EC3 Service Manual Jan. 8, 2008
6
Slave board configuration
In some large systems where the electrical load exceeds the current capability of a single
board, a slave board can be used. A typical wiring diagram is 5031xxxx. In a slave system,
the switches are connected to the master board and the slave board is connected to the master
board through a harness 701442. The slave board mimics the actions of the master board.
The slave board normally is used to drive the additional evaporators and condensers.
Trouble shooting
Use Table 8 to identify the problem if there is a fault code. Other common problems are
listed in Table 9. Refer to previous sections for detailed action procedures.
Table 9 Trouble Shooting
Symptom
Probable causes
Action
Switch does not turn on
No power
Check COM LED
Check terminal 5 for +12vdc
and 10 for ground
Faulty communication cable
Replace cable
Faulty switch
Replace switch
Faulty board
Replace board
Clutch does not engage
Tset> Tin
Adjust set point
Faulty external temperature
sensor
Replace temp. sensor or
sensor cable
Bad connection
Check LED on board and
voltage on terminal 1
Faulty board
Replace board
Fan / Blower do not run
Bad connection
Check LED and power
output terminal
Faulty board
Replace board
Blower does not stop
Faulty board
Replace board
Fault code persists
Bad connection
Check safety harness
connections at evap. & board
Fault condition persists
Check pressure and voltage
1000 hr service timer
Reset service timer
Faulty board
Replace board
Thermostat shows Lo all the
time
Low cabin temperature
Verify cabin temperature is
below 60ºF
Temperature sensor cable
short
Verify shortage
Repair or replace cable
Faulty temperature sensor
Replace sensor
Thermostat shows Hi all the
time
High cabin temperature
Verify cabin temperature is
above 90ºF
Temperature sensor open
circuit
Verify open circuit
Repair or replace cable
Faulty temperature sensor
Replace sensor
