Ford Parts 3S71 9278 AC Oil Pressure Switch for Ford Transit V348 A faulty oil pressure switch either keeps the red oil light on at idle (false alarm) or fails to warn you when pressure actually drops — both can mask real engine damage. This unit replaces OE 3S71-9278-AC (cross-ref 1363198, 1309298, 3S71-9278-AB) and fits Ford Transit V348 / JMC New Generation Quanshun with 2.2L and 2.4L diesel engines. It closes at the correct threshold so the dash light behaves the way it