As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: PILOT REPORTS APU FAULT LIGHT ILLUMINATED ON START. APU WOULD NOT START. ASSOCIATED ACRID SMELL AT ROW 33. MAINTENANCE INSPECTED AND FOUND THE APU CRANK CONTACTOR AT FAULT, INSPECTED ALL WIRES IN THE CONTACTOR AND FOUND NO WIRES DAMAGED. REMOVED AND REPLACED APU CRANK CONTACTOR IAW AMM 24-31-09. APU GROUND TEST OK.