LED Dimmer Switch

[BlackTomC]

Quick question for you electrical people.

I replaced all the bulbs behind the gauge cluster in my 76' GMC Suburban with some incredible looking LED's. Now that the transfer has been made, I can only turn them on or off with the existing (factory) dimmer switch vs before I could twist the knob, and dim them.

Question is, why is this happening? And is there a way I can alter the circuit to make them "dimmable" again?

[Irish_Alley]

afaik the leds have to have the dinner function. the ones you installed sound like they dont.

[BlackTomC]

What do you think about this

http://www.edn.com/design/power-management/4430321/How-to-make-LED-bulbs-dimmable
http://www.digikey.com/en/articles/techzone/2010/apr/how-to-dim-an-led

[BlackTomC]

From my understanding, dimming functionality in LED's comes from the switch/device that is providing power to them, not the actual LED.

[Irish_Alley]

i know we have members who have leds and theyre dimmable idk how or why

[Irish_Alley]

found it
http://forum.73-87chevytrucks.com/smforum/index.php?topic=27411.msg228068#msg228068

[BBM3]

This will allow you to use the factory dimmer.

Auto-Meter 9114

Install Instructions

[BlackTomC]

Found it, in order to achieve dimming with LED's you need to have a voltage dimmer, vs the old school way (I dont know how it used to be done).

[sphinx]

LEDs are current controlled devices.  You have to have a "driver" to limit the current while chopping the voltage into small pulses to trick your eyes onto thinking they are dimmer when they are actually only on for part of the time.  Have you ever noticed, especially on Cadillacs, that the LED tail lights appear to be flickering real fast, then when the breaks are applied the flicker is not as noticeable but the lights are brighter?  There are several dimmer circuits for controlling LEDs on 12 to 15 volts, this is what you need.  I'm sure ebay and Amazon should have some available.

[a.graham52]

 weird, the leds I put in my 85 dimmed with the factory switch. The leds under the dash in my gf's 98 also dim with the factory light switch. Odd

[BlackTomC]

A.Graham52,

You one lucky dude, I'd love to have dimming functionality with the original switch. I've gone through and replaced each dash cluster bulb with:

https://www.superbrightleds.com/moreinfo/miniature-wedge-base/194-can-bus-led-bulb-5-smd-led-wedge-base-tower/1127/

The LED's look great so far. I planned on redoing the headliner/painting the interior trim soon and was going to throw in a couple extra dome lights (LED of course), just sucks I can't get dimming functionality (or don't know how without hooking up aftermarket gear).

If anyone has suggestions, let me know.