Is there a fuse built into the unit?
Also, you could try running a temporary power wire just to make sure it's not the dash unit itself. Check the ground also.
Norman, 2008 Winnebago Adventurer 38J, W24, dozens of small thirsty ponies. Retired after 40 years wrenching on trucks! 2010 Ford Ranger toad with bicycles or KLR 650 in the back. Easy to spot an RVer, they always walk around with a screwdriver or wrench in one hand!