Bosch CA Series - Page 27

Installation, Operation, and Maintenance Manual
CA Series Heat Pumps -8733851021 (2025/04) US
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Unit Troubleshooting
Problem
Mode
Check Possible Cause Action
Cooling Heating
No compressor
operation but fan
runs (Continued)
X
Is the Fault LED
blinking two (2)
times?
Low pressure fault—No or
low air ow
Check water valves and/or pumps for proper operation. Check for water coil
blockage.
Fouled or scaled water-
coil
Check for proper ow rate and water temperature, but low-water-side temp
rise in cooling.
Low pressure fault—Low
refrigerant
Check refrigerant pressure with a gauge set.
X
Is the Fault LED
blinking three (3)
times?
Freeze fault, water coil—
No or low water ow
Check water valves and/or pumps for proper operation. Check for water coil
blockage.
Freeze fault—Low water
temperature
Check water temperature—is it below 40° F entering If heat pump is con-
nected to a closed loop with antifreeze check that the “FREEZE 1” resistor
on the UPM board has been cut to set the unit to antifreeze mode (see UPM
features on page 16).
Freeze fault - low refriger-
ant
Check refrigerant pressure with a gauge set.
X X
Is the Fault LED
blinking four (4)
times?
Condensate fault— Poor
drainage
Check condensate pan for high water level. Check drain line for blockages,
double trapping or inadequate trapping.
Condensate fault—
Blocked return air
Check air lter and return air duct work for blockage. Check that there is ad-
equate space between the return air opening and walls or other obstructions
on free return applications.
Condensate fault— False
trigger
Check that the condensate sensor is mounted on the drain pan, and the
terminal is not touching sheet metal.