Bosch CA Series - Page 28

Installation, Operation, and Maintenance Manual
CA Series Heat Pumps - 8733851021 (2025/04) US
28 |
Unit Troubleshooting
Problem
Mode
Check Possible Cause Action
Cooling Heating
No compressor
operation but fan
runs (Continued)
X X
Is the Fault LED blink-
ing ve (5) times?
Brownout fault— Low
voltage supply
Check the transformer primary voltage taps— Ensure it is between
the limits listed on the unit data plate.
Brownout fault— Bad
thermostat connection
Check that thermostat wiring is proper gauge and length, that it is
not damaged and that all connections at the thermostat and heat
pump are secure.
X
Is the Fault LED blink-
ing six (6) times?
Freeze fault, air coil—No
or low air ow
Check fan motor for proper operation.
Check the air lter.
Inspect the air coil for dirt/debris.
Check duct work—Are dampers closed or blocked?
Freezer fault, air coil—
Blocked return air
Check that there is adequate space between the return air open-
ing and walls or other obstructions on free return applications.
Freezer fault, air coil—
Low refrigerant
Check refrigerant pressure with a gauge set.
X X
No Fault LED— Con-
tractor Not Energized
Thermostat not calling
for compressor operation
Ensure that the thermostat is ON and calling for “Y.”
Bad thermostat con-
nection
Check “Y” connection from thermostat—Ensure that there is 24
VAC between “Y” and “C.”
Loose wire to contactor
coil
Check wiring—Ensure that there is 24 VAC across the contactor
coil.
Burned out contactor coil
Test contactor with 24 VAC (between “R” and “C”). Ohm contac-
tor coil—an open circuit indicates a burned coil.
No compressor
operation but fan
runs (Continued)
X X
No Fault LED— Con-
tractor Energized
Open compressor
overload
Check for supply voltage at the load side of the contactor. For
three-phase models check phase rotation and voltage at all three
phases.
Poor wiring connection
Look for signs of heat on the wiring insulation. Check that all wir-
ing 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.