As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT WIG046A DEPARTED MHT-MVY NORMALLY. WHILE CLIMBING THRU 4500 FEET THE PILOT NOTED ELECTRICAL FUMES. THE PILOT DID NOT NOTICE SMOKE BUT ELECTED TO RETURN TO MHT AS A PRECAUTION AND LANDED WITHOUT INCIDENT. MAINTENANCE EVALUATED THE AIRCRAFT AND DETERMINED THAT THE ACU HAD FAILED. THE PART WAS REPLACED AND OPERATIONALLY TESTED GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.