I looked up the manual on this unit. You can download it from here:
RV4000 Linear Series Wall Mount Radio | In-Wall Car RV Stereo
Page 17 has this. The pdf file won't let me copy the pic on the page, but the reset hole is right underneath the volume dial.
The LCD display may fail to function normally
due to the vehicle’s battery condition, and could
require resetting the radio microprocessor if:
• The vehicle has been “jump started” from a
dead battery condition.
• The vehicle battery becomes very low and is
• The vehicle battery is removed and replaced.
Should any of these conditions occur, simply
press and release the RESET button on the radio
front panel using the tip of a ball point pen. This
will reset the radio microprocessor to the original
factory settings. After pressing the RESET
button you should recheck to see if the radio
Page 20 also shows a 10 amp fuse on the back of the unit.