Circuit and wiring gurus I need your help
 

I installed a gauge cluster with an LED backlighting system. The only downsides is that there is an external on/off switch,a dn I want it to turn on and off with the headlight switch.

The on/off switch is a paper thin piece of plastic with a very thin spongy button that sort of pops in and then out when released. This goes to some sort of relay. Black box in picture below.

Attachment 189544

I have the hot wire hooked into the headlight switch power, so there is no way to activate the LED lights unless the headlights are on. I turn the headlights on, then press the pwr button for the LED lights and they come on. When on turn the headlights off, everything turns off because all power is cut (yay). I tried removing the on off switch and bridging the terminals and turning the power on; nothing happens, If I undo the bridge and make contact they turn on, touch the terminals again, and they turn off.

Does it sound like there is a way to get this circuit to turn on and off with headlight switch?

For your viewing pleasure:

Attachment 189545

Can you give us a link to the documentation for this kit? The easiest thing would be to figure out what voltage it's outputting to drive the LEDs, and then eliminate the black box and replace it with a constant-on regulator supplied by the general illumination circuit.

No documentation, bought it off here a week ago from someone that got it with a car. I could just put a voltmeter on it. I can get the voltage that is immediately coming out of the box. Then is it a matter of creating something that steps down the voltage from 12 to whatever the box outputs? What data would you need? current, voltage???

Voltage across the wires going to the LEDs will probably suffice. If you have the ability to take an inline current measurement, all the better.

For the current reading to I just need to measure the current between the two pins before they reach the first LED? One wire out of the black box feeds all the LEDs

If you try to measure current by bridging across the two wires coming out of the controller, you will short circuit it. Current readings must always be taken in series, by interrupting the circuit and placing the meter inline with it.

Voltage readings, by comparison, are taken across the circuit (in parallel with it.) I'm more interested in voltage here, current would be more of a curiosity.

And yes, both of these can be done directly at the controller, or anywhere along the cable between it and the LEDs. You needn't touch the instrument cluster itself.

I'll get it as soon as I can. Working today.