ISTR this field code was required because you had the Excel workbook open when the merge was done, and that was messing with the formats. The 'N/A' was for those cases when the lights would not be used.

Try:

{IF{MERGEFIELD LIGHTS_ON_TIME}= "" "N/A" {MERGEFIELD LIGHTS_ON_TIME \@ "h:mm AM/PM"}}

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]