JOHNSON CONTROLS
186
FORM 150.72-NM3 (1020)
ISSUE DATE 10/05/2020
SECTION 9 – SERVICE AND TROUBLESHOOTING
TROUBLESHOOTING
PROBLEM
CAUSE
SOLUTION
No display on panel.
1. No 115VAC to 24 VAC
1a. Check wiring and fuse
Unit will not operate.
Transformer
1FU
b. Check wiring emergency
stop contacts 5 to L of XTBC2
Terminal
Block.
c. Replace Control Transformer
2. No 24VAC to Microboard
2. Check wiring Control
Transformer to Microboard.
3. Control Transformer defective, no 3. Replace Control Transformer
24VAC output.
4. Short in wire to temp. sensors
4. Unplug connections at IPU II
or pressure transducers.
& I/O Board to isolate.
5. Defective IPU II & I/O Board
5. Replace IPU II & I/O Board
or the Display Board.
or the Display Board.
Contact Johnson
Controls Service
before replacing
circuit boards!
“FLOW SWITCH/REM
1. No chilled liquid flow.
1. Check chilled liquid flow.
STOP NO RUN PERMISSIVE”
2. Flow switch improperly
2. Check that the flow switch
installed.
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”
1. Improper suction pressure
1. Adjust per recommended
FAULT
cutouts
adjustments.
settings.
2. Low refrigerant charge.
2. Repair leak if necessary
and add refrigerant.
3. Fouled filter dryer.
3. Change dryer/core.
TABLE 27 – TROUBLESHOOTING
CONT’D
Summary of Contents for YLAA0285SE
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