JOHNSON CONTROLS
197
SECTION 9 – SERVICE AND TROUBLESHOOTING
FORM 150.72-ICOM6
ISSUE DATE: 08/03/2022
9
TROUBLESHOOTING
TABLE 36 -
TROUBLESHOOTING
PROBLEM
CAUSE
SOLUTION
NO DISPLAY ON PANEL. UNIT
WILL NOT OPERATE
1. No 115 VAC to 24 VAC
Transformer.
1a. Check wiring and fuse 1FU.
1b. Check wiring emergency stop contacts 5 to
L of XTBC2 Terminal Block.
1c. Replace Control Transformer.
2. No 24 VAC to Microboard.
2. Check wiring Control Transformer to
Microboard.
3. Control Transformer defective,
no 24 VAC output.
3. Replace Control Transformer.
4. Short in wire to temp. sensors or
pressure transducers.
4. Unplug connections at IPU II & I/O Board to
isolate.
5. Defective IPU II & I/O Board or
the Display Board.
5. Replace IPU II & I/O Board or the Display
Board.
Contact Johnson Controls
Service before replacing cir-
cuit Boards!
FLOW SWITCH/REM STOP NO
RUN PERMISSIVE
1. No chilled liquid flow.
1. Check chilled liquid flow.
2. Flow switch improperly installed.
2. Check that the flow switch is installed
according to manufacturer’s instructions.
3. Defective flow switch.
3. Replace flow switch.
4. Remote cycling device open.
4. Check cycling devices connected to
terminals 13 and 14 of the XTBC1 Terminal
Block.
LOW SUCTION PRESSURE
FAULT
1. Improper suction pressure
cutouts adjustments.
1. Adjust per recommended settings.
2. Low refrigerant charge.
2. Repair leak if necessary and add refrigerant.
3. Fouled filter dryer.
3. Change dryer/core.
4. TXV defective.
4. Replace TXV.
5. Reduced flow of chilled liquid
through the cooler.
). Check operation of pump, clean
pump strainer, purge chilled liquid system of
air.
6. Defective suction pressure
transducer/low pressure switch
or wiring.
6. Replace transducer/low pressure switch or
pressure/voltage formula.
7. LLSV defective
7. Replace LLSV
HIGH DISCHARGE PRESSURE
FAULT
1. Condenser fans not operating or
operating backwards.
1. Check fan motor, and contactors. Ensure fan
blows air upward.
2. Too much refrigerant.
2. Remove refrigerant.
3. Air in refrigerant system.
3. Evacuate and recharge system.
4. Defective discharge pressure
transducer.
4. Replace discharge pressure transducer.
for pressure/voltage
.
