Under bunk heater mystery!

I am now in a 2011 Volvo 780.
It has the factory inverter and 110ac outlets that work fine but no APU.
It has the bunk heater installed and and looks like everything hooked up to it under the bed but I can not figure out how to turn it on.
I have had the same heater with a Tri-pac and the heat was built into the control panel for the APU.

I have looked everywhere in the truck trying to figure this out because those heaters work great.
The only thing I can find is 3 aux switches on the dash that light up but not marked either.

Any Ideas??

 

Thanks Tim, I have tried that and no luck. That was with the engine off.

 

I did not look at the brand but it looks just like the one I had in a Freightliner with a Tri-Pac..

I have searched for controls and tried to follow wiring for hours..

 

I will see if I can figure out the brand this week....

 

YES!!

 

Watched the video! I had no idea!.....lol.
I hope the heater still works!
Thanks for finding that! SWEET!