Dimming LED dash lights

Here is the problem. If you like me have "traditional" rheostat for dash lights dimmer you will not be able to dim your LED dash lights. It is easy to check if you have rheostat as it has 2-wires plug and looks like that.



It is just simple 0-10ohm variable resistor that is in series with all dash bulbs. The resistance is calculated for the dimmer to work correctly assuming all bulbs work (no burned bulbs) and all bulbs are the original incandescent type. Because LED bulbs take much less current then the given resistance will not dim them correctly. The worse case is when you have a mix of incandescent bulbs and LED bulbs. In that case when you try to dim dash lights, inscndescend bulbs will be dimmed a little and LED bulbs will shine full brightness all the scale (except when dimer position is on "OFF").

The proven and the easiest solution is replace the rheostat type 2-wire dimmer with electronic type 3-wire dimmer, used in most Toyota cars from years 1990-2005 (maybe more). Most of them are same and 100% compatible also mechanically with 1st gen Tacoma. I bought of ebay "92 93 94 95 96 TOYOTA PICKUP 4RUNNER INTERIOR DIMMER SWITCH BUTTON" that looks like that this one "92-02 Toyota 4Runner Light Dimmer Rheostat Switch OEM 84119-32090"



This is electronic 3-wire dimer with a bit different plug



Now for easy upgrade you need to get original pigtail for this dimmer. So if you grab it from a junk yard don't forget to get the plug. The one I bought of ebay came with 6inch long pigtail.

Now the easy part, you don't need to cut wires in your truck. Just disassembly the 2-wire plug for rheostat by removing both contacts from the plastic plug and put them in 3-wire plug. Color are matching too: white/black (ground) and white/green (from all dash bulbs). Now you need to add the third wire. It is +12V from your tail. You need to to splice any green/red wire in the dash: for example from radio, HVAC lighting panel, AC switch, basically any dimmable bulb. My truck does not have many of them, so the lowest hanging fruit was radio (my aftermarket deck does not use that wire anyway).

Electronic dimmer will fit right into place of a rheostat, even knob mounts the same (dimmer I bought had old washed-out knob) so you can reuse yours from rheostat.

By the way, replacing this dimmer can be done without removing upper dash panel - only lower part needs to be removed for the installation. If you have e-locker you can splice green/red wire from that switch (it is lighted dimmable) - it is next to dimmer.

Today I finally I had some time to do the swap and I could get rid of my rheostat conversion circuit I had for the last few years.

Here is the wiring diagram showing both dimmers options (obviously only one is connected).



And these are connectors for both dimmers



Alternatively if you don't have R3 connector you can disassembly R4 and after heat shrinking each contact plug each wire separately. That will work too. Just make sure to connect them correctly.

 

Great write up Rysuim. Some of the later Toyota's like my 04 has both plugs behind the dash. Why? who knows

 

Hello RysiuM,
I am wondering if this will work for me?
I have a 85 Toyota Ext Cab SR5 4WD.
Reading your Directions
As you can see from the Pics I have the white/black (ground)

I Dont have white/green(from all dash bulbs)..
I have a RED/BLACK wire?
I guess it would be the same just not 100% sure is why I ask..

For the third wire, Makes me wonder if my truck has green/red wire in the dash
I know my aftermarket Radio Doesnt DIM I had no IDEA that was an Option on the OEM Radio's?

Thank you
John

 

Hi John,

Without the Electrical Diagram of your truck I can't say which wire is doing what. If you truck has a rheostat plugged into this plug than most likely the conversion to 3-wire dimmer will work. You just need to find a 12V source that get's power when you turn on your dash lights. I think you can pull it from front or tail markers too. It may be a different fuse (or not) but should turn on with the same light selector switch.

Edit:

Looking on the Internet I just found interesting page: http://6thgeargarage.net/1985-toyota-pickup-truck-hilux-4runner-wiring-diagram/

The page showing illumination part agrees with your wire coloring: Red-Black is the same as White-Green on Tacoma, White-Black is the same as White-Black in Tacoma. As for the Green-red wire in Tacoma it is Green wire in your truck. You can pull it from many places in your truck besides any dash light (and clock if you have) also thing like tail lights, front marker (thy are called "Clearance" here), license plate light, even from what it is called here "Deck Light" - I only can guess that maybe it is a "cabin light". Basically anything that behind 15A Tail Fuse.

 

Hi RysiuM,
Thank you for getting back to me.
Im good following steep by steep instructions until it looks like my setup wont work.
I have no clue if my truck has a rheostat plug!?
I found this page for electrical I attached it. Chapter26to29 .pdf Page 25
And to figure out were to attach the 3rd wire should be No fun.
the Deck Light is the light in the bed of the truck

I wish I understood all this Stuff.. I have disabilities.
Sorry.
---------

I did an edit and added this part.
PS..
I think you are saying.

Is the rheostat the Spring Coil on the back side of the dimmer?
If Yes
Then I have the 2 prong rheostat dimmer. I looked behind it with a Mirror..

Now the easy part, you don't need to cut wires in your truck.
Just disassembly the 2-wire plug for rheostat by removing both contacts from the plastic plug and put them in 3-wire plug.
Color are matching too: white/black (ground)
and Red-Black (from all dash bulbs).
Now you need to add the third wire. It is +12V from your tail.
You need to to splice any Green wire in the dash:
for example from radio, HVAC lighting panel, AC switch, basically any dimmable bulb.

Your Note::
My truck does not have many of them, so the lowest hanging fruit was radio (my aftermarket deck does not use that wire anyway).

I could do the Radio Also?

So the R3 Connector should look like this?
#1 Ground white/black
#2 Positive Red-Black
#3 Green wire.

Thank you.

 

Based on colors mapping this is how you should connect electronic dimmer to 85 Pickup



Green wire can be obtained from ant of the following sources or near by (if you have that option installed):

1 Deck light switch
2 Clinometer & Altimeter backlight
3 Heater Control backlight
4 A/T Indicator backlight
5 O/D switch backlight
6 Radio
7 Combination Meter backlight
8 Defogger Switch backlight
9 Cruise Control Switch backlight
10 Clock
11 Front and Rear Markers
12 Fuse 15A Tail (green wire side)

 

Sorry RysiuM,
I dont know how to read this diagram! (the first picture I attached)
And I am not 100% sure..

So Instead of how you show R3 wired up you have it 1,2, and 3 (Pic Attached)
Are you saying I want
#1 Green wire.
#2 Ground white/black
#3 Positive Red-Black
----
I understand all the Green Wire Options.
Thank you very cool green marked diagram.
I just have No Clue Were To Look For Them on the Truck?


Thank you

 

No Godly idea what we're talking about here.

 

Yes, the picture if the plug is correct.

As where to look for that green wire you need identify what equipment of listed you have. Locate these switches and other eqipment (radio, clock etc) and decide which one is the lowest hanging fruit (eady yo access and clise to the rheostat. On the plug to that swich or equipment look for a gren wire an splice it. On these plugs there will be only one green wire so it is easy to identify.

 

Hey RysiuM,
Thank you Thank you
For all your help and time.
This is awesome.
I like you found a 3 prong dimer and plug on ebay it cost me with shipping and tax $27.64

I will get that Green wire location figured out, I just want it to be as short as possible..
I know the Green is the PWM of the dimmer..

Here is a Copy of My Version of Directions for Older Trucks.
I did use some of your Pictures I hope is ok?!

Again
Thank you

 

Hey RysiuM,
Just curious did you see the write up I did
Its attached to my last post.

Thank you so much again,
John

 

I got a 3 pin connector off of a 94 4runner. Pins 2 & 3 are W-B and W-G respectively; however, pin 1 wire is colored green with white dots.

Thank you very much! Genius!

 

Great upgrade idea...! Does this 3-pin electronic rheostat tolerate a mixture of incandescent and LED illumination bulbs, or even all-incandescent (curiosity only about this) bulbs? Or must it be all LED bulbs, otherwise it'll burn out with the much (could be 5-10x?) higher current?

 

Sorry for the late response - all looks good. Thank you for putting it all together.

 

3-pin electronic dimmer doesn't care what bulbs you use (can be all incandescent, incandescent and Led mix or all LED). BUT: there is a limitation what kind of LED bulb you use. They must be "dimmable". Som LED bulbs have built in fancy "buck driver" that keeps brightness at the same level regardless of the voltage powering it (these bulbs are often advertised or describes as 12-24V) - they are not good. They will not dim but either flicker or just cut of. What you need is the cheap and simple LET that are designed for 12V and they are polarity sensitive (they usually have just one diode and one resistor for the current limiting).

 

Nice surprise you're answering after 1.5 years, thanks.

That's a problem I've had from the beginning--12v dimmable automotive interior illumination LED lights are very hard to find. I haven't found any. I think 'LET' was meant to be LED...?

So, to confirm, an LED bulb like this https://www.superbrightleds.com/veh...it-car-194-x5-car+volts-9-145~VDC+color-Green will dim much like an incandescent bulb--right down to very dim? Most of my long-distance driving is done at night and I really like my dash lights very dim--to the point that I've kept using incandescent bulbs, as LED bulbs are too bright...

 

It is not that I was ignoring you, just have not been accessing Tacomaworld for a while.

To my best guess it looks like they did not pack that bulb with a lot of electronics, so probably it is the kind that will work. There is another "catch" in LED bulbs, that nobody is publishing so you need to take a chance, buy it and check for yourself. It is the "cut-off" voltage - the lowest voltage the bulb will turn on. The simplest LED bulb internal diagram is:



LED chips and diode in series have a static voltage drop (simplified). So the current will not flow if the voltage supplied is below that voltage. So below that voltage LED bulb will be dark. The trick is that if not all bulbs in the dash, that controlled by the dimmer have the same voltage drop, then bulbs with the highest voltage drop will go out before these with the lower voltage drop.
The dimmer itself also has a minimum voltage supplied before it cuts of the power (the voltage at the minimum brightness set). I did not measure the minimum voltage coming out from the electronic dimmer before the dimmer cuts off, but to not have a "Christmas tree" effect all bulbs controlled by the dimmer should have the cut-off voltage lower than the dimmer cut-off voltage.

This is how you can turn a simple dash lights dimming into a rocket science .