JK-Ford

You don't understand the concept of the interposeing relays.

JK-Ford

The purpose of the interposeing relays is to isolate the aftermarket system from the OE system. The diode protects the OE circuit from the emf from the collapsing relay coil. It isn't designed to protect from back feeding the circuit like a fuse.

bobholthaus

Please explain. And on your setup, your diode is in the wrong place. When power flows through your relay #2, the power at 86 never gets anywhere near the power flowing through the relay at 30 and 87 (86 throws a magnet connecting 30 and 87, but that connected circuit never touches the power at 86). So your diode should be between 30 on relay 2 and the wiring to 30 on relay 1. When you have your switch on and the oe circuit activates, you are creating a wiring circle that shouldn't happen. Since its only flowing back through the same wire, it isn't causing a problem. But in your setup, with the way a relay works, power NEVER flows out of the relay back into 86, so there is absolutely no need for that diode.

Again, look at the lines I scratched on your drawing. Seriously, you are way over complicating this. Look at the way the factory wiring comes from Rigid Industries. With a diode on the oe circuit, you don't need a second relay. This is how guys are tapping their dome lights to power rock lights as well. The diode prevents the back flow of juice. You could have 5 switches running to the main 86 on relay 1, and as long as they all had an inline diode between the switch and 86, you would still only need one relay.

bobholthaus

Emf from a collapsing relay coil? I've been doing this 25 years and have never heard that term. I'm a member of probably 15 forums and my specialty is wiring. A diode's job in any circuit is to prevent the back flow of juice. A fuse's job in any circuit is to prevent a surge of power or an arc of power from melting a wire and starting a fire. Please keep explaining if I'm wrong here, but 25 years of experience in doing this has taught me a thing or two.

bobholthaus

Holy cow, I just googled that and was reading about Lenz' Law and Faradays Law of Induction. Crazy stuff. You're taking simple relay wiring to PhD level. Maybe by the laws of Lenz, Faraday and possibly Ohms, I'm wrong, but in the simple act of wiring a 12v relay for automotive use, I've never seen anyone ever mention the need for a diode on circuit 86 unless there were two sources of power running to that feed. And honestly, if you poll 99 out of 100 guys on this or most "common man" (non electric engineers) forums, most would agree that one relay is totally sufficient.

bbrown626

I ran my power wire through the hole in the firewall on the passenger side. Follow the factory wiring along the seats/doors under the trim. Run it back to the passenger side backup light. In there the relay with a diode is tied to the stock backup light. the power wire travels out the bottom of the tub and to my lights in the bumper. I don't use a switch so the lights in the bumper come on whenever the factory lights come on. Very simple setup.

Others have even wire directly to the factory wiring without running a separate line back from the battery. Recall that the system is designed to support the lights on a trailer. Your LED's will not be a problem. I have 55W halogens so I went with the relay and added line.

JK-Ford

For older vehicles, this is probably correct. But remember, these Jeeps have control systems almost like a computer. Not just simple relay logic.

OK, I've had time to sleep on this ( or not sleep ). So let me try to explain. Remember, the goal here is to have as little impact on the OE electrical systems. ( The OE systems are controled by a Computer ). And this type of control schem ( Relay Logic ) has been around for a lot longer than I. As was mentioned, the interposing relay logic has many different uses. It's used to control 1 device by 2 different voltages. It's used in "intrinsically safe" conditions where you need to control devices in a dangerous atmosphere. And, for this purpose, it's used to isolate sensitive control systems from more robust control systems.

Now that is cleared up. Don't confuse the primary system with the control system. They are to completely different systems. The primary system is simple and robust. Just straight power from the battery or what ever source. Through the relay contact. And Out to the load ( Lights ). This system has no contact or any bearing on the control system. It could be of any voltage or of any size. It's only relationship between the two relays is that they are both controling the same device. In my 30 years of service, I've never seen a primary system fail where it came in contact with the control system.

Now on to the good stuff. The two relays are for two control systems. The manual ( robust ) control system. And the second, the sensitive control system. The manual system is just straight forward aftermarket style. A simple switch and a simple relay. The sensitive control system just simply "piggybacks" onto the robust system. It does the same thing as the robust system. But it also isolates the sensitive control system from the robust control system. The design itself is the primary protection for the control system. The components ( Fuse and Diode ) are considered back-up protection for the sensitive system.

The drawing I provided ( the one that was altered by Bob ) shows the diode preventing a backfeed from the robust control system. Yes this system works. But this system uses the diode as a primary means to protect from back-feeding the sensitive control system. Just think about what would happen if this system were to fail. Do you seriously want a $0.50 component protecting the electrical systems of your Jeep.

Now look at the orignal drawing. This system uses the diode as a secondary means of protecting the Jeep systems. The primary protection is in the design itself. If this system fails, the only loss is the automatic control of some silly little lights. And If the diode were to fail, it may allow an emf flux from the relay coil onto the control tap. But that flux may be interupted by the in-line fuse on that same circuit. NO RISK to the OE systems. This system is commonly deployed to protect advanced /sensitive control devices ( Jeep Computer ). This system is in-use at the industrial facility where I work protecting the PLC Control Systems. You can purchase automotive relays with the diode "built-in".

Bottom Line This is YOUR Jeep we are talking about. You may consider this theory to be to advanced for such simple lighting control. But remember, our Jeeps are a lot more advanced than previous models. How well do you want to protect your investment?

fanatic

Wow! This discussion has gone way to advanced for me. I'm gonna wire straight to the battery to avoid the factory stuff. I don't want these coming on with the reverse lights, they will be too bright. Although I appreciate the advanced electrical class we are having, we have almost avoided the question of "what's the best way to get from outside the jeep to inside, not using the hole in the tailgate".

JK-Ford

OK, thought we already took care of that. Sorry. I was just trying to make recommendations on improving your system.

fanatic

I appreciate all the input on wiring. I'm the furthest thing from an electrician, so I was just going to wire straight to the battery with the provided harness ( lengthening where needed) to avoid issues with the can-bus. I only want it to work off the switch so this should be fine right?