Control panel problem

Every time I turn the ignition off the control panel on my 2011 Broadway beeps for many seconds with the message 'PSU over temp cooling down'.  But when I check the PSU in the wardrobe it's not hot.  Also it claims the vehicle battery is low when it's not - it's been checked.  I'm used to the water tank sensors telling lies but am worried this is going to be expensive to fix.  I am not technically minded at all ...