APU with possible inverter (2018 Volvo VNL 760)

This might be a stupid question, but I'm going crazy trying to figure it out.

For the record, I have never had an APU before, so I really don't know much about them.

I was just assigned a truck that I was promised had both an APU and an inverter in it. It has an APU (that only works if the truck is not running), and one power outlet under the bed (the one usually in the closet is not present). I do not see any sort of inverter, and where the controls for the inverter usually are, is the control for the APU instead.

I can't get the power outlet to work at all. I hit the reset button, I looked under the bed hatch to make sure it was connected, I followed the cord that was coming out of the electrical box on the backside of the outlet, and it went inside a big metal box that is screwed shut. I went outside and opened the hatch from the side, and it is closed off from that side too. I have no idea where the cord ends up. When the truck was off, I turned the APU on, and the outlet still wouldn't work.

I called Penske, which is where my company got the truck from. The technician wasn't sure, but he suggested the outlet was wired straight into the battery. Is that a thing? And, if so, why even have an inverter if you can plug an outlet directly into the battery?

I asked the guy who had this truck before me, and he wasn't sure, but he suggested the outlet might only work when the truck is on shore power. Which is even more inconvenient than not being able to use it while running.

In any case, I need the outlet to work! Even if the truck is running! And especially if I don't have shore power! The whole point of my needing it was to make my own coffee during the last hour my co-driver is driving, so I'm ready to go when he's done. We can't always count on a truck stop being where we need it to be, nor do I ever wish to drink the dreck most truck stops call coffee! We also basically never have access to shore power.

Anyway. Would someone please advise if they think there is hope for the outlet to work for me? And what I might do to it to make that happen?

Thank you!

 

I actually don't see one! There is a plug for the engine heater, but I don't see another plug out there.

 

Hrm. That is an interesting observation. I noticed in my last truck, when I tried to plug my white noise machine and bluetooth adapter into the power with the inverter on, all I got was a humming too!

Anyway. I just checked the AM stations, and they do play, but they have what sounds like a helicopter playing alongside them. Not sure if that's normal, or not, because I don't usually listen to the radio (AM or FM) in the truck, plus this is the first time I've been in this particular truck.

 

I appreciate all of the info, but I can't find an inverter anywhere. Only the outlet, which has an electrical box on the backside of it, and a cord coming out of it that travels back and hides behind something I cannot see.