[skymstr02]

MEB09-3 titled Electrical Switches Inspection and Replacement dated May 11, 2009. Effectivity: T303, 337G-H, T337G, P337H, F337G, F337H, FT337GP, FT337HP. Purpose: to inspect switched installed in the landing light, taxi light and beacon light circuits for time in service. Switches that have been in service for 4 or more years shall be replaced and the month and year of installation shall be written on the new replacement switch. Compliance: Mandatory: shall be accomplished within the next 400 hours of operation or 12 months, whichever occurs first. NOTE: For future switch replacement intervals after compliance with this Service Bulletin, refer to the applicable airplane Service/Maintenance Manual. Revised switch replacement intervals are in development and will be issued in the next revision to the affected airplanes Service/Maintenance Manuals.

I want to interject something here, there is no such thing as a "Mandatory" service bulletin. The only things that are mandatory are AD notes and type certificate data sheet limitations. If I were to arbitrarily start replacing switches, it would be master and alternator switches as they cause many problems associated with age and high resistance.