Troubleshooting; Table 35: Troubleshooting - York YLAA0041 Installation Operation & Maintenance

Form 150.72-ICOM6
Issue date: 12/19/2023

Table 35: Troubleshooting

Problem
No display on panel. Unit will not
operate
Flow switch/rem stop no run
permissive
Low suction pressure fault
High discharge pressure fault
Johnson Controls

Troubleshooting

Cause
1. No 115 VAC to 24 VAC
Transformer.
2. No 24 VAC to Microboard.
3. Control Transformer defective,
no 24 VAC output.
4. Short in wire to temp. sensors or
pressure transducers.
5. Defective IPU II & I/O Board or
the Display Board.
1. No chilled liquid flow.
2. Flow switch improperly installed.
3. Defective flow switch.
4. Remote cycling device open.
1. Improper suction pressure
cutouts adjustments.
2. Low refrigerant charge.
3. Fouled filter dryer.
4. TXV defective.
5. Reduced flow of chilled liquid
through the cooler.
6. Defective suction pressure
transducer/low pressure switch
or wiring.
7. LLSV defective
1. Condenser fans not operating or
operating backwards.
2. Too much refrigerant.
3. Air in refrigerant system.
4. Defective discharge pressure
transducer.
Section 9: Service and troubleshooting
Solution
1a. Check wiring and fuse 1FU.
1b. Check wiring emergency stop contacts 5 to
L of XTBC2 Terminal Block.
1c. Replace Control Transformer.
2. Check wiring Control Transformer to
Microboard.
3. Replace Control Transformer.
4. Unplug connections at IPU II & I/O Board to
isolate.
5. Replace IPU II & I/O Board or the Display
Board.
Contact Johnson Controls
Service before replacing cir-
cuit Boards!
1. Check chilled liquid flow.
2. Check that the flow switch is installed
according to manufacturer's instructions.
3. Replace flow switch.
4. Check cycling devices connected to
terminals 13 and 14 of the XTBC1 Terminal
Block.
1. Adjust per recommended settings.
2. Repair leak if necessary and add refrigerant.
3. Change dryer/core.
4. Replace TXV.
5. Check gpm. See Operational limitations on
page 47. Check operation of pump, clean
pump strainer, purge chilled liquid system of
air.
6. Replace transducer/low pressure switch
or faulty switch or wiring. See Section 9:
Service and troubleshooting for pressure/
voltage formula.
7. Replace LLSV
1. Check fan motor, and contactors. Ensure fan
blows air upward.
2. Remove refrigerant.
3. Evacuate and recharge system.
4. Replace discharge pressure transducer. See
Section 9: Service and troubleshooting for
pressure/voltage formula on page 191.
9
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