Lull 944E-42, Service Manual

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Electrical System
9.158 Model 644E-42/944E-42 Rev. 6/04
9.10.10 Low Brake Pressure Indicator Troubleshooting
Check accumulator charge
valve pressures. Refer to
Section 8.7, “Hydraulic
System Testing.”
If OK
Check accumulator brake pressure switch for continuity.
• Accumulator brake pressure switch is closed when
service brake hydraulic system pressure drops below
safe operating level. (Light On)
• Accumulator brake pressure switch is opened when
service brake hydraulic system pressure rises above
safe operating level. (Light Off)
Low Brake Pressure
Indicator ON
with engine running.
Problem solved.
If OK
Low Brake
Pressure Indicator
MU4410
Check both accumulator
charge pressures. Refer to
Section 8.13, “Accumulators.”
Recharge accumulators as
necessary. Refer to Section
8.13, “Accumulators.”
Yes
Retest and see if Low Brake
Pressure Indicator is ON with
the engine running.
No
Replace switch.
0000000
RPM X 100
5
10
15
30
20
25
F
1/2
E
104
176
80
248
120
°C
°F
r/min
D
Not
OK
Not
OK
Disconnect harness at
accumulator brake pressure
switch. Indicator light
should go out.
If OK
If OK
Not
OK
Replace cab harness.
Replace switch.
Before troubleshooting any
electrical circuit, ALWAYS begin
by checking the following:
1. Fuses.
2. Battery for proper charge.
3. All connections relating to
circuit are clean and tight.
4. All grounding straps are intact
and securely fastened, refer to
Section 9.1.12, “General
Overview (Vehicle Ground
Strap Locations).”
5. Check dash panel bulbs for
proper function.