Bosch LV009 - Troubleshooting Fan Operation; PSC and ECM Fan Motor Issues

Troubleshooting | 37LV Heat Pump Series
8 733 905 683 (2016/09)LV Heat Pump Series
No compressor operation
but fan runs
X X
No fault LED -
contactor energized
Open compressor
overload
Check for supply voltage at the load
side of the contactor. For 3 phase
models check phase rotation and
voltage at all 3 phases.
Poor wiring connections
Look for signs of heat on the wiring
insulation. Check that all wiring
connections are secure and properly
torqued.
Burned out compressor
Does compressor hum when power
is applied? If not check the
resistance of the compressor
windings using the values shown in
the compressor characteristics chart.
Note that the compressor must be
cool (70° F) when checking the
windings.
No compressor or fan
operation
X X
Power LED on
Bad thermostat
connection / faulty
thermostat
Check thermostat and wiring. Check
unit terminal block for 24 VAC
between "Y" and "C" and "G" and "C".
Power LED off
Low or no supply power
ensure that the supply voltage to the
unit is with in the range shown on
the unit data plate.
Faulty control transformer
Check for 24 VAC between "R" and
"C" on the unit terminal block. 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.
No fan operation - PSC
motor
X X
Fan relay energized
Faulty motor
check supply voltage from the fan
relay to the motor. Check that all
motor wires are secure. With power
off spin the motor shaft - noise,
resistance or uneven motion can be
signs of motor failure.
Fan relay not
energized
No fan operation signal
Check for 24 VAC across the fan relay
coil. Check all wiring connections.
Bad fan relay
If the relay coil is energized but the
relay does not pull in, check the
resistance across the relay coil - an
open circuit is an indicator of a faulty
relay.
No fan operation -
constant torque motor
X X
No fan operation signal
Check for 24 VAC between "G" and
"C". Check all wiring connections.
Loose wiring
Check all wiring connections at
motor and control box.
Faulty motor
Check supply voltage to the motor.
Check that all motor wires are
secure. With power off spin the
motor shaft - noise, resistance or
uneven motion can be signs of motor
failure.
UNIT TROUBLESHOOTING
Problem Mode Check Possible Cause Action