EC3 Service Manual Jan. 8, 2008
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the safety wire it is connected to will have the same voltage as the common wire. If a safety
switch is open the respective safety wire will be open (floating). Therefore the EC3 system
can identify which safety switch is open. In the event of safety fault(s), the compressor
clutch and condenser fan will be turned off and remained off until the fault code is cleared.
The evaporator blower speed will be changed to high speed and the thermostat will display
specific fault code to alert the operator.
Beside safety switches, EC3.0 also monitors two other electrical faults: low clutch voltage
and blown fuse. The EC3.0 system senses the voltage on terminal 8 (clutch power input
terminal). If the voltage on terminal drops below 11.9 vdc, EC3.0 system will turn off
condenser output and compressor clutch output and display “Lu” low voltage fault code on
the thermostat display. EC3.0 system also sense the status of fuses including 3 on-board
fuses (ATC blade type fuses), and external fuses. The system actions under these two fault
modes are also listed in Table 8.
Table 8 Faulty codes list
Fault Type
Code
Description
System Actions
HP
High pressure switch open
LP
Low pressure switch open
Fr
Freezstat open (if equipped)
Safety
Lu
Two or more safety switches open
Display fault code
Clutch output OFF
Condenser output OFF
Evap. speed High
bF
Blown fuse or
No voltage on terminal 6, 8 or 12.
Electrical
Lu
Low compressor clutch voltage
Display fault code
Clutch output OFF
Condenser output OFF
Evap. speed High
Note: “Lu” code has two possible causes.
Turn the system off to clear the fault code.
Fault code does not affect operation of tie-in condenser and tie-in compressor.
EC3.0 system automatically records the fault history to its non-volatile memory resided in
the thermostat. A special device can be used to read out the fault history.
Clutch engagement delay
EC3.0 board has built-in timer to prevent compressor clutch short cycling. After the
compressor clutch turns off, it has to remain off for 30 seconds before it turns on again.
Service timer
Every 1000 hours, the thermostat will flash “Sr” for 5 seconds when the system is powered
up. The thermostat then will return to displaying cabin temperature. The “Sr” code will be
displayed for 15 seconds every 5 minutes. This does not affect the normal operation. It just
reminds the operator the routine A/C system maintenance. The service timer can be reset by
following procedures:
Push Mode button to turn on system
Push
▲or▼ button on the thermostat to go into set point mode
Adjust the set point to 90
Push
▲ and ▼ simultaneously
Turn off the system and cycle ignition power
Turn system on to verify the “Sr” code is cleared. (Thermostat does not display
“Sr” when it was powered up first time.)
Reset the default set point to original value (see operation manual.)
