22
GEO16-501.4
TROUBLESHOOTING
Table 22.1 - Troubleshooting
Fault
Mode
Possible Cause
Verify
Action
Htg Clg
No power to
unit
X
X
Power Failure
No voltage at line side of compressor contactor.
Check disconnect switch and power distribution panel.
X
X
Open disconnect
switch
At heat pump disconnect, voltmeter shows voltage on
the line side but not on the load side.
Determine why the disconnect switch was opened.
Close disconnect if safe to do so.
X
X
Blown fuse / circuit
breaker tripped
Check fuses and circuit breaker.
Reset circuit breaker or replace fuses with proper
size and type. Verify total load on system and proper
fuse / circuit breaker sizing.
X
X
Low supply
voltage
Voltmeter shows abnormally low voltage at heat pump
disconnect switch (below 95% of serial plate voltage).
Call power company.
Compressor
not operating
X
X
Thermostat position
Verify that thermostat is in heating or cooling position.
Test operation of thermostat.
X
X
Defective thermostat Verify operation of thermostat; verify thermostat
signals at unit.
Replace, if defective.
X
X
Thermostat wiring
Verify thermostat wiring at unit and signals at unit.
Repair wiring, if needed.
X
X
Transformer
Check primary and secondary transformer voltages.
If no primary, verify wiring
If no, or low secondary, check transformer wiring
If wiring ok, replace transformer.
Check transformer secondary voltage circuit breaker.
Reset breaker, if tripped.
X
X
Power wiring defect
Check for loose or broken wires at compressor,
contactor and capacitor.
Repair wiring, if needed.
X
X
Locked out on safety
controls
Check controller display for fault.
Address lockout and reset controller.
X
X
Defective
compressor overload
Ensure that compressor is cool and overload has
had sufficient time to reset. Ohmmeter shows a
resistance across R & S terminals and OPEN or
infinite resistance between C & R or C & S terminals.
If windings are open or overload is faulty, replace
compressor.
X
X
Compressor motor
burn out or open
windings
Ohmmeter shows no resistance or OPEN between
common and run terminals.
*NOTE: Make sure the
compressor is rested.
Troubleshoot cause and replace motor
X
X
Defective
compressor
contactor
Voltage on line side and contactor pulled in, but no
voltage on one or both terminals on the load side.
Points damaged. Replace contactor.
Voltage on line side, 24VAC across contactor coil and
no voltage on load side.
Bad coil, replace contactor.
X
X
Loss of compressor
run signal
Voltage on line side of contactor verified and contactor
won’t pull in. No 24VAC on compressor contactor coil
when 24VAC is present at controller and controller
fuse is intact.
Replace controller.
X
X
Defective run
capacitor
Measure resistance across capacitor terminals.
If shorts exist, capacitor is defective.
Replace, if faulty.
X
X
Defective thermostat Verify operation of thermostat.
Replace if defective.
Blower does
not run
X
X
Thermostat wiring
Verify thermostat wiring at unit.
Repair wiring, if needed.
X
X
Loss of power to
motor (208/240V
units)
Verify voltage across 240VAC L1 IN & L2 IN.
If no voltage, on L1 and L2, check wiring on board and
top of contactor; repair wiring as needed.
X
X
Defective PSC motor Check line voltage at motor with G call.
If power at motor, check capacitor. Replace motor or
capacitor, if defective.
X
X
Defective ECM
motor
Verify line voltage at motor.
If power at motor, verify control signals.
X
X
Unit is oversized
Verify load calculations and unit selection.
