Was flying into Sullivan County this weekend and had to run the RNAV instead of the ILS. ATC advised there was a NOTAM for the weather sensors (which we had already confirmed.) Does an ILS approach require that the airport have functioning weather or is this just a case of a 2-for-1?
Whether or not an ILS may be conducted without proper weather reporting will depend on the regulations under which the flight is operated.
In simple terms, a flight operated under 14 CFR 91 may perform an ILS without this weather reporting.
This may also be allowed under the eligible-on-demand rules of 14 CFR 135, if all pertinent requirements are met.
Otherwise, a flight operated under 14 CFR 135 or 14 CFR 121 will generally not be approved to conduct an ILS without approved weather reporting.
This answer applies under FAA jurisdiction.