Unit Troubleshooting - Bosch Greensource SM024 Installation, Operation And Maintenance Manual

46 | Unit Troubleshooting

UNIT TROUBLESHOOTING
Problem
NO COMPRESSOR
OPERATION BUT
FAN RUNS
NO COMPRESSOR
OR FAN
OPERATION
NO FAN
OPERATION—ECM
CONSTANT
AIRFLOW MOTOR
8733819578 (2019/02)
Unit Troubleshooting
Check Possible Cause
Open compressor overload
Poor wiring connections
No fault LED—
Contractor
Energized
Burned out compressor
Bad thermostat connection/
Power LED
faulty thermostat
blinking steadily
Low or no supply power
Faulty control transformer
Power LED OFF
No fan operation signal
Loose wiring
See Action
Faulty motor
Subject to change without prior notice
Greensource CDi Series SM
Action
Check for supply voltage at the load
side of the contractor. For 3-phase
models, check phase rotation and
voltage at all three phases.
Look for signs of heat on the wiring
insulation. Check that all wiring
connections are secure and properly
torqued.
Does compressor hum when power is
applied? If not check the resistance of
the compressor winding using the
values shown in the compressor
characteristics chart. Note that the
compressor must be cool (70ºF) when
checking the windings.
Check thermostat and wiring. Check
unit terminal block for 24 VAC
between "Y" and "C" and "G" and "C."
Ensure that the supply voltage to the
unit is within the range shown on the
unit data plate.
Check for continuity across fuse F4.
Check for 24 VAC between "R" and
"C" on the unit terminal clock. For 75
and 100 VA transformers, check that
the transformer circuit breaker has not
tripped. Check low voltage circuit for
overload conditions or short circuits
before replacing the transformer.
Check for 24 VAC between "G" can
"C." Check all wiring connections.
Make sure that the thermostat
connection plug is securing
connected.
Check all wiring connections at motor
and control box. Check that power
and control harnesses are securely
connected.
Check supply voltage to the motor.
Check that all the motor wires are
secure. With the power off, spin the
motor shaft—noise, resistance, or
uneven motion can be signs of motor
failure.
Greensource CDi Series SM Model