APU Runs for a few minutes, shuts off with red ENG light

I can get it to run if I hold down the power button and turn it off inside the sleeper then turn it back on. The light goes away but it still starts up and shuts off after about a minute or so. I will check into the reset switch, I don't believe it has the Arctic package. This is my first truck with an APU so I don't know much about it at all. I will check for the reset switch and see if it just needs a reset.

 

Where are the fuses at?

 

I've checked for a reset switch on the box under the bunk. There is a very large box with a small box mounted on top. The top small box has a diagram of the electrical setup within it and a whole ton of wires going into it. There is no reset switch on either box. On the outside anyway. My screw driver is too tall to get to the back screws of the top smaller box where the fuses are located so next chance I get ill be buying one and popping open that small electrical box to check for said switch and check the fuses. They may have closed some coolant lines when they were tearing apart the dash to get the HVAC fixed. He did mention that he unhooked and pinched off the heater core which means he may have closed the valves at some point if they're connected. It's gotta be that, I don't see why anything else they did would cause any change in the APUs behavior. Now just to find these coolant lines...

 

I've checked the outside thoroughly, there is no reset button on the box. I've checked the inside thoroughly, there is no reset button on the inside of the box

 

I've attached what my box looks like.