Glow Plug Testing: Notes
WARNING: This page is about a different car, the 1995 Ford RV Cutaway, 1995 Ford Econoline, 1995 Ford Cutaway, and 1995 Ford Club Wagon. However, it is still accessible from the selected car via links, so may be relevant.
WARNING:
DO NOT by-pass the timed pulse function of the glow plug system. A constant 12-volt current to glow plugs will cause them to overheat and fail within seconds, possibly resulting in severe engine damage.