Welcome to right turn signal or brake to light up
Since these things normally don't happen together, I have to try to find a common element which can cause it. The first thing that comes to mind would be a bad ground. When the fan is on, it is drawing and requiring more from the grounding system. With that, I first recommend checking the ground between the battery and engine block. Make sure nothing is loose or corroded. Also, there is a body ground from the battery (see pic 1). Check it also.
Next, check the ground responsible for the fan control module and fan (G100). See picture 2. Same thing there. Make sure everything is tight, clean, and not damaged.
Let me know what you find.
Images (Click to enlarge)
Friday, April 19th, 2019 AT 8:13 PM