Dimming aftermarket gauges.

[sirdan]

This is a question for my 1988 4 runner but I am betting the celica operates the same way and maybe you guys can help.  I have an aftermarket gauge pillar and I hooked the lights up to the old radio illumination wire (I think). Lights turn on and off but now dimming with the dimmer switch.  Anyway I decided id look at the wire going to the console lights as it is easy to get to and those lights also dim. I probed the wire with the multimeter and if I moved the dimmer switch I would get different voltages. Before I bothered trying to wire up to that plug I got out the test light and probed the wire but when I turned the dimmer it did not change the test lights brightness. What gives?

I looked at maybe testing at the switch but its pretty buried under the dash. Any thoughts on this? If its going to be a huge pain in the ass I might just dim them down where I want them with a resistor and put an on/off switch in for them. Kind of blinding at night right now.

[RedCar]

If your test light isn't incandescent like the dash bulbs, then all bets are off...  unlike incandescent, i think a lot of LED devices have a pretty narrow voltage range that could cause them to change brightness and otherwise they're just on or off.

I don't know that much about after market gauges... but my afr gauge dimmer wire just connected to the headlight wire and used that signal to tell it's little internal brain to turn down the illumination.

[sirdan]

The gauges aren't LED they are just incandescent just like the test light.

[ozzie]

The radio illumination wire may simply not be dimmed. Keep in mind that the potentiometer dimming your stock gauges could be either on the power supply or ground side of the circuit. Check the wiring diagram in the back of the Haynes manual, or the FSM/ESM if you have access to it.

[sirdan]

https://i.imgur.com/n38wZ9j.jpg

looks like it works off the ground.  I could have swore I probed both the radio wires leftover and the console wire grounds and nothing changed with the dimmer.

[RedCar]

One confusing thing I recall: It seemed like some of those wires in the radio area are just floating unless the the relay from key being in on position is active. Maybe you already tried it this way... but it might be worth it to do the test with key in on position, and headlights on just to make sure the relays are in proper position?