'14 Trail
I tapped into the green and grey wires on my OEM heated windshield washer button to use the dimming on another switch. I used a multimeter to test and measure the voltage as I rotated the dimmer switch and it appeared to work as the voltage went down and up as I moved the dimming wheel respectively.

Then because I'm an idiot... I moved the probe connector to the DC10A spot on the bottom left of the multimeter (image attached) thinking oh, vehicle is DC due to battery. Now I get no light at all on my OEM heated windshield washer button dimmed or fully bright and no reading on the tap leads as I measured before being stupid. Did I just blow the light on the OEM switch or did I screw up something else worse? The console (speedo etc.) still dim when I move the wheel.

I just bought another OEM heated windshield switch off of eBay... hopefully I get the dimmable light back with it!

Did you check the fuse?

I looked to see if there is a fuse for switch dimming but didn't see/find it. Which fuse should I be looking at?

I’m not sure. Maybe someone else will chime in. This is the first car I’ve seen with these dinky fuses. I don’t know if it’s possible to tell if they’re blown just by looking.

The DC10A input is for measuring current (amperes) up to 10 amps. It is a dead short across the leads. Thus, if you are lucky, the fuse if blown. If not lucky, you may have melted wires in the wire harness.

I didn't smell anything burnt or melted, so fingers crossed there. I'm not sure which fuse to check. I don't see one for light dimming. Can you tell me which fuse I would check for the dimmable switch/button lights?

Here is a diagram reference for the fuses:
https://fuse-box.info/toyota/toyota-...010-2017-fuses

The switch still functions, just not the dimmable light on it. All other dimmable lights, instrument panel, traction control knob/button lights, still function as they should (their blue light comes on and dims properly). Just the one switch that I tapped and tried to meter had the blue illumination dimmable light go dead.

I'm hoping I just blew out the LED light on the switch. Will have to see when I get the switch I bought off of eBay...

If the lights on all the other switches come on with the headlights except that one, then it’s probably the switch and not the fuse.

Is there a pdf electrical diagram available for these cars?

Replaced the switch with the one I got off of eBay and same problem, dim light on switch is dead... So I either blew something, or melted the wire within the harness :-( Maybe the tap I did broke the connection and it's just coincidence that it happened when I did the multimeter stupid above?

Finally got some time to check fuses. It was the #2 Panel fuse in the box under the driver-side dash... At least it's all working now :-)

Glad it worked out.