Bosch QV Series Installation, Operation And Maintenance Manual page 40

40 | Troubleshooting
Problem
Cooling
NO FAN
OPERATION—
CONSTANT
X
AIRFLOW
MOTOR
UNIT NOT
SHIFTING
INTO
X
COOLING AND
HEATING
8733829041 (2021/07)
Unit Troubleshooting
Mode Check
Heating
X See Action
Reversing
valve solenoid
energized
X
Reversing
valve solenoid
NOT
energized
Subject to change without prior notice
Possible
Cause
Check for 24 VAC between "G" and
"C." Check all wiring connections.
No fan
operation
Make sure that the thermostat
signal
connection plug is securely
connected.
Check all wiring connections at motor
and control box. Check that power
Loose wiring
and control harnesses are securely
connected.
Make sure that the interface board is
Interface
not damaged and that all DIP switches
board
are in the proper configuration (refer
problem
to the blower performance tables).
Check supply voltage to the motor.
Check that all motor wires are secure.
Move the "TEST" DIP switch to "ON"
and the other switches to "OFF" on
the "ADJUST" switch block on the
Faulty motor
interface board—the motor should run
at 70% torque when "G" is called. With
power off spin the motor shaft—noise,
resistance or uneven motion can be
signs of motor failure.
Check that the reversing valve
solenoid is receiving 24 VAC.
Faulty
If it is receiving 24 VAC, check the
solenoid
resistance of the solenoid—an open
circuit may indicate a burned out
solenoid.
Check that the reversing valve
thermostat wire is connected to the
Miswired/
"O" terminal of the thermostat.
faulty
thermostat
Check for a contact closure between
"O" and "R."
Check that the wires from the
Loose wire thermostat to the unit are securely
on "O" connected and that the wires from the
terminal electrical box to the reversing valve
are connected.
QV Series Heat Pumps
Action
QV Series Heat Pumps