In dash radio not working
2020 Jayco Redhawk SE 22C. Just after purchasing my unit brand new, I found the in dash radio doesn't work with the coach battery. It works fine with the ignition running, but no luck with the house battery. I checked the 7.5 amp fuse on the solenoid under the step and it checks out fine. Then I checked the voltage output, and it is at 13vdc. I also found it doesn't matter if the house power is on or not, I still get the 13vdc. Not sure if this is right or not as the feed wire to the fuse is coming from the left side solenoid post. Is there another fuse downstream going to the radio?
Any help would be greatly appreciated.
The service department at the dealer I bought it from has not been very steller and I would like to take care of this one if I can.