If the bulbs are connected in series then their voltages will add up to whatever the power supply outputs - this means any bulbs removed must have their voltage drop made up for with resistors. If you remove 2 bulbs at 0.5W each you will need to dissipate 1W of power if you want to maintain the same brightness in the other bulbs, for example.
To start, the full set of rear lights are all wired in parallel. So if you open up the wire loom before all of the bulbs, you'll see 4 colored wires: Black - common negative. Gray - turn signal positive. Orange - tail light positive. Yellow - reverse positive.
DRL (Daytime Running Lights) For vehicles that utilize a DRL, it is REQUIRED to use a decoder add-on for both LED products, as well as HID CANBUS kits. Most DRLs run on PWM (pulsing signal), and the decoder will smooth out the signal allowing the bulb to perform correctly. Depending on the HID or LED product, some may dim, whereas others will .do i need resistors for led headlights
