Bosch SM024 Installation, Operation And Maintenance Manual page 23

SM CS Series Heat
Problem Possible Cause
INSUFFICIENT Unit undersized
COOLING OR
HEATING
Loss of
conditioned air by
leakage
Airflow
Refrigerant
charge
Compressor
Reversing Valve
Operating
pressures
TXV
Moisture,
noncondensables
Compressor Ohms
Model Start Winding
SM024 1.64
SM036 1.52
SM048 1.86
SM060 1.63
SM070 1.85
Tolerance +/- 7%. All resistance values must be
measured with compressor at room temperature.
Revised 11-13
Unit Troubleshooting
Recalculate heating and or cooling loads. If excessive, possibly adding
insulation and shading will rectify the problem
Check for leaks in duct work or introduction of ambient air through
doors or windows
Lack of adequate air flow or improper distribution of air. Replace dirty
filter
Low on refrigerant charge causing inefficient operation
Check for defective compressor. If discharge is too low and suction
pressure is too high, compressor is not pumping properly. Replace
compressor.
Defective reversing valve creating bypass of refrigerant from discharge
of suction side of compressor. Replace reversing valve
Compare unit operation pressures to the pressure/temperature chart
for the unit.
Check TXV for possible restriction or defect. Replace if necessary.
The refrigerant system may be contaminated with moisture or
noncondensables. Reclaim refrigerant, replace filter dryer, evacuate the
refrigerant system, and recharge with factory recommended charge.
Run Winding
1.3
0.88
0.52
0.39
0.34
Checks and Correction
UPM Board LED Indications
Indication
Color Blinks
GREEN Solid 18-30 VAC Power is present
RED 1
RED 2
RED 3
RED 4
RED 5
RED 6 Evaporator Freeze condition
Troubleshooting | 23
Description
High pressure lockout
Low pressure lockout
Freeze sensor lockout
Condensate overflow
Brownout
8 733 920 846 (2013/11)