Brake lights rear blinkers quit working when turn signal is on flashes really fast
You simply have a burned out bulb or bulbs. With the key turned on turn on the directional for the left side and then the right side. Typically one bulb is blown and the opposite side works normally. Observe the normal side and note which is the flashing bulb. It is the flashing bulb on the other (malfunctioning) side that needs to be replaced. To replace the bulb you must remove the entire brakelight assembly, which isn't difficult. Open the trunk and locate the electrical harness that lines up with the brakelight assembly. Near the harness, locate the two (possibly three) nuts or wingnuts that attach the brakelight assembly to the car. Once the nuts are removed, the assembly can be pulled off the rear of the car. After replacing the bulb, be sure to test the operation of the new bulb before reassembling everthing.