One of the bulbs in the dome light of [Pete’s] car burnt out. These were a bit hard to get at for replacement so he thought he’d try something that would last longer, and have no problem standing up to the vibrations that go along with automotive electronics. But plug-in LED replacements cost more money than he was willing to spend. Luckily there was a dollar store next door to the auto part shop, so he bought three LED touch lights for the dome and cargo bulbs.
After cracking them open he found that the LEDs were wired in parallel. He needed to put these in series in order to take advantage of the voltage drop. After de-soldering the bulbs he measured the characteristics of one, then calculated the voltage drop and resistor value using a worst case scenario of 14V to avoid damage to the light when the engine is revving high. From there he cut the traces on the board and rewired them. The reworked module fits nicely and as you can see in the image, gives a more pleasing light color than the orange of the stock bulb.