(b)(4) the sample was returned for evaluation.A visual exam was performed and there were no defects observed.Functional testing was performed and the unit was connected to 110vac.The unit passed the initial power connect test and navigated through the power-on self-test (p.O.S.T.) with no issues.During the temperature display accuracy test the unit displayed the correct temperatures and properly alarmed in the high temperature scenario.The unit was prepared for the functional bench test where water, an adult breathing circuit (880-36kit), 2-3 lpm of air pressure, and a 382-10 universal water column was connected to the unit for a real time operational scenario.This time the unit did not pass all pre-operational self-tests.Both wire indicator arrows were flashing indicating that the unit was not detecting the proper resistance from the heated wire cables.The resistance across the inspiratory (blue) and expiratory (yellow) wires of the lab inventory adult breathing circuit measured 13.5 ohms and 13.2 ohms, which is within the normal operating range.The 24v power supply and the 5v power supply were both functioning properly and were outputting 24.77 vdc and 4.971 vdc respectively.Since the unit was able to pass p.O.S.T.And the resistance of the breathing circuit was found to be within range, the root cause of this failure is likely an issue with the heated wire current sense circuit.A device history record review was performed and no relevant findings were identified.The complaint has been confirmed.The investigation revealed a defective heated wire current sense circuit.Since the neptunes are 100% functionally tested during manufacturing assembly, it is unlikely that the failure was present at the time of release.A device history record review was performed with no evidence to suggest a manufacturing related issue.The unit was manufactured in 2012 and was designed for a minimum of 5 years.The root cause for the failure is normal wear.
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