This tutorial is very long and extremely in-depth. I typed this to help anybody with very little electronics background understand what he or she is doing and how to do it. I probably left out a lot of information but will try to edit the post as much as possible to be as user-friendly and as accurate as possible.
First, let me start off with a quick disclaimer:
The following is a tutorial on how to replace the factory surface mount diode LED’s in a window switch pack. It is not recommended that you attempt this unless you have sufficient knowledge of electronics. The job will require multiple calculations, calculations which can cause electrical failure or worse, an electrical fire if not done correctly.
I am posting this tutorial for educational purposes and cannot be held liable for any damage to your vehicle resulting from this tutorial. The following information is given to you at the best of my ability and if used correctly, will result in a successful light emitting diode swap. The following tutorial is based on the circuitry for a 2003 Nissan Pathfinder and may differ slightly for other vehicles.
If you need help with any parts suggestions or calculations, please feel free to post on this thread and hopefully someone will promptly help you.
Now, on to the materials and tools needed for this job.
MATERIALS:--------------------• SolderFor this job I used 60/40 Rosin-Core, 0.05 diameter. A smaller diameter solder will make it easier to work in tight areas. This can be purchased at a Radio Shack or somewhere similar.
• Resistors The number of resistors needed will depend on how many SMD LED’s you will be replacing; I used 1/2 watt carbon-film resistors with 5% tolerance. You may be able to use 1/4 watt resistors, but you should not use more than 60% of the resistors power rating (Power = (V * V)/R, where V is measured voltage value [usually 12-14V] and R is the resistance value of said resistor). I recommend using 1/2 watt just to play it safe. These can be purchased at a Radio Shack or somewhere similar.
• LED’sThe number of LED’s needed will depend on how many SMD LED’s you will be replacing. You can use a 5mm or 3mm through-hole LED, no larger. You can also use SMD LED’s but they are much more difficult to solder and this tutorial will only work with through-hole LED’s. I used a white 5mm through-hole LED. This can be purchased at a Radio Shack or somewhere similar, I purchased mine from SuperBrightLEDs.com.
Picture 1 (Just some of the materials used for the job)
• Soldering IronMost soldering irons will work; I used a high heat iron. Make sure you have a pencil-tip on the iron.
• Digital MultimeterThis is absolutely necessary for the job. Preferably you want one that can measure voltage and resistance. One that can check for continuity and measure diode characteristics is a huge plus. These can be purchase at most hardware stores; a brand I highly recommend is Fluke, they make some of the best.
• Mini Screwdriver SetThese are not completely necessary, but they make disassembly much easier. The flat head screwdrivers will be used to pry open parts and such.
• Standard sized screwdriver setThese will be used for disassembly
• Point-Nosed Mini Pliers (or something similar)These will be used to pull the factory SMD LED’s off the board. The miniature kind is best, but a large pair of needle-nose pliers may work
• Xacto KnifeThis will be used to cut and peel away the board trace. These are fairly crucial, as a standard straight blade won’t work.
• TweezersThe more accurate the better, you want the pointiest end possible. These will be used to pull the factory SMD LED’s terminals from the solder.
Picture 2 (My collection of tools for this job)
Now let’s begin!
STEP 1:--------------------First we must pull the switch pack off the door. Grab a standard sized flat-head screwdriver and a mini flat-head screwdriver and go out to the car. It is not necessary to pull the negative cable from the car battery, we will need the battery connected to measure some voltages in later steps.
STEP 2:--------------------We begin by prying up the switch pack from the door, the easiest way would be using your hands and pulling up at the lip where the armrest meets the switch pack trim. If you can’t pull it up using your hand, try using the standard sized flathead screwdriver to pry up the trim. If you don’t have enough space for the large screwdriver to pry it off, use the mini screwdriver to get some space and then slide the larger screwdriver in to pry it off. You can see in the second picture where the clips are. It is best if you position your screwdriver right next to the clip as the plastic pieces on the switch panel can break very easily. Once you have it pulled off, you want to disconnect the wiring harnesses, this can be done by just using the standard sized screwdriver and pressing in the tabs and pulling the switch pack to free the harnesses.
The service manuals recommended removal procedure
Picture 3 (You can see the clips which hold the trim onto the door)
Picture 4 (Pushing in harness tab to remove harness)
Picture 5 (Pushing in harness tab to remove harness)
STEP 3:--------------------Now we need to remove the actual switch pack from the trim panel, you can do so by removing the three screws which hold it in place. Now you can just pull the switch pack from the trim. Now we need to pull the buttons and cover off of the base of the switch pack. To do this, you want to pry the sides open and pull the base out completely. The easiest way is to use the mini screwdrivers to hold the sides open and then pull out the base.
Picture 6 (The three screws to remove the switch pack are circled in red)
Picture 7 (Switch pack removed from trim)
Picture 8 (Using mini screwdrivers to pry sides outward)
Picture 9 (Pulling off switches from switch pack base)
Picture 10 (Switch pack base pulled out of switches)
STEP 4:--------------------Now we can see all of the circuitry from the switch pack. Now we need to go back out to the car with the switch pack base (circuit) and the digital multimeter. We need to measure the voltage across each LED. To do this you want to attach your black multimeter lead to some bare metal under the drivers knee trim panel. Position it so it stays attached to the metal so you don’t have to hold it. Now you want to measure the voltage being fed to the LED’s. You want to plug the switch pack back into the door and start the car. You will see the factory SMD LED’s light up.
Now to want to take the red lead for the multimeter and touch it to one side (soldered terminal) of an SMD LED, if it reads a voltage, then that is your voltage across the LED. If it reads nothing, then touch it to the other side (soldered terminal) of the LED. You will need to note which side of the factory SMD LED measured a voltage, this will be your positive terminal, the other side of the LED which did NOT read any voltage will be the negative. You also need to notate the voltage value.
You want to test each SMD LED to ensure that they all read the same voltage. You also want to note the location of the positive and negative terminal for each LED.
The image below will show you my terminal locations with respect to each LED.
Picture 11 (Testing each terminal for positive voltage)
Picture 12 (My measured terminal polarities)
STEP 5:--------------------Now you can turn off your vehicle and unplug the switch pack from the harnesses. Now we need to remove the factory SMD LED’s from the circuit board. This is fairly easy and straightforward. Each factory SMD LED is glued to the circuit board with a small dab of red glue. They are also held in place by the solder on each side(NOTE: Now is a good time to turn on your soldering iron to heat up). You want to start by using your point-nosed pliers and grab the non-soldered sides of the SMD LED and rock it back and forth. You want to do this enough to pull the SMD LED from the board. When it comes off the board, it will leave the small metal terminals in the solder which we will remove in the next step. Do this for all of the remaining LED’s.
Picture 13 (You can see the LED for the lock/unlock button removed. Note the red glue which held SMD LED to board.)
STEP 6:--------------------Now we need to remove the small metal terminals left behind by the SMD LED’s. Each LED which has been pulled from the board will leave two small metal terminals encased in solder. This step is not absolutely crucial, but it is recommended, as it may not allow the new LED’s to seat properly. Grab your tweezers in one hand and your soldering iron in the other. You want to heat up the solder around each terminal and pull the terminal out with the tweezers. Once the terminal is pulled out, do the same to the remaining terminals.
STEP 7:--------------------Now this step is where the calculations come in, I will supply the calculations as well as the values I used. This is the step in which we determine how many resistors we will need and their respective resistances.
LED’s require a specific electrical current in order to work. This current depends on your specific LED. That current must be matched as closely as possible; too little current and you aren’t getting the optimum brightness from your LED, too much current and the LED’s lifespan will be drastically shorter.
When purchasing your LED’s you need to note a few crucial specifications of the LED. These values are the typical forward voltage (measured in volts, generally 3.4V or 3.5V), the typical (or testing) forward current (measured in milliamps usually, generally 20mA) and lead soldering temperature (usually a distance measured in millimeters, a temperature measured in Celsius and a time measured in seconds). These values are very important for completing this tutorial.
Now, this will get a bit technical so you need to read very carefully and try to keep up….
The factory LED’s already have resistors soldered in place so that they have the proper electrical current to light up. These resistors are NOT the values we need for our new resistors. But first we need to measure the resistance values of the factory resistors so we can get a better idea of what resistors we do need for our new LED’s. This is where the multimeter can come in handy. If you have a digital multimeter which can measure resistances, then you can just use that to measure the resistances. The other way is not as accurate. On top of each resistor is a number, that number is sort of the resistor value but not exactly. A resistor may have a 681 on top of it, and that may be 681 ohms, however, another resistor may have a 302 on top of it, but that may refer to a resistor value of 3 kilo ohms (3,000 ohms). There really is no way to know unless someone with the same exact circuit layout and resistor values has already measured the resistances and can confirm each resistor value.
NOTE: It is not necessary to solder in new resistors if the factory resistor is greater than the resistance needed for your new LED. Using a higher resistance will only make the LED dimmer than if you were to reduce the resistance. For example, if your LED requires 515 ohms and the factory resistor is 1,500 ohms, you can leave the factory resistance and the LED will be less bright than if you were to lower the factory resistance to 515 ohms. I reduced all resistances on my switch pack to the recommended values so that I would get optimum brightness from the new LED's.
Picture 14 (Measuring total resistance using digital multimeter)
Now, here’s another short lesson in electrical engineering….
The following image shows how to find the total resistance for resistors in series and resistors in parallel. Under that you can find a couple of quick examples.
Picture 15 (Calculations used to find total resistances)
Example (for resistors in series):R1 = 10 ohmsR2 = 500 ohms
Total resistance = 10 + 500 = 510 ohms
Example (for resistors in parallel):R1 = 100 ohmsR2 = 500 ohms
Total resistance = (1/100 + 1/500) = 83.33 ohms
So you can see that when you are trying to increase the resistance of some resistor, you want to place another resistor in series with it to attain a higher total resistance. To lower the value of some resistor, you want to place a new resistor in parallel with that resistor to attain a lower total resistance.
This is important because you will need to solder resistors in parallel (or series) with some of the factory resistors so you can achieve the proper value to drive your new LED’s optimally. We will get back to this in a couple of steps.
STEP 8:--------------------We need to find the perfect resistance value to drive your new LED’s. The easiest way to visit the following website:
There you can enter in your source voltage (measured in step 4), your diode forward voltage (the typical forward voltage value for the new LED, as described in the third paragraph of step 7), your diode rated current (the typical forward current value for the new LED, as described in the third paragraph of step 7). NOTE: If you have multiple LED's in an array you can just multiply the diode forward voltage for each LED times the number of LED's in said array. For example, if you have two LED’s each with a forward voltage of 3.4V, then enter a diode forward voltage of 6.8V. The calculated resistance value is the value you need to get closest to WITHOUT going under.
In the following picture, I have circled the three arrays on my driver side switch pack. The top array consists of only one resistor. The bottom two arrays consist of two resistors each. You can see in the bottom two arrays that the two LED's in each array shares a resistor (or two resistors in parallel for the middle array).
Picture 16 (Each LED array is circled in red; three total LED arrays .)
STEP 9:--------------------Now that we have our ideal resistance value for each LED array, we need to adjust each factory-soldered SMD LED to those calculated values. You will do so by soldering new resistors in parallel (or series, if necessary) to achieve new values.
Here is an example of what I’m talking about…
For my drivers switch pack, I have a middle LED array which has two resistors in parallel in between two LED’s. Each resistor value is 681 ohms, that means they have a total resistance of 340 ohms. The LED resistance calculator says I need a resistance of 345 ohms. This is the one case in which I will not need to add any new resistors. Although the resistance is slightly lower than the required value, it is not enough to shorten the lifespan of the new LED’s.
Picture 17 (My middle LED array with two 681 ohm resistors parallel)
For the bottom LED array on the drivers switch pack, I have two LED’s with a resistor in between. The resistors value is 3,000 ohms. The LED resistance calculator says I need an ideal resistance of 345 ohms. To reduce that 3,000 ohms resistance to 345 ohms, I will need to solder a new resistor in parallel. Using the parallel resistance calculations given in step 7, I found that I would need to solder a 390 ohm resistor (or the closest value I can find, without going under 390 ohms) in parallel with the 3,000 ohm resistor to achieve a total resistance of 345 ohms.
You want to find the proper resistor values for all of your resistors and solder them in as close to the board as possible. Below are some pictures of my resistors soldered on the board. You want to be sure there are no clearance issues when you slide the buttons back on the switch pack base.
Picture 18 (Side view of resistor for lock/unlock LED)
Picture 19 (View of resistor for bottom LED array)
Picture 20 (The area inside the blue rectangles are where the new LED’s will slide up into. Ensure you don’t have any clearance issues.)
STEP 10:--------------------Now that you have all of the necessary resistors soldered onto the board, you will now need to solder on the new LED’s. To start, you need to shorten the leads on your new LED’s. You want to cut off enough lead so that you have several millimeters of lead left on the LED. I left about 3 mm (where there’s a small hump on the lead itself, refer to picture 1) on the LED as this was the perfect amount. Your LED’s will need some breathing room as LED’s dissipate their heat through the base, and you want to leave some room so it doesn’t heat up the circuit board.
Now you need to solder the LED’s to the board, making sure you solder the positive lead of the LED to the positive terminal on the circuit board. You noted the terminal polarity in step 4. The longer lead on the LED is the positive lead and the shorter is the negative lead.
You want to be very careful in this step, as the LED can only be heated by the soldering iron for s specific amount of time (the values for the lead soldering temperature found in step 7). If you exceed the time value, you will likely burn out your LED and it will become unusable.
STEP 11:--------------------Now you can sit back and marvel at your fine work. Before you test out your work, it's a good idea to make sure you didn't cross networks on the circuit board when soldering. If you have a multimeter that can check for continuity then you should check all of the traces around the solder points for continuity. You're looking to see if continuity exists where it shouldn't. If you accidentally patch networks which shouldn't be patched, then the outcome could be pretty damaging and expensive. Once that's done you can take your switch pack out to the car and plug the harnesses back into the pack. Turn the car on and ensure that each LED lights up and remains lit. If an LED fails to light, then you may have the polarity of the terminals incorrect or the LED has burnt out due to excessive soldering.
Picture 21 (Success, all LED’s are lit!)
STEP 12:--------------------Now it’s time to adjust the LED’s aim and put it all back together. You need to aim the LED’s in a certain direction because they are not perfectly aligned with the buttons. You want to bend them very slightly, as in the picture below so they shine directly on the center of the buttons to allow the most possible light to shine through.
NOTE (courtesy of Slickroger):To increase the viewing angle of light from the LED's, you can also use sandpaper to scuff the surface of the LED. Simply sand the top dome-like area of the LED until it has a milky appearance. This will allow better light distribution on the buttons if the aim is slightly off.
Picture 22 (LED’s are tilted a little to aim directly at center of buttons)
Picture 23 (The LED’s bent a little forward to point directly at center of button)
STEP 13:--------------------Now you want to put the switches back onto the switch pack base and plug into vehicle harness to test the LED aiming. If the aim is satisfactory, then you can screw the entire switch pack back into the trim and press the switch pack assembly back into the door. If you are not satisfied with the aiming and light distribution, then you just have to remove the switches from the switch pack base and re-aim the LED's. All of the images I have shown throughout this tutorial are the perfect aiming for my LED's.
Some pictures of the finished product…
Modified by Pwnin O'Brien at 1:40 PM 8/19/2009