As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING MX NOTED EMER. LIGHT JUST AFT OF THE SERVICE DOOR (EXTERIOR FUSELAGE) DOES NOT ILLUMINATE. FOUND EPSU BATTERY CHARGER NOT GROUNDING CORRECTLY AT PS36 REMOVED & REPLACED EPSU BATTERY CHARGER & BATTERY AT PS36 IAW CRJ 900 AMM 33-51-17 OPS CHECK GOOD ALL EMERGENCY LIGHTS ILLUMINATE AS REQUIRED.