Chevrolet C6H042 Owner's Manual page 121

Filter Minder Gage
(Diesel Engine) (Option)
As the filter gets dirty, the yellow indicator will begin to
rise. When it reaches 25 inches of vacuum on the scale,
the filter should be replaced.
After replacing the filter, reset the gage by pressing in
the yellow reset pin at the bottom of the gage.
If you have a diesel engine, also see your Caterpillar
Operation& Maintenance Manual.
2-78
This optional gage is in
the lower center of the
instrument panel cluster.
It monitors the engine
air filter.
Hourmeter Gage (If Equipped)
If your vehicle has this
gage, it will be to the lower
left of the steering column,
mounted on a bracket either
above or below the fuse
block. It shows the total
engine operating time.