Service manual

Group 170 Preventive Maintenance
Engine Low Idle
Note: For further information refer to literature in Func-
tion Group 3.
Record the engine low idle speed. Listen for idling prob-
lems such as surging, missing or unusual noise. See
each engine manufacturer’s specification for correct idle
speed.
Record low and high oil pressure.
Check Low Air Warning Switches
Note: For further information refer to literature in Func-
tion Group 8.
Pump the brake pedal while observing the air gauges.
As the air pressure is lowering, verify the compressor
governor cut-in pressure and the low air warning
switches cut-in pressure. Check that both indicator lights
in the lower right corner and the Master Warning indica-
tor lights up and make sure the buzzer sounds.
Governor cut-in should be at 790 ± 35 kPa (115 ± 5 psi).
The low air warning switches should close at a minimum
pressure of 420 kPa (60 psi).
Check Manifold Dash Valve
Note: For further information refer to literature in Func-
tion Group 8.
Start the manifold dash valve check by pulling out the
yellow knob (Parking). At the same time the red knob
(Trailer air supply) should also pop out. Press both
knobs in.
Note: The gauges should only be used for general refer-
ence. Gauge accuracy below 275 kPa (40 psi) is low.
Lower the air pressure, by pumping the foot brake valve,
to the point where the red knob pops out. Verify that this
happens at a pressure of 275 ± 35 kPa (40 ± 5 psi).
Hold the red knob in manually and decrease the pres-
sure further. At a pressure of 210 ± 35 kPa (30 ± 5 psi),
a tripper valve starts to exhaust the air supply to the
trailer. This is the non-override function working. Release
the red knob.
Continue to decrease air pressure until the yellow knob
pops out. This should happen at a pressure of 170 ± 35
kPa (25 ± 5 psi). Now try to push in both knobs. They
should not stay in on their own.
94