9. TROUBLE-SHOOTING AND REPAIR
49
9.4
TROUBLE-SHOOTING GUIDE
,
continued
SYMPTOM
PROBABLE CAUSE
REMEDY
Low output voltage when
Defective inverter
Replace power
unit is in STANDBY mode.
transistors.
board assembly.
SYMPTOM
PROBABLE CAUSE
REMEDY
No output voltage when attempting
Battery breaker off.
Switch battery breaker on.
to transfer from LINE to STANDBY;
“Clicking” sound from contactor.
Battery voltage below
Check battery voltages; check
recharge acceptance
terminal connections; charge or
level.
replace batteries if necessary.
High resistance at
Check battery open circuit
battery connector.
voltages; clean and tighten each
connection; replace faulty
battery.
Main circuit module incorrectly
Remove, clean and reseat
seated in back plane connector.
assembly.
Faulty logic.
Replace main circuit module.
Inverter transistors damaged.
Replace power board.
Faulty standby relay.
Replace relay K101.
SYMPTOM
PROBABLE CAUSE
REMEDY
module does not transfer
Low AC line voltage.
Use voltmeter to verify
from STANDBY to LINE mode
nominal voltage at receptacle.
when input power is restored;
Contactor “clicks” periodically.
High impedance AC line.
Check all connections.
Check for correct wire gauges;
Shorten cables to AC utility.
Faulty logic.
Replace main circuit assembly.
SYMPTOM
PROBABLE CAUSE
REMEDY
Batteries will not charge.
Battery breaker off
Switch battery breaker on.
Faulty batteries.
Check open circuit voltage;
Check voltage under load;
Check terminals and connecting
wires. Replace faulty batteries.
Charger fuse F301 open.
Replace 10 Amp fuse.
(on main circuit module)
Faulty charger circuit.
Replace main circuit module.
Charger transistors damaged.
Replace power board.
