Convert rear wiper switch 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.

The switch disassembled. There are two tabs, one on either side of the case, that need to be pushed in and towards the back of the switch in order to pop the case apart. To reassemble, just snap the pieces back together.
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Measure the height of the original bulbs. After you remove them, you want to set the new LEDs to the same height. The picture shows a '+' mark for the positive side (longer lead) of each LED. To remove the LEDs from the 12V power source, use a dremmel to remove the circled traces from the circuit board. Three traces come together at this point - make sure all connectivity between all three has been removed.
img_6411x.jpg


The back side of the circuit board, showing the placement of the resistors. Because of its location, the LED for the center washer button appeared brighter than the dial. In my case, I used 5.1K resistors for the outer LEDs, and a 5.6K resistor for the center button LED. Exact values are not critical, and you can freely use 1% and 5% resistors as available. Note the X showing the location of a trace underneath the resistor that must also be cut. The bottom leg of this resistor is soldered to the circuit trace underneath it. It is NOT connected to the left-hand pin of the connector. The bottom-right resistor is connected to the negative leg of the LED, and to the connector pin that is second from the right. Ensure that this legs of the resistor does not come in contact with the circuit traces that are running underneath it.
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Use a soldering iron with a narrow tip. Too much heat can damage the circuit board. Liquid solder flux can help greatly in getting a good connection between the resistor legs and the circuit board traces. Once you have finished soldering, you can (carefully!) plug the bare board into the wiring harness in your vehicle, making certain you have it turned the right direction. Failure to get this right can cause permanent damage to your wiper controller.

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.

Once you have all three LEDs lit up, place the front of the switch over the top of the circuit board and observe how they look. If you have noticeable bright spots, sand the lens of the LEDs with some 200-400 grit sandpaper to give them a frosted look. You may also wish to bend the outer two LEDs over slightly so they are not aimed directly at your switch face. With a little work, you can get the LED's to provide a uniform glow to all of the indicators on the switch face.

Once you are satisfied, you need to clean the solder flux off the circuit board. Wash the whole 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. Dry the board completely before reassembling the switch.
 

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