Bosch LM024 Operating Instructions Manual page 23

LM CS Series Heat
Problem
NO FLOW
LOW FLOW
HIGH WATER
TEMPERATURE
LOW HEAT OUTPUT
Status LED
YELLOW "ALERT" Short Cycling
FLASH CODE 3 Compressor is
running only briefly
YELLOW "ALERT" Locked Rotor
FLASH CODE 4
YELLOW "ALERT" Open Circuit
FLASH CODE 5
Revised 01-14
HRP Troubleshooting
Possible Cause
No Power
On/Off Switch Position
Compressor Contactor
Broken or loose wires
Air Lock
Stuck pump shaft/impeller
Defective pump
Kinked or under sized water piping
Water temp limit closed
Scaled or fouled heat exchanger
Comfort Alert Module -Flash Codes
Status LED
Description
1.
2.
3.
4.
1.
2.
3.
4.
1.
2.
3.
4.
5.
6.
7.
Check power supply
Set switch to "ON" position
Engage heat pump contactor
Repair or tighten wires
Purge air from piping system
Remove pump cartridge and clean
Replace pump
Repair kink and check for proper line size
Stuck limit switch
Sensor not attached securely to line
Clean heat exchanger
Status LED Troubleshooting Information Solution
Thermostat demand signal is intermittent
Time delay relay or control board defective
If high pressure switch present go to Flash Code 2 information
If low pressure switch present go to Flash Code 1 information
Run capacitor has failed (may not be bad, verify)
Low line voltage (contact utility if voltage at disconnect is low)
• Check wiring connections
Excessive liquid refrigerant in compressor
Compressor bearings are seized
• Measure compressor oil level
Outdoor unit power disconnect is open
Compressor circuit breaker or fuse(s) is open
Compressor contactor has failed open
• Check compressor contactor wiring and connectors
• Check for compressor contactor failure (burned, pitted or
open)
• Check wiring and connectors between supply and
compressor
• Check for low pilot voltage at compressor contactor coil
High pressure switch is open and requires manual reset
Open circuit in compressor supply wiring or connections
Unusually long compressor protector reset time due to
extreme ambient temperature
Compressor windings are damaged
• Check compressor motor winding resistance
Troubleshooting | 23
Checks and Corrections
8 733 920 847 (2014/01)