Slider Reference not registering

I have 3 status bars in my projects with sliders attached to the background images. I dragged the fill images into the slot and the sliders were working when I adjusted the values in the editor. Then I wrote a short script that had functions that would set the values of the sliders, and attached it to the player game object. I dragged the sliders into their slots in the editor, but when I start the game, I get a Null Reference Exception for all of the sliders. I'm not sure if I referenced the sliders correctly, Unity's pretty new for me.

I tried to reference the sliders like this:

 public Slider repairBar;
 public Slider capacitorBar;
 public Slider batteryBar;

And then dragged the sliders into the slots in the editor.