No the circuit board does NOT have a voltage regulator. NOT needed.
DC Voltage supplied by batteries (or converter) can be 10.5V to 15.4V
AC Power can be 108V to 132V
'HE' fault means the electric heater elements failed OPEN
So problem is either with one or both heater elements (should test at 64 Ohms each), elements lead connections (loose/dirty) or circuit board
Are you getting ANY High or Low AC Fault codes?
Is it time for YOUR Medication or Mine?
Dodge 3500 w/Tractor Motor & NUWA 5vr
US NAVY---USS Decatur DDG-31