Okay, so I've got a wire coming from the battery, and a wire coming from the two tractor lamps I've got bolted on to the back of the truck. To control the lights coming on, I have a relay behind one of the tail lamps, with a vampire clip attached to the reverse light to activate the relay. The relay ground is attached to the screw holding the relay to the truck. The relay itself is in a plastic casing.
First of all, the lights aren't working. Otherwise this post wouldn't exist. The thing is, when you take the power wire (direct from battery) and jump it to the wire going to the lights WITHOUT being anywhere near the relay, the relay clicks. The lights don't turn on. This only happens if 85 & 86 (the vamprie clip and ground) are both plugged in. The relay doesn't click when the backup light turns on.
WTF??

 

Okay, so this is how it should be set up.

Relay clip # 30 = The power from the battery to the relay (fused please!!)
Relay clip # 87 = Power wire going to your lights
Relay clip # 85 = Ground (make sure you have a GOOD ground)
Relay clip # 86 = wire going to your switch, or the exsisting reverse light power wires.

The relay should click like you mentioned, once power has been introduced. Are you sure you have a good relay? Double check your wiring connections and this "vampire" clip...

 

That's exactly how I set it up. I think I actually used a diagram you posted in another thread... anyway, the relay's good, the power's good, and the lights are good. I'm gonna recheck the grounds tomorrow, and hopefully all will be well. Also, is there a reason 30 has to be the power and 87 the lights? Since it's just a switch, can't 87 and 30 be interchanged?

 

Mine are wired like this...

87---15amp fused 12v supply.
86---trigger wire. (Existing back up lights)
85---Ground.
30---New lights.
As said above, make sure the ground connection is 100%.

 

Terminals 30 and 87 can be interchanged as can 86 and 85. The terminals are numbered though in order to conform to standards and also to prevent confusion to someone else who may be working on the system.

I would guess that you have something wired up wrong on the relay. It should have a picture / schematic printed on it showing the terminals and circuitry.

You want the wire from the stock reverse lights and the relay ground connected across terminals 85 and 86 and the power from the battery to 30 and the lead to the add-on lights to 87.

 

OK, that's what I thought. The relay is wired up 100%, and it actually kind of works now that I cleaned up the ground connections on the lights themselves. If I take a jumper cable and ground one of the lights to the frame, they both work perfectly. But without the jumper cable, nothing happens. I'm guessing now that the relay ground is bad.

 

If grounding one of the lights directly to the frame fixes the problem, your light grounds are bad.

1. Remove the ground you have setup for the relay. I have seen it fail when routed like that. Route to a factory ground if possible..

2. Remove and improve the grounds on the lights. Are they mount/grounded?

 

They are mount/grounded, same as the lamps you got I think. If the light grounds are bad, why would grounding only one of them properly make both work? The lights are wired in parallel.

 

Resanding down the relay ground mount didn't help...You really think it's the light grounds?

 

Well, if you grounded the lights to a good ground and they worked. It means the current ground is not good enough. Make sure your grounds have a clear path to the frame. And ground your relay to a factory ground or better ground.

Thats all I can really think of without being there.... sorry

 

I recently had this problem on only one of the lights I installed. After much trial and error, it turns out that there's a connector under the sheathing coming directly behind each light. The power wire on each was disconnected. Why there's a connector point instead of a solid wire lead, I have no idea. Just a thought.

 

Thanks for all the help. I'll try using a wire to ground it rather than just the mount points since it doesn't seem like the mounts are good enough. What a pain in the ass... Hopefully I will soon be able to see where I am going in reverse.

 

I finally got the damn things to work today... wired an extra ground from one of the lights to the stock rear ground point, and voila, perfect. I would still really like to know why grounding one light makes them both work, though. Any electrical engineers lurking the forums who wanna share some insight with me?

 

does each light have it's own ground? if not when you ground one, you actually ground them both through the shared wire. -or- the light has a good ground to whatever it's mounted to, but whatever it's mounted to does not have a good ground to the chassis, so by grounding one light you are really grounding the bumper/whatever and the other light

 

Ah hah!! It didnt occur to me that the body had to be grounded to the frame...I figured that it was enough that they are touching, but theres rubber between the body and the frame...where are the body ground points located on a 3rd gen, do you know?

 

Is it not easier to simply hook into the stock reverse lights? That's what i'm going to do.

 

it is MUCH easier to hook them into the stock reverse lights, but the OEM wiring isnt designed for the added load of two 50W lights so it could end up being dangerous. It would work as a temporary measure, but getting underneath and routing wire with sand and dirt falling into your eyes and hair and getting grease up to your elbows is the better way to do it.

 

Exactly, plus with the stock wiring is small as it is. You won't get as much power to the lights.

Plus the proper way (no fire fire) is to wire in a relay.

Glad you got it to work

My reverse lights are mount grounded and my bumper works fine...

 

That's what I did several years ago. Very easy! One of my lights finally rusted out and I'm looking to replace them....the same way.