Theocoog

The way I have it wired in my original post, the lights come on when the truck is in reverse and also when the switch is closed. It's unswitched power so you do not need the key in the ignition to use the lights with the switch.

Very glad you got it to work, and maybe there's something different about the relay I used, but my wiring setup is exactly as I described it and you can follow the colors in the pictures.

The switch has power from the battery, to to the relay, and also a separate power supply for the illuminating LEDs that are hooked to the dimmer circuit. They light up regardless of whether or not the switch is on. Not all switches will have this.

jgohlke

The relay that I used has pin 30 and 87a connected when in the "off" state and 30 & 87 connected when "on". I wired hot from the battery to pin 87 and hot from the switch to 87a. Pin 30 went to the lights.

The switch turns them on anytime (key not required) and the reverse lights trigger the relay which connects 87/30, energizing the lights.

Mine works the same way you describe including the dimmer tap.

I'm not an electrical guy, but from the reading I did, I think all the automotive relays are the same and have the same pin outs. I'm guessing we have ours wired the same and you just wrote it down wrong. Unless your relay works differently, it won't work wired as you describe.

In your original post, pin 30 is connected to the pos on the battery and pin 87a goes through the switch and back to the pos on the battery. Obviously, that isn't going to work. The switch ends up with "hot"'on both sides. Since 30/87a are connected in the off state, this back-feeds power to the switch and lights it up (like it is turned on). Also because 87 is the only pin connected to the lights and it gets power from 30, but only when the relay is energized, the lights only come on when the truck is in reverse. If you study a schematic of the relay and look at your original post, you will see that it won't work.

In the end, I am grateful for the post. It was very helpful in showing me the way and I didn't know about the switches or that web page. I probably wouldn't have cut the dash without seeing your post and how well it came out. I am very happy with the outcome. It is my most professional mod!

Theocoog

I don't know a lot about wiring myself, but I think there's more than one way to wire a relay.

Here's what I had in my original post as far as wires going into the relay:

• Blue wire (relay Pin 30) – Connected directly to battery.
• Red wire (Pin 87) – Power from the relay to the Rigid lights.
• Black wire (Pin 86)- From the relay to ground.
• White wire (Pin 85) – Trigger wire that gets connected to reverse light circuit.
• Green wire (Pin 87a)– Trigger wire from switch in the cab.

And here is the circuit diagram I followed - I wish I could have posted this as part of my original post, but I didn't have a scanner then.


It works, just like in my original post. The only changes I made were:

1. I used Rigid lights instead of KC
2. I switched the green and blue wires since I had more blue wire
3. I used a Carling Contoura V switch that called for separate power and ground for the switch illumination LEDs. These are not shown on the diagram.

When the relay is at rest, pins 30 and 87A are connected. Provide power to 87A by turning the switch on and the lights go on:


When I shift into reverse and the switch is off, the white wire connected to pin 85 energizes the relay coil, and the lights go on:



Anyway, I'm glad your lights are working and that you found the post helpful!

benchwarmer4203

Okay, I did a little research so we could put this to bed. Your KC3300 relay does not have an 87a terminal. It actually has dual 87 terminals.



It's the first diagram of these three ^

Here's the wiring for that relay from KC's website:

http://support.kchilites.com/index.p...ch&attach_id=4

The second set of diagrams that you posted are from a different style of relay (not the one that you have installed.)

Okay, now...on to why yours works the way that it's currently wired. As you described, when you put the truck in reverse the coil in the relay is energized, the internal switch is closed, and pin 30 energizes the 87 pins. This turns on your lights and also back energizes your in cab switch through the center 87 pin. If your switch has an indicator light for when the lights are on it should illuminate that light while the truck is in reverse.

On to the point of confusion, the switch. When you close your in cab switch you are feeding your lights directly through it, so the relay does not limit the current that the switch is making and breaking. As long as your switch is rated to handle the current, this isn't a big deal. Your duallys draw 1.45 amps each for a total of 2.9 amps. From the looks of your switch, I would say it's rated for at least 20 amps.

The moral of the story here is you're using a 5 pin KC relay that has dual 87 terminals versus the other poster's Bosch style 5 pin relay which has a normally open 87 and a normally closed 87a contact.

Clear as mud, right?

jgohlke

Thanks Benchwarmer....I knew something was up! The dual 87 pins explain it. Seems like you know more than the two of us put together! Appreciate you helping out.

I think the KC relay with the dual 87 pins may be non-standard. All the ones I looked at online and locally had both 87 and 87a pin outs.

If anybody is following along at this point, the standard automotive 5-pin relay with pins 87 & 87a should be wired as follows:

Pin 87 – Connected directly to battery, protected by 15A fuse.
Pin 30 – New B/U Lights, positive wire
Pin 86 - ground (or neg terminal on battery)
Pin 85 – Original Truck B/U lights, positive wire
Pin 87a – Power wire from the switch in the cab

Theocoog

Thanks for clearing this up Benchwarmer. You're right that I'm using a KC3300 relay, which looks the same as a standard Bosch, but must have very different internals.

benchwarmer4203

No problem guys, and the good news is...you were both right!

mr7confused

Hey Thanks for the props!! Very well done write-up. Much better than I could do myself with my ADD haha

One thing I've noticed with having mine for the past couple years, is that sometimes when I shift into park, the quick pass by reverse might lock the relay on and I'll be walking away from my truck with them stuck on. A couple toggles of the switch and it fixes it no problem. Maybe it's just my relay, but it's something to be aware of.

If I were to do this again, I may run three wires up from the back so that I can have a "monitor" wire, leading directly from the lights to make sure I never left them on.

benchwarmer4203

Good observation...relays can definitely do that over time.

For the OPs configuration with the KC3300 relay, I believe that the indicator light on the switch is indeed energized when the truck is put in reverse and the switch is off. If the relay stuck, the indicator light would stay on while in park and alert him. Coog, would you be able to confirm or deny that the indicator light for your switch comes on when you shift into reverse?

Theocoog

Confirmed, and I like it! The indicator LED goes on if use the switch OR if I put it in reverse.

On a side note, I am swapping out my switch, which has blue LEDs, for one that has green/amber. The blue LEDs are super bright (even the illuminating LED) and I always think my brights are on. The OTRATTW owner bought an F-150 and is on this forum now, and he recommended the green/amber combination.