As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
YELLOW HI TEMP LIGHT ILLUMINATED IN FLIGHT. RETURNED TO MEMPHIS. MAINTENANCE REPLACED YELLOW ISOLATION VALVE IAW AVRO AMM 29-10-14 (201) (P/N HTE9531-3). OPS CHECK GOOD. HI TEMP LIGHT REMAINED EXTINGUISHED USING BOTH ENGINE AND A/C PUMPS.