GMC T-Series 1999, Owner'S Manual, Page: 53 / 344

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2-17
Engine Checks Before Operating
When you’ve started your engine, let it run for
20 to 30 seconds before you put a load on the engine.
But don’t leave the vehicle while the engine is running.
During this warm
-
up period, check your warning lights
and gages:
D If oil pressure doesn’t begin to rise within
15 seconds of starting, stop the engine and
find the cause.
D If the engine coolant temperature gage needle goes
into the hot area on the gage, stop the engine and
find the cause of the overheating.
D If you have air brakes, the dual
-
needle air pressure
gage should read at least 105 psi (720 kPa) for both
service systems before you try to move the vehicle.
When air pressure is below 60 psi (420 kPa), the
LOW AIR light will come on and you will hear a
tone alarm. If the pressure doesn’t build up or drops
during warm
-
up, stop the engine and find the cause
before you try to move the vehicle. Recommended
air pressure before actually driving away is
120 psi (830 kPa).
D The charging system light should come on when the
ignition switch key is turned to ON or START and
should go out when the engine is running above idle.
If the light doesn’t go out or comes back on during
normal engine operation, have the charging system
checked right away. (This light tells you if the
generator is not charging; it doesn’t reflect the
condition of the battery.)
D The voltmeter charge indicator gage tells you the
condition of your battery’s charge. The gage should
be in the center area during engine operation. The
red area on the left indicates an undercharge
condition; the red area on the right indicates an
overcharge. If the gage is in either red area, have the
battery and charging system checked right away.