Tapping the Dash Lights Circuit

Bringing back a thread from the dead.
Wiring the same CH4x4 switches, looking to pull illumination (+) off the green cargo light wire... but I'm not clear on the ground in this diagram.

Is this to ground the switch signal wire going to the accessory relay (I.e. chassis / bus ground)? Or illumination ground (I.e. tan illumination (-) wire on cargo light).

I assumed this circuit would take constant 12v from the desired power source, and illumination (+) wire would just provide the delta voltage for illumination and dimming.


Edit:
https://www.tacomaworld.com/threads/ch4x4-switches-to-dim.691662/

I suppose I just had to run inside, grab a beer and look at a computer screen.
It's answered in this thread and the link above. The ground according to the diagram just wasn't clear to me (Wire #4). Makes sense looking back at the RTMR and rest of the circuit.

 

Working on a little project. Using Molex connectors, and in the dash harness I made, I allowed for a ground wire to go with the rest of the loom to the fuse panel under the hood, a switch 12v wire to source (add a fuse under the hood), as well as two wires to tap under the dash - one for Illumination (+) and one for Illumination (-). Wires are all there, I just need to determine how I am grounding my switches for illumination control. To the chassis ground bus, or to the illumumination (-) via cargo light. (Thank you to the DIY RTMR build thread on TW).

Before:


After:

 

That black wire is ground for the leds only. It grounds both the illumination led that gets power from illumination positive(Red2)and the switch “on” led that gets power from the switch output(Red 1). But it doesn’t have any direct function with the switch itself. The switch only makes the connection between Green and Red1. Illumination positive is fixed, it’s the ground wire voltage that varies on our trucks.

 

anyone here have a pin-out diagram for the two connectors at the back of the cluster gauge?

 

be aware that some automotive branded switches (Amazon cheapie switches...i'm looking at you) use a common ground for the switch light and the switch pole or relay out, if you connect these to your dash dimmer line, you may find other switches lighting up, looking brighter than expected or other malfunctions. "good" switches will allow for different voltages at the switch and illumination leads. if you test for a continuity between the relay - and light - when either the switch is off or on and see a short, its one of those cheapie switches.

 

I bought my truck used, with no mods to the interior, but after buying it I notice the dash and stereo illumination goes bright then dull, over and over again..all of the time..day or night, going over bumps and sitting still...this post may help me figure out that issue..thanks for bringing this up

 

Might be the issue, might not. I've been using the 5A Panel fuse for over 3 years and has worked fine for illuminating an aftermarket switch. I have been using different harnesses now for lighting up switches when parking lights activated