K 2500 Truck 4WD V8-379 6.2L DSL VIN C FI (1989)
1.
The low heat energy glow plugs have a gray colored insulator (figure 1, item 1).
2.
The hex head of the plug has a stamped in Julian date (figure 1, item 2) of 3388 or higher. The Julian date is the day of the year (such as December
3 being 337, December 4 being 338, etc.), followed by the last digit of the year (1998 being 8,1999 being 9, etc).
3.
Model identification located below the threads (figure 1, item 3) is stamped "AC 11G////U.S.A.////" (note that the low energy plugs have the
slashes //// between the letters).
In figure 2, this 11G style glow plug is not a low heat energy glow plug and should not be replaced unless standard glow plug diagnostics indicate. This
glow plug can be identified by these three characteristics:
1.
The insulator color is black (figure 2, item 1)
