Why does the right side get a weak signal when the left turn signal blinks and the left signal stay on solid when the headlights are on?

One of the signal bulbs on the left side has its ground terminal disconnected. The circuit is completed through the headlights and right turn wiring. Look for the following: - Corroded bulb socket - Loose socket holder (often the ground is made through the metal-to-metal contact) - Damaged wiring Turn on the headlights to find which bulb. That bulb won't light when the signal is turned on.