Backup light help

bradjh · Post by **bradjh** » Sun Apr 20, 2008 2:00 pm

I installed a fire and ice led bar with back up lights. Today i installed 55 watt back up lights under the rear bumper.. I tapped in to the wire that i conneced the led bar to the back up lights.. now when i put it in reverse the back up lights are bright and the led bar is very dim now... How can i correct the problem? Brad

Post by **HenryJ** » Sun Apr 20, 2008 2:10 pm

Are you using a relay and power from the electrical center, or battery?
The stock wiring will not handle the load if you just tapped it for all the additional lights.

bradjh · Post by **bradjh** » Sun Apr 20, 2008 2:27 pm

i just tapped in. how do i add a relay???

Post by **HenryJ** » Sun Apr 20, 2008 3:05 pm

You do need a relay to provide the power needed for your lights. It is also a nice safety feature. The relay contains a coil and when overheated it tends to fail. This saves burning down the wiring. The one fuse at the battery or power source for the wire supplying the relay will protect the system.

12Volt.com is an excellent resource. Start with the basics: Relays

12volt.com wrote:Why do I want to use a relay and do I really need to? Anytime you want to switch a device which draws more current than is provided by an output of a switch or component you'll need to use a relay. The coil of an SPDT relay that we most commonly use draws very little current (less than 200 milliamps) and the amount of current that you can pass through a relay's common, normally closed, and normally open contacts will handle up to 30 or 40 amps. This allows you to switch devices such as headlights, parking lights, horns, etc., with low amperage outputs such as those found on keyless entry and alarm systems, and other components. In some cases you may need to switch multiple things at the same time using one output. A single output connected to multiple relays will allow you to open continuity and/or close continuity simultaneously on multiple wires.

I usually go to my quadbeam page and use the diagram I made for wiring a relay:

relay "activate +"(#85) , relay feed (Normally Open #30) , relay supply (#87) and to relay "activate - " (#86).It is not a bad idea to use a switch to ground the relay for activation. That way you don't have a hot wire passing the firewall and only one wire to the switch , as the other side of the switch can be grounded.Use the back up light wire to activate a relay. Power the relay from the electrical center.

Back-up light wiring

HenryJ wrote:I would mount a relay inside the rear frame rail near the tail light wiring. Inside the left rear frame rail there is a white plastic connection. This is the tail lamp wiring.

You can add a maxi fuse to the engine compartment fuse box to energize the rear power distribution stud, then add a wire from there to the rear of your truck to power the lights. Attach this to the relay positive power source (#87)

Tap the light green wire. This is your positive back-up light wire attach it to relay "activate +"(#85)

Ground terminal #86

#30 is where you attach the positive feed for the lights.

Adding an accessory power source

bradjh · Post by **bradjh** » Mon Apr 21, 2008 3:07 am

All this relay stuff seems like a differnt language... The lights that i purchased has an inline fuse where i spliced into the backup lights.. DO i still need a relay. Are relays hard to do i have no idea about electrial stuff..

Post by **HenryJ** » Mon Apr 21, 2008 4:13 am

You need a relay.
The wire to your back up lights is too small to handle more than 108 watts total load.
Time to do some reading of the information I posted above.

bradjh · Post by **bradjh** » Mon Apr 21, 2008 7:23 am

henry J i have read what you said and i do not fully understand. Can i get a relay at an auto parts store? What if i tapped into the taillight on the other side? Am i going to have to run wires all the way up to the cab or engine bay? BRad

F9K9 · Post by **F9K9** » Mon Apr 21, 2008 7:51 am

bradjh wrote:..........Am i going to have to run wires all the way up to the cab or engine bay? BRad

Yes, just run it off the PDC (power distribution center) It's the black box on the driver's side inner fender. Remove the cover and you will see a stud/post on the upper right. It should be already fused with a grn 30 amp maxi fuse. Attach the wire to the relay there. Personally if, I had it to do over again I would place the relay close to the PDC and run 2 wires along the frame to the back. One tapped into your back up lights and one to power the aux lights. I tend to go through relays when exposed to the elements.

green02crew · Post by **green02crew** » Mon Apr 21, 2008 11:19 am

I ran a single small fog light that I purchased at Walmart. It is bright and still fairly low wattage. I have had this system running for a while now tapped into my reverse lights without issue maybe I'm just lucky? The set of two lights was $15 and my friend and I shared the cost each putting one under our bumpers. It was a simple setup and the reverse lights are just as bright as they were before added drain. I may be borderline failure but it has worked out so far.

Post by **HenryJ** » Mon Apr 21, 2008 2:09 pm

bradjh wrote:... i do not fully understand.

Ok. Lets see if we can talk you through it.

Can i get a relay at an auto parts store?

Yes.

What if i tapped into the taillight on the other side?

That will not help. They are both fed by the same wire and the gauge is too small for the load you are adding.

Am i going to have to run wires all the way up to the cab or engine bay?

Yes.

If you get a weather proof relay you can mount it back where you tapped the back up lights and then run a wire from the electrical center to supply it.

If you want to mount it in the engine compartment, perhaps we can find a place closer to tap for a back up lights feed.