Fault Isolation; Heat / Defog System Troubleshooting - MD Helicopters MD Explorer Servicing And Maintenance

1. Heat / Defog System Troubleshooting

(Ref. Figure 101)
The following troubleshooting procedures are a
brief summary of heat/defog system faults
which may be encountered (Ref. Table 101).
Fault
Bleed air on with heat/defog
switch OFF
No heat/defog bleed air with
switch set to ON position.
No cabin heat with switch set
to ON.
Ejector produces excessive
amounts of hot air.
Whistle sound from under
cabin floor with heat/defog
ON. (No system shutdown by
IIDS and IIDS does not
display CAB HEAT Warning).
MD Helicopters, Inc.
Rotorcraft Maintenance Manual
HEAT / DEFOG SYSTEM

FAULT ISOLATION

Table 101. Heat / Defog System Troubleshooting
Probable Cause
Defective wiring circuit
between flow control shutoff
valve and utility control
panel.
Flow control shutoff valve
stuck open.
Defective wiring circuit
between circuit breaker and
flow control shutoff valve.
Fire/overheat bleed air leak
detection system shut down
heat/defog system through
IIDS.
(See Note)
Defective flow control shutoff
valve.
Ejector control cable(s)
assembly disconnected, out
of rig, or broken cable.
Internal ejector failure.
Bleed air coupling(s) or
tube(s) leaking. (Bleed air
leak not hitting detection
cable to cause IIDS
indication.)
Troubleshooting tables should be used with
system schematics, electrical wiring diagrams,
serviceability checks and other detailed
procedures in this and other chapters of the
manual.
Comprehensive wiring diagrams are available
in the Rotorcraft Maintenance Manual
CSP-900RMM-2 (Ref. Section 98-40-00).
Corrective Action
Test and repair wiring circuit.
Remove and replace flow
control shutoff valve.
Test and repair wiring circuit.
Find heat/defog bleed air leak
and repair leak.
Remove and replace flow
control shutoff valve.
Adjust control cable for proper
rigging. Replace broken cable.
Replace heat ejector.
Turn off HEAT switch for
heat/defog system, if sound
stops; repair coupling(s) or
replace leaking air tube.
21-40-00
CSP−900RMM−2
Ref. Section
20−60−00
21−40−00
20−60−00
21−40−10
26−10−10
21−40−00
21−40−00
21−40−00
21−40−00
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Revision 24