Narrative:

Wing and engine anti-ice not on for takeoff or departure. During climb out from #1 engine cowl anti-ice light illuminated. #1 engine anti-ice switch confirmed off. #1 cowl valve open light not illuminated. Tai (thermal anti-ice indication) not displayed on upper display unit. QRH actions completed. Cowl anti-ice light remained illuminated; even with #1 throttle reduced to idle. Aircraft leveled at 16000 ft MSL. Contacted [maintenance control]; who were unable to provide guidance beyond that contained in QRH. Coordinated with dispatch for return to [departure airport]. Captain assumed PF (pilot flying) duties prior to top of descent. #1 engine thrust moderated throughout incident. Uneventful overweight landing at [departure airport].QRH procedure for this straight-forward malfunction seems incomplete. Procedure does not direct crew to confirm engine anti-ice switch position; confirm illumination of cowl valve open light; or confirm presence of tai indication on upper display unit. Lacking any secondary indications that bleed air is actually being routed to engine cowl; can engine cowl anti-ice procedure be expected to extinguish light? Is accomplishing engine cowl anti-ice procedure warranted with no secondary indications? What is the probability that multiple switch/sensor failures will occur and allow bleed air to enter engine cowl without engine anti-ice switch positioned to on? If the probability is statistically non-existent; might flight be safely continued with engine cowl anti-ice illuminated while avoiding known icing conditions when no secondary indications are present?air return to [the departure airport] deemed our safest and appropriate response to an engine cowl anti-ice light that could not be extinguished after compliance with QRH procedure.

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Original NASA ASRS Text

Title: B737 First Officer reported a persistent Engine Anti-Ice light on the climb out even after completing the QRH actions.

Narrative: Wing and engine anti-ice NOT on for takeoff or departure. During climb out from #1 engine COWL ANTI-ICE light illuminated. #1 Engine ANTI-ICE switch confirmed OFF. #1 COWL VALVE OPEN light NOT illuminated. TAI (Thermal anti-ice indication) NOT displayed on Upper Display Unit. QRH actions completed. COWL ANTI-ICE light remained illuminated; even with #1 throttle reduced to idle. Aircraft leveled at 16000 ft MSL. Contacted [Maintenance Control]; who were unable to provide guidance beyond that contained in QRH. Coordinated with Dispatch for return to [departure airport]. Captain assumed PF (pilot flying) duties prior to top of descent. #1 engine thrust moderated throughout incident. Uneventful overweight landing at [departure airport].QRH procedure for this straight-forward malfunction seems incomplete. Procedure does not direct crew to confirm engine ANTI-ICE switch position; confirm illumination of COWL VALVE OPEN light; or confirm presence of TAI indication on Upper Display Unit. Lacking ANY secondary indications that bleed air is actually being routed to engine cowl; can engine COWL ANTI-ICE procedure be expected to extinguish light? Is accomplishing engine COWL ANTI-ICE procedure warranted with no secondary indications? What is the probability that multiple switch/sensor failures will occur and allow bleed air to enter engine cowl without engine ANTI-ICE switch positioned to ON? If the probability is statistically non-existent; might flight be safely continued with engine COWL ANTI-ICE illuminated while avoiding known icing conditions when no secondary indications are present?Air return to [the departure airport] deemed our safest and appropriate response to an engine COWL ANTI-ICE light that could not be extinguished after compliance with QRH procedure.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.