Bunk Override Diagnosis
Test
No.
Test
Test Procedure
Test Result
Action
1
Check bunk override
function with DataLink
Monitor Test.
Open the DataLink Monitor
template for this system.
Turn the ignition on.
Set the front blower to high and
the temperature to hot.
Set the auxiliary blower to off
and the temperature to cold.
In the template, press the bunk
override ON test button.
The ACU bunk override mode
annunciator state should be ON
and the auxiliary blower and
temperature settings should
match the front settings (can be
observed on the template. Note
that it takes about a minute for
the settings to completely
change.)
The ACU bunk override
mode state is ON and
auxiliary blower and
temperature settings
closely match front
settings.
Go to test no. 3
.
The ACU bunk override
mode state is ON and
auxiliary blower and/or
temperature settings do
not match the front
unit.
Replace ACU, then
go to test
no. 5
.
The ACU bunk override
mode state is OFF or
NA/ERR.
Go to test no. 2
.
2
Verify J1587
communication.
Connect ServiceLink to the
vehicle. Check if both the FCU
(MID 146) and ACU (MID 200)
appear in the ECU list.
Both ECUs appear in
the ECU list.
Go to test no. 3
.
One or both ECUs do
not appear in the ECU
list or ServiceLink is
unable to connect to
vehicle.
Troubleshoot and repair J1587
databus. Refer to
for
more information.
Go to test no.
5
.
3
Check override switch
operation.
Open the DataLink Monitor
template for this system.
While observing the bunk
override switch annunciator in
DLM, press the switch to the
momentary on position, then to
the momentary off position.
The annunciator should indicate
switch position. When the switch
is in the normal position, the
annunciator should indicate NA/
ERR.
Switch functions as
described.
Go to test no. 4
Switch does not
function as described.
Check override switch and
wiring. Repair as necessary. If
okay, replace the FCU.
Go to
test no. 5
.
Heater and Air Conditioner Troubleshooting
83.00
Symptom Driven Diagnosis
122SD and Coronado Workshop Manual, Supplement 9, June 2014
350/12