Yes the fuse controls both sides and the hazard flash also. The relay also controls both sides. So that leaves the bulbs as the problem. One of the bulbs on one side is not matched correctly in its wattage usage. If you have changed any recently then recheck that bulb against the other side and see what the part number on each bulb is for the newest one is not the correct type for your car. Most people do not know that though there are two bulbs side by side at the auto parts store shelf and they look like the same bulb that the bulbs are designed for different applications. If this problem existed before you bought the car you may need to check the owners manual for which bulb your car should have and find the one that is wrong and replace it.