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Revision:
WA900-3EO
FAULT ANALYSIS CHART NOTES
13. FAULT DIAGNOSIS FOR ELECTRONIC THERMOSTAT
Refer to the Electrical Schematic Drawing for the controller.
As this is a fully sealed item it cannot be field checked for correct
operation and should be returned to TRACS if suspected to be faulty.
It is unlikely that the thermostat will fail due to internal causes and
therefore external wiring should be checked prior to deeming if failed
and especially when replacing with a new unit.
14. WIRING CHECK
In light of the above the following check can be performed to ensure
wiring is correct and must be carried out prior to replacing a blown
thermostat.
Checks should be performed in OFF-LO-HI on the female supply
plug to the thermostat from the loom.
DIAGNOSIS FOR ELECTRONIC THERMOSTATS
Test
Reason
Power present at P1.1 in LO-MED-HI
(Note - P1.1 refers to terminal No. 1)
Ensures power supply to thermostat
Continuity between P1.5 and earth.
Ensures circuit to earth.
No continuity between P1.7 and earth.
“ “
No power at P1.6 and P1.8.
Power on potentiometer (POT) control
lead will blow thermostat.
15. ELECTRONIC THERMOSTAT FAULT FINDING
COMPLAINT
POSSIBLE CAUSE
REMEDY
Continuously operates in
cooling
Potentiometer control
lead open circuit.
Internal contacts welded
closed.
Repair lead.
Check wiring, find fault
and replace.
Continuously operates in
heating. Heat illuminated
on thermostat.
Temperature probe lead
open circuit.
Internal contacts welded
closed.
Replace thermostat.
Check wiring, find fault
and replace.
Thermostat inactive
Circuit breaker tripped.
Check wiring, find fault
and reset circuit breaker.
Unit lacks capacity
Return air probe in de-ice
probe location.
Place in air stream of
return air.
Works in HEAT mode but
not in COOL .
Probes overheated
(+150
o
C)
Replace thermostat.
FAULT DIAGNOSIS
