Need some help please. Picked up a bumper with 40 LEDs and the installer said the switch wasn't powering correctly. Then my local Jeep shop said that even with an additional relay (switched by fog light switch) the lights would turn on, flash a few times then off.
All this evidence (and forum searching) leads me to think that this is a CANBUS system, the LED is returning a different load than expected, powers off thusly, and that I'll need a new switch.
Am I unthinking this? Can I get the stock switch to work?
The power for your LEDs should be coming directly from your battery to ensure you aren't messing with any other systems. If you run a properly fused wire from the battery to the original switch and then to the LEDs, there should be no issue. If you want to operate the LEDs off the fog light switch, you should be able to make that work as well, but again, you supply power should come directly from the battery to the relay. Do you know where they tapped in to power the LEDs?
The problem is trying to use the factory fog switch. These are not regular switches that most of us are use to. New vehicles use a can bus system to operate the vehicle functions. Think of it as a network, for example in the steering column instead of individual wires running from each switch to the intended function (horn, fog lights, turn signal, etc) the controls are connected to the body computer. When you press the horn it sends a message to the computer saying "I want to honk" then the computer activates the relay for the horn.
It's obviously more complicated than this but this type of system uses less wiring and allows easier configuration of the vehicle.
So to answer your question, for your lights you will need to install an aftermarket switch bypassing the can bus system.
If you are going to install more aftermarket electrical items I would look into the spod system.
Keep in mind that with the low voltage cutoff, if your battery is on its last leg, it may drain it below the battery's ability to start the motor. Additionally, if you routinely drain the battery down to the point of the low voltage cutoff, it will significantly shorten the life of your battery.