9
−
17
62-11389
Check door switch
wiring for an open.
Did you find and cor-
rect the condition?
YES
YES
NO
NO
NO
NO
NO
NO
NO
YES
YES
YES
NO
YES
YES
YES
NO
NO
YES
YES
START HERE
Check the fuel/speed ac-
tuator and plunger for correct operation.
Did you find and correct the condition?
Unit may be running old soft ware. Upgrade
software from http://www.transcentral.carrier.-
com. Did you find and correct the condition?
Check system suction pressure at compressor. Is suction pressure -2 psig or lower?
System OK
System OK
Check engine coolant temperature. Is coolant temperature 122
°
F (50
°
C) or below?
Is unit in defrost?
Is the the RAT 95
°
F or higher OR the SAT 115
°
F or higher?
Does the unit have a
door or remote switch?
Is the switch configured
for low speed?
Is the door
open?
Are alarms A122 & A123 both present
OR alarms A137 & A138 both present?
Is setpoint 10
°
F or lower in the com-
partment with the active alarms?
Is the unit in Continuous operation?
Is the setpoint
10.5
°
F or higher?
Is return air temp equal to
or colder than setpoint?
Is selected probe temp
/- 3.6
°
F of setpoint?
Is speed relay LED27
illuminated on micro?
The micro is calling for low speed
operation. If you believe this is not
correct, review your testing with
your supervisor before changing
microprocessor.
Is the F2 fuse blown?
Check the F2 circuit
for excess amp draw
or short to ground. Did
you find and correct
the condition?
Is there voltage at QC3?
Check for proper operation of
the speed relay. Is the relay
operating properly?
Replace relay. Did you
find and correct the condition?
Review the test results
with your supervisor. If
necessary, go to the
beginning of the tree
and test again.
Micro is calling for high
speed. Is there 12V at FSA
and ENSCU pin 16?
Check for proper operation
of the Engine Speed Con-
trol Unit or FSA.
Check wiring and connections from QC3 to ENSCU or FSA.
Did you find and correct the condition?
Repair or replace ENSCU or
actuator as needed.
Does the message center show
“FORCED LOW ENGINE SPEED?
Check speed overrides, Section 4.8.3.
Did you find and correct the problem?
Has the unit restarted from an Off Cycle due to any
override other than compartment temperature?
System OK
YES
NO
NO
NO
YES
NO
YES
YES
NO
YES
NO
YES
YES
Is the unit in
Start-Stop
operation?
YES
Has the unit been running less that the selected
Continuous Operation High Speed Delay minutes?
YES
Has the unit been running less than the selected Start-Stop
Operation High Speed Delay minutes?
NO
NO
YES
NO
NO
YES
YES
NO
YES
YES
YES
NO
NO
YES
NO
YES
YES
YES
NO
NO
NO
NO
NO
NO
YES
YES
YES
Figure 9
−
8 Micro Diagnostic Tree - Condition 4 - Unit Will Not Run In High Speed
