Convert headlight switch cluster to LED

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
My conversion was performed with 18,000mcd white LED's. Because these are way too bright for nighttime use, I used a larger-than-normal resistor to bring the brightness down to match the intensity of the original bulbs. Your resistor value will vary depending on the particular LED and color that you use. I suggest using one of the various online resistor calculators to choose your starting resistor, then go to larger values of resistance to make your LED dimmer.

To begin disassembly, pop out the dimmer switch, then pull the knob straight off. Underneath you will find a shaft with a nut at the bottom. Using a thin-walled socket or some long,thin needle-nose plier, unscrew this nut.
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Around the sides of the housing you will find four tabs. Using a small flat screwdriver, pop each tab loose until the case comes apart. With the light buttons facing down, pull the back of the housing straight up and off. These are the pieces you will end up with. You will note that your circuit board already uses LEDs for the indicators, but is using light bulbs for the general backlighting.
img_6426x.jpg


To reduce the voltage to your new LEDs, we need to modify the circuit traces and insert resistors of the correct value. Using a dremmel, cut the traces in the two circled locations. If you do not have factory fog lights, you probably do not have a light in the location on the right. In this case, disregard cutting this trace or adding the subsequent LED and resistor.
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One final trace needs cut on the front side in the circled location. Sand the lens of each LED with some 200-400 grit sandpaper to give them a frosted look. This will help spread out the light more evenly behind the switch. Remove each light bulb, and solder your LEDs in place, noting the location of the positive (longer) lead as marked on the picture. If you are using T5 LEDs, you can set them down flat to the circuit board when you solder them in place.
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To bridge the gap you cut in the trace (just below the red switch), use a small knife to scrape back the green coating over the traces. Be careful not to scrape away the copper underneath! You can solder the legs of the resistor directly to the exposed copper.
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On the back side, one leg of each resistor will be soldered to the LED, and the other leg of the resistor will be soldered to a circuit trace. Again, carefully scrape the green coating back to expose the copper.
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Once you have finished soldering, you can (carefully!) plug the bare board into the wiring harness in your vehicle, making certain you have each plug turned the right direction. Failure to get this right can cause permanent damage to your light switch. If in doubt, lay the circuit board into the back of the housing so you can see the proper orientation of both connectors.

Watch the LED's closely as you turn the key to ignition. If you see an LED flash brightly then go out, it got too much voltage. Verify that you cut the proper circuit board traces, and measure your resistor values. If you put a voltmeter across the legs of the now-dead LED, you should only see about 2.6 volts.

If an LED does not light up, but did not flash when it first got power, you may have soldered it in with the wrong polarity. Remove the LED and solder it in the right direction. Also confirm that the resistors are soldered to the right locations.

To finish, you should clean the solder flux off the circuit board. Wash the board under water and use an old toothbrush to lightly scrub the areas you soldered. If the water does not remove the flux, use alcohol to remove the rest, then wash in water again. Try not to disturb the grease around the headlight contact points on the board. Dry the board completely before reassembly.

One issue I had with putting the housing back together was the spring for the interior lamp switch. Set the circuit board into the back of the housing, placing the dimmer switch in its keyed slot. Assemble the interior switch components, noting that the red spring needs to go around the outside of the tab at the top of the black rectangular sleeve. If you do not get this spring in the right location, after assembling the housing you will find that pressing the black interior light button does not come in contact with the red switch, and does not smoothly push in. Make sure and check the operation of this switch before putting the dimmer nut back on.
img_6432x.jpg


The last step is putting the dimmer nut back in. This is a tricky process unless you happen to have some kind of specialty tool for it. Between using a small flat screwdriver and my needle-nose pliers, I was finally able to get the nut threaded back on and screwed down tight. Press the knob back onto the shaft (it only goes on one way) and check that the knob can be rotated and pushed in and out. Reassemble the switch housing back into your vehicle.
 
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Blckshdw

Moderator
Nov 20, 2011
10,697
Tampa Bay Area, FL
:undecided: Cutting the traces and putting the resistors on the backside of the board. Didn't think of that. Nice write up though.
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
smitty5150 said:
I just wired my resistor inline with the lamp. This might be worth a rewire.

That's how I did the LEDs in my climate control. It's functional, but I think this method leaves the new components a lot more solid.
 

Blckshdw

Moderator
Nov 20, 2011
10,697
Tampa Bay Area, FL
What are the clear factory bulbs? Mine has two (one broken and one blown). Is there a part number for them?

There isn't a part number, but you can replace them with any similar sized 12v bulb. If you're overly concerned with uniform brightness, you could replace each of the bulbs with new ones, since you're going to have the circuit board out anyway, and it would be annoying to complete the swap, then one of the other bulbs blows. Not to mention if you order them online, they'll likely come in a pack of multiple bulbs, so they'll be on hand. :twocents:
 
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