there for Gooseneck/fifth wheel applications. Normal for any General 3/4 ton with a tow package. You could splice a longer one onto that with a GOOD crimp fastener. I suggest low temp solder filled heat shrink connector.


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## yard5864

I just spliced into the 7 pin trailer connector with 2 tractor lights under the bumper and it works great with no problems.


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## basher

The 2002 chevy will have a US car connector. While it and the plug you show are the same from the trailer side the US car is a molded two piece part and has no accessible terminals. But the reverse will go to the center


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## wild bill

*lights*

here's a quick one just hooked into a 7 wire plug and plugged in at thee hitch ,look in thread any one using back up lights .


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## ChevKid03

I just put a set on the back of my 03 2500HD because of the same reason. I have BLACKED out windows that are extremely difficult to see out of at night when backing up. I ended up purchasing a set of reverse lights from the local parts store. If you have a test light, you can find the reverse light wire and wire the hot one from the new store bought lights to this. Then run a ground anywhere on the frame.


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## DeereFarmer

Thanks guys. I like the idea of wiring them to the gooseneck plug. Next time I have the truck on the lift I'll have to take a look for that. I've never noticed it before. I do have a test light and pretty much any tool I need.


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## B&B

Just a tip here for you guys running hi amp backup lights....

Do not direct wire lights into the stock reverse light circuit that will draw more than 10 amps max without using a relay.

The stock reverse light circuit is not externally relayed in these trucks and it travels directly through the reverse light switch as well as the body control module...neither of which are designed to handle more than a 10 amp additional load in addition to the stock reverse bulbs on that circuit. _*Use a relay*_.


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## famouslee99gt

I know you said you didn't want to hook them up on their own switch, but I did such on my '99 Z71 and I love that. I like to leave them on when plowing. They are also useful when hooking up trailers or wagons at night, and they'll stay on when you are in park hooking up the trailer. I personally just like having them on their own switch


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## DeereFarmer

B&B;598948 said:


> Just a tip here for you guys running hi amp backup lights....
> 
> Do not direct wire lights into the stock reverse light circuit that will draw more than 10 amps max without using a relay.
> 
> The stock reverse light circuit is not externally relayed in these trucks and it travels directly through the reverse light switch as well as the body control module...neither of which are designed to handle more than a 10 amp additional load in addition to the stock reverse bulbs on that circuit. _*Use a relay*_.


B&B, could you give me a quick lesson on relays? What do I need to buy as far as relays go? How do I wire them up? I'm new to relays and trust your opinion!

Also, how much harder would it be to run them to a switch? I jsut don't want to drill a switch into my dash and run a wire through the firewall all the way back.


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## B&B

A relay is nothing more than a remotely activated hi amp toggle switch that can be remotely activated with a low amp circuit...such as a small toggle switch with a light gage wire...or in the case of reverse lights, the factory reverse light switch. Its purpose is to carry the hi amp load from the power source to the accessory that you want to operate without having to have the hi amp power run through your tripping mechanism (reverse light switch in this case). Relays cab be wired dozens of different ways depending on what your using them for.

If you search the net you'll find hours of reading and examples of how relays work and what application to use them for. Here is just a couple quick examples I found:

Relays

Relays

Relay diagram


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## basher

you will be able to find all the wires required to use a relay with in the goose harness. the power supply, the signal and the ground are all there and readily available. use a diode if you plan to use both a dash switch and shifter to entergize them.


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## mkwl

B&B;598948 said:


> Just a tip here for you guys running hi amp backup lights....
> 
> Do not direct wire lights into the stock reverse light circuit that will draw more than 10 amps max without using a relay.
> 
> The stock reverse light circuit is not externally relayed in these trucks and it travels directly through the reverse light switch as well as the body control module...neither of which are designed to handle more than a 10 amp additional load in addition to the stock reverse bulbs on that circuit. _*Use a relay*_.


I did this (no relay) with mine- guess they draw less than 10A cause I've had em on there for almost a year- no problems (knock on wood). They are the cheap $19 ones from Northerntool- work well though


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## DeereFarmer

OK, so I've read a lot on this subject and think I have it down. I'm going with a realy for sure. Let me make sure I have this correct. There are 4 prongs to a realy. One is a hot lead from the battery, one is a ground (more than likely I'll run this from the battery as well just to be safe), one is a trigger (in this case probably run from the stock backup light, correct?), and the final one goes to the load (new backup lights). Now, here are a few more questions I have:

-to power a pair of 55W lights do I need two relays or just one?
-what gauge wire should use?
-on a standard relay how can you tell what prong goes to what function? most relays I've seen arn't marked or anything.

I'm pretty sure I'm ready to tackle this project. I've done a lot of trailer wiring and wiring for trailer hitches so I do have some experience on the subject. Just don't want to screw up my truck. Thanks guys.


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## B&B

DeereFarmer;604518 said:


> OK, so I've read a lot on this subject and think I have it down. I'm going with a realy for sure. Let me make sure I have this correct. There are 4 prongs to a realy. One is a hot lead from the battery, one is a ground (more than likely I'll run this from the battery as well just to be safe), one is a trigger (in this case probably run from the stock backup light, correct?), and the final one goes to the load (new backup lights). Now, here are a few more questions I have:


 You've got it. 



DeereFarmer;604518 said:


> -to power a pair of 55W lights do I need two relays or just one?


 A single relay is plenty for two 55 watt lights. Most generic relays will handle 30 amps each.



DeereFarmer;604518 said:


> -what gauge wire should use?


 Use 14 gage for the batt power wire as well as the wires to the lights from the relay. The ground and trigger wires can be much smaller since they carry little current, 18 gage is more than enough. Make sure to fuse the toggle switch power wire (5 amp is plenty) as well as the power wire to the battery (15 amp will do it).



DeereFarmer;604518 said:


> --on a standard relay how can you tell what prong goes to what function? most relays I've seen arn't marked or anything.


 If you look on the underside most generic relays are marked with the corresponding pin locations. If you get one that isn't you can tell just by the pin orientations if you use one of the diagrams in several of the links I previously posted.


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## cet

I know you said you didn't want to use a switch. When I put my lights on my truck I used an ON-OFF-ON switch through a relay. I can have them on all the time, everytime I put the truck in reverse or not on at all. I didn't want them on when I didn't need them and I also wasn't sure how much power they were going to use. If my truck started to get low on power then I won't use them at all. That never happened though.


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## DeereFarmer

Thanks again guys, especially B&B. What if I want to go way overboard and wire up 4 lights? I have two 35W tractor lights for under the bumper and also two 55W CAT lights that I was thinking of maybe mounting on the top of the bumper right under the stock light housings. It might be overkill, but I'm just thinking. Want to get it all planned out before I start tomorrow. Is there a relay out there that can handle 60 amps? Maybe I'm just nuts. I'm feeling confident about this install thanks to you guys!


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## B&B

Just add a second relay if you want and use your toggle (or whatever tripping method your using) to trip them both.

Most Bosch style generic relays like we're discussing here are 30 amp...some are 40. There are relays that will handle hundreds of amps but their under the solenoid classification like a snow plow under hood solenoid (which is just a large relay)...and would be way overkill for your intended application. 

A single 30 amp relay will actually support over 300 WATT but they tend to melt the wire terminals when running too many wires off each pin on the relay.


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## Bruce'sEx

cet;604613 said:


> I know you said you didn't want to use a switch. When I put my lights on my truck I used an ON-OFF-ON switch through a relay. I can have them on all the time, everytime I put the truck in reverse or not on at all. I didn't want them on when I didn't need them and I also wasn't sure how much power they were going to use. If my truck started to get low on power then I won't use them at all. That never happened though.


I've got mine on a switch at the momment, but I'm upgrading to the on-off-on system, i like the idea, and is more flexable for what I need when.


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## DeereFarmer

Well, got it done for the most part today thanks to you guys. Took my time and a lot of zip ties, but it came out great. Worked first try. The relay makes those tractor lights work to their full extent. I have never seen tractor lights to bright. I'm going to add a second pair tomorrow. Right now I have a pair mounted under the bumper facing straight out. Nothing burned up on the ride home from work (10 miles) and the relay didn't seem to get hot or anything, so I'd say it was done correctly. Tomorrow I'll add a pair on top of the bumper just below the factory taillight assemblies and face them to the side a little. Just to make sure: a 40 AMP relay will be able to power the four 35W tractor lights ok, right? What fuse should I use? A 30? I'm going to try it this way first. If there are any problems, I'll just run a second relay. 

I don't have a switch yet, but might wire one up this week. How hard will that be? I know I have to run one wire to the hot terminal of the relay, one to the trigger, and one to the stock backup light wire. now here's my dilemma. Right now my trigger is from the stock backup lights, so I'm a little confused.


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## basher

DeereFarmer;606380 said:


> I don't have a switch yet, but might wire one up this week. How hard will that be? I know I have to run one wire to the hot terminal of the relay, one to the trigger, and one to the stock backup light wire. now here's my dilemma. Right now my trigger is from the stock backup lights, so I'm a little confused.


should add a diode or two so you're not back feeding if you plan to run 2 triggers to the same relay


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## B&B

DeereFarmer;606380 said:


> Just to make sure: a 40 AMP relay will be able to power the four 35W tractor lights ok, right? What fuse should I use? A 30?


The single 40 amp relay will be just fine with the four lights.

Start with a 15 amp fuse first. If it isn't enough (should be but it depends on how long your batt hot wire is) then step to a 20 amp. You want to run the lowest amp fuse you can that will still carry the necessary load with a little room to spare. Safer that way and allows the fuse to do what its intended for.



DeereFarmer;606380 said:


> I don't have a switch yet, but might wire one up this week. How hard will that be? I know I have to run one wire to the hot terminal of the relay, one to the trigger, and one to the stock backup light wire. now here's my dilemma. Right now my trigger is from the stock backup lights, so I'm a little confused.


Several different ways to wire the switch depending how you want it to function. Do you want the relay/lights to be tripped by the trucks reverse light circuit like you have it currently PLUS be able to manually turn the lights on steady when needed?


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## DeereFarmer

B&B;606813 said:


> Do you want the relay/lights to be tripped by the trucks reverse light circuit like you have it currently PLUS be able to manually turn the lights on steady when needed?


Correct.

The second pair of lights went on great today. The only problem is one of the new lights is not working. It's getting power and a good ground. When I shake it I can hear something large rattling in there. Should have shaken it before I bought it lol. Oh well, one last trip to the truck store and all four will be wired up and working!


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## B&B

DeereFarmer;607473 said:


> Correct.


To do the the switch part is simple, just a keyed ignition wire to the switch, then out from the switch to your trip terminal on your relay...

BUT, you want to also install a diode in the current wire you have running between the relay and your trucks back up light wire, or else when you flip the toggle it will back-feed into the reverse light wire. Add it in right where you tied into the reverse light wire.


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## DeereFarmer

Great. Thanks for the help B&B. I'll have to get some pics up to show you guys what I did soon.


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