Just replaced the Shrockworks' Hella turn signals on my bumper with new ones as the ones that came with the bumper eventually burned up. The bulbs (1157A) eventually ran so hot they were melting the terminals on the bulbs themselves, blackening the plastic housing and melting the lens covers. I used just two wires that were out of the OEM daytime running lights/turn signals on each side and they worked for a few years with normal bulb changes. Eventually, terminals in the housings were overcome by the heat and needed replacement. So, got the new ones and installed them just as the previous ones were installed using just two wires (like the OEM turn signals) out of the three on the Hella harness. This time it didn't work. I had to use all three wires from the Hella harness and install my own ground wire on each side to attach to the previously unused wire on each harness. I thought that with the three wires, one filament of the bulb would act as the running light and one for the turn signal. However, only one filament does both; the other does not light but I need the three wires connected or I get a very dim "quick" flash (it gives indication that the rear bulb is blown). My question is why I needed to install a different ground this time and why both filaments are not being utilized.