dim led on switch

Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=125649
Printed Date: May 05, 2025 at 4:18 AM

Topic: dim led on switch

Posted By: cmorales
Subject: dim led on switch
Date Posted: January 13, 2011 at 11:26 AM

Hi...
I want to have a switch illuminate very dim always and increase intensity when the light switch is turned on. Will this work? adding two blocking diodes and extra resistor (in red) to the current wiring?

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Replies:

Posted By: oldspark
Date Posted: January 13, 2011 at 11:56 AM

Why not have one resistor across the switch (in-out).
Then when the switch is closed, it shorts out that resistor leaving only the other.

The LED will always be lit though - unless in your diagram, the +12V is IGN or ACC +12V.

But it should work, but you'll have to experiment with the resistor values.

Posted By: cmorales
Date Posted: January 13, 2011 at 12:25 PM

Thanks oldspark.

I want to always be lit, just dimmer. And when turning on the car lights i want the switch indicator to increase intensity.

Posted By: oldspark
Date Posted: January 13, 2011 at 3:29 PM

Ok. It's as I said - the +12V batter resistor between the switch +12V input and the tail-light terminal, and from there to the LED & resistor.

The "+12V interior illumination" on you diagram is therefore the tail-light terminal.
Or the beam terminal if you don't want it brighter for parkers.

You could have problems if there are other LEDs on relays on those circuits - ie, the resistor/s may be comparable to relay coil resistance etc - hence setting up a voltage divider. But if any such relays do not stay on with the switch off, then no problem.

And I said tail-light in case it's an older vehicle where front parkets are not lit with the main beams.