Problem—Warm Air from Outlets When Temperature is Set to Cold (A/C not on)
Possible Cause
Remedy
System out of calibration, front unit only.
See "Calibration Procedure."
Wiring/temperature control problem,
auxiliary unit only.
See
, Sleeper Climate Control Panel Circuit Diagnosis.
Problem—No Backlighting, Front Unit Only
Problem—No Backlighting, Front Unit Only
Possible Cause
Remedy
Dim signal not reaching the FCU or faulty
FCU.
See "Backlighting Diagnosis."
Problem—Blower Not Working, Operates at Reduced Speed, or Runs Then Shuts Off, Front and Auxiliary Units
Problem—Blower Not Working, Operates at Reduced Speed, or Runs Then Shuts Off, Front and Auxiliary Units
Possible Cause
Remedy
Blower in protection mode.
Check for fault codes.
See fault code tables, in
, for diagnosis.
If there are no active fault codes, refer to "Blower Motor" for more information.
Wiring problem.
Faulty blower motor.
Wiring problem between sleeper climate
control panel and ACU, auxiliary unit only.
See
, Sleeper Climate Control Panel Circuit Diagnosis.
Faulty blower control potentiometer,
auxiliary unit only.
See
, Sleeper Climate Control Panel Circuit Diagnosis.
Problem—Bunk Override Does Not Work, SleeperCab Only (cannot override auxiliary blower and temperature settings
from the front)
Problem—Bunk Override Does Not Work, SleeperCab Only (cannot override auxiliary blower and temperature
settings from the front)
Possible Cause
Remedy
Faulty bunk override switch.
Check switch. See "Override" for diagnosis. Verify switch operation using
DataLink Monitor template.
Wiring problem.
Check wiring between override switch and FCU.
No J1587 databus communication
between FCU and ACU.
Using ServiceLink, make sure both the FCU (MID 146) and ACU (MID 200)
appear in the ECU list. If one ECU does not appear in the list, troubleshoot
the J1587 databus. See
for more information. Also see "Override"
for diagnosis.
NOTE: Vehicles without a sleeper do not have an ACU.
Faulty FCU.
See "Override" for diagnosis.
Faulty ACU.
See "Override" for diagnosis.
Heater and Air Conditioner Troubleshooting
83.00
Symptom Driven Diagnosis
122SD and Coronado Workshop Manual, Supplement 9, June 2014
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