Installing LED courtesy lights in 2005 2010 Mustang. This procedure is to provide you with the basics for installing LED strips under the dash and changing the map or courtesy lights to LED. Use the Ford Racing Illuminated Sill Plate instruction sheet to get to the wiring in the A Pillar (passenger side). Excerpts below.
Locate the Black with Light Blue stripe wire. This will be the Positive side where you will splice in your positive wire to your LED strips. For LED strips found at Advance or Auto Zone, the wires are usually a black and a black with a white stripe. The Black with a White stripe is the positive and is the wire that you will run to the Black with Light Blue stripe. The solid Black wire from the LED strip is the negative. Locate the Light Green with a Yellow stripe wire. This is the ground side and where you will splice in the negative wire to your LED strips. If you are going to replace your Map or overhead Courtesy Light bulbs with LED, you should add in a resistor to keep the LEDs from glowing dim when not on. This is a common problem others have reported when changing the bulbs to LEDs. I ordered my LEDs and Resistor from SuperBrightLEDs.com. I ordered super bright blue P/N: WLED-BHP5 Blue at $5.95 each. I also ordered qty 1, Resistor which was a 68 Ohm 10 Watt load resistor P/N: RL-2525 Marker Lamp Load Resistor at $3.95. It came with leads already soldered on which made installation a snap. To add in the resistor, splice the wires that will go to the LED strips into the wires in the A Pillar (Passenger side) as shown. Run the wires down the pillar and behind the top edge of the right side kick panel and up under the dash. Spice the resistor across the two wires where on resistor lead wire will connect to the positive wire and one resistor lead wire will connect to the negative. This simulates a
bulb in the circuit and puts the correct load in the circuit. This is needed when you change out the Map or Courtesy bulbs with LEDs and will prevent the LEDs from staying dim even when off. Mount the LED strips under the dash in a position where someone s feet will not hit them. I mounted them along the existing wiring harness and used zip ties to secure in addition to the adhesive back. The adhesive works great but in the heat of the summer, it can come lose, so the zip ties are just added protection. Run the wires across to the right passenger side of the car and splice into the wires from the A Pillar. Remember the positive wire must go to the positive on the LED strips, usually a red wire or a black with a white stripe. The negative wire must go to the negative on the LED strips. I used spade quick connect terminals so I could disconnect later if I needed. Tuck the wires under the dash to protect them and secure. Again, I used zip ties. Put the resistor somewhere that it is not touching anything. I zip tied the leads to the wiring harness and let the resistor hang in an area it will not get hit. The resistor will get slightly hot if the lights are left on for an extended period of time. This is normal. Turn the ignition key on then off and the LED strips should come on and then go off with the normal time delay matching the Map lights. This also confirms that you still have power running to the Map bulb sockets and your wiring is correct. To replace the Map or Courtesy bulbs, use a small flat head (precision) screw driver to pop out the clear Map light covers. There are three tabs on each light cover. The tabs are roughly spaced at 10:00, 2:00, and 6:00 positions with the 6:00 being towards the hood of the car. When you remove the covers, you will notice the bulbs are set back in such a manner that it is very difficult to remove them. Again, Zip Ties to the rescue. Secure a zip tie around the bulb as close to the base as possible and then use the zip tie lead to help you work the bulb out of the socket.
Once you remove the bulbs, carefully and barely insert an LED bulb into the socket. The LED bulbs are polarized meaning that there is a positive and a negative side and they will only work if plugged in with the right polarity. You may need to turn the key on to get the lights to cycle back on. Note that the LED strips under the dash should be working at this time also. If the LED turns on, then the polarity is correct and you may insert the LED fully into the socket. If it does not light, gently pull it out and rotate it 180 degrees and plug it in again. It should turn on. Replace the Map light covers. Tuck remaining wire behind the edge of the kick panel and replace all panels paying close attention to not pinch any wires. Wires should also be placed so that they do not rub on any sharp surfaces which may later cut through the insulation and cause a short circuit.