What was found
DURING CRUISE TO PUW NOTICED THAT ICE ACCUMULATION WAS MODERATE. WHEN INSPECTING THE WINGS IT DID NOT LOOK LIKE THE DE-ICE BOOTS HAD SHED ANY ICE. MONITORED THE SYSTEM AND NONE OF THE BOOT LIGHTS ILLUMINATED. WE EXITED ICING CONDITIONS. ON DIVERT TO YKM THE MANUAL MODE DID WORK. DIVERTED. LANDING UNEVENTFUL. REMOVED FROM SERVICE. REMOVED TMU IAW AMM TASK 30-11-01-000-801. INSTALLED NEW TMU IAW TASK 30-11-01-400-801, STEP 1 THRU 5C, AND STEP 5H. COMPLIED WITH REMAINING STEPS OF AMM TASK 30-11-01-400-801 AND PERFORMED FUNCTIONAL TEST OF THE AIRFRAME DEICE SYSTEM, REF TASK AMM 30-11-00-720-801. OPS TEST GOOD. AIRCRAFT RETURNED TO SERVICE.