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Under what conditions do York screw compressors require component replacement in order to allow the unit to operate again? What are some simple methods for quickly identifying the cause of faults in the unit? Next, Gonglenghui will explain 33 common fault checks and solutions for York RWB II units; feel free to send a private message if you have any questions! I. Causes of no display on the screen and methods to resolve them: 1. Check the 10-amp fuse in the power supply circuit of the control center to confirm that it is intact and properly installed. 2. Turn off the power, open the cover, and check that all connections are secure and reliable. II. Causes of oil pump failure to start and troubleshooting methods: 1. Check the HAND‑OFF‑AUTO switch of the oil pump; it should be set to automatic mode, and the emergency stop switch should be closed. 2. Check whether the power supply for the oil pump is in place, whether the fuse of the output module is intact, and whether the contactor is functioning properly. 3. If the auxiliary contact of the oil pump contactor is closed and the feedback signal for the oil pump reaches the input module, yet the oil pump still does not operate, please contact the industrial cooling support team for assistance in resolving the issue online. III. Causes and solutions for the issue where the oil pump is operating but the compressor does not start: 1. Verify that the HAND‑OFF‑AUTO switch of the oil pump is set to the automatic mode. 2. Verify that the spool valve has been unloaded to below 5%; if it cannot be unloaded, the oil circuit needs to be checked. 3. Verify that the compressor start output module is functioning properly, that the module fuse is in good condition, and that the start power supply is providing power. IV. Causes of and solutions for the fault of disconnected auxiliary contacts of the compressor: 1. If the motor does not start, check whether the compressor start module and fuses are in good condition, and verify whether the compressor start relay is functioning properly. 2. If the motor has been started, check the feedback signal contacts of the motor starting device to see if they are in good contact. V. Causes of failure and troubleshooting methods for the oil heater not working: 1. If the oil heater is activated only when the compressor is shut down and the oil temperature in the oil separator is low, it is necessary to check whether the conditions for its operation are met. 2. Check the oil heater output module and fuse. 3. Check the 15-amp fuse and contactor on the oil heater circuit. VI. Causes and solutions for the fault where the slide valve cannot be loaded/unloaded: 1. Verify that the slide valve is in automatic control mode, and that there is indeed a requirement to load/unload it. 2. Check the load signal output module and fuses, as well as the solenoid valve in the load oil circuit. 3. Check the unloading signal output module and fuse, as well as the solenoid valve in the unloading oil circuit. Note: Setting the C.C. value correctly is a prerequisite for the proper operation of the slide valve. VII. Causes and solutions for the failure of the slide valve to increase/decrease load: 1. Verify that the slide valve (slider) is in automatic mode. 2. Check the overload signal output module and fuses, as well as the wiring of the overload oil circuit solenoid valve. 3. Check the load-reduction signal output module and fuses, as well as the wiring of the load-reduction oil circuit solenoid valve. VIII. Causes of failure and troubleshooting methods for the non-functioning liquid spraying solenoid valve: 1. Verify that the opening degree of the liquid spraying solenoid valve and the liquid supply volume are normal. An excessive supply volume of fluid can cause the oil temperature to drop too low, and the control center will shut off the liquid injection solenoid valve. 2. Check the signal output module and fuse of the liquid spraying solenoid valve, as well as the wiring of the liquid spraying solenoid valve. IX. Causes and solutions for the failure of the high VI solenoid valve to operate: 1. Verify whether the VI value is higher than 3.4. The high VI spray solenoid valve will only activate when the value reaches 3.4. 2. Check the signal output module and fuse of the high VI spraying solenoid valve, as well as the wiring of the high VI spraying solenoid valve. X. Causes and solutions for the failure of the economizer solenoid valve not functioning: 1. Verify that the spool is in a position of 90% or higher. Only when this value is reached will the economizer solenoid valve open. 2. Check the economizer solenoid valve signal output module and fuses, as well as the wiring of the economizer solenoid valve. XI. Causes of failure and troubleshooting methods for a non-responsive alarm device: 1. Confirm that a fault has occurred previously. 2. Check the alarm signal output module and fuses, as well as the operation status of the alarm devices, such as buzzers and warning lights. XII. Causes and solutions for the issue where the control panel does not respond to remote control signals: 1. Check the control panel to ensure that the compressor and the loading/unloading functions are set to automatic mode. 2. Check whether the input modules 2, 3, and 4 used for remote control are connected correctly. 3. If all input modules 2, 3, and 4 are powered on but remote control still does not work, please contact Gonglenghui. 13. Causes and solutions for the fault of forced unloading when the motor is operating at low load: 1. The function of the current transformer is to convert the alternating current from the motor into a direct current signal, which is then sent to the control center; this signal displays the percentage of the motor’s operating current compared to its full-load current. If the current percentage (%FLA) read from the display is abnormal, that is, if the displayed value **exceeds the actual value, it will cause the unit to be forced to shut down. 2. At this time, it is necessary to check whether the output signal of the current transformer is normal and whether the setting of the ratio is correct. If everything is confirmed correct but recovery is still not possible, please contact Gonglenghui. XIV. Causes and solutions for abnormal pressure display faults: 1. Fluctuations in the readings of the pressure sensor lead to abnormal pressure displays. Shut down the machine for inspection: Balance the suction pressure, exhaust pressure, and oil pressure of the unit, and check whether the readings of these three values are consistent. 2. Drainage check: Close the valve that connects the pressure sensor to the system, and open the valve that leads to the atmosphere. If the displayed reading is not equal to atmospheric pressure, it indicates a fault with the sensor. Note: Sensor readings allow a 1% error. 15. Causes of garbled text on the display screen and methods to resolve them: 1. Check whether the grounding in the control center is effective, and whether the connections between the main control board and the display board are correct and reliable. 2. Removing the 10-amp fuse on the power supply circuit of the control center for about 15 seconds and then reinstalling it can serve to reset it. 16. Causes and solutions for abnormal noises and vibrations in compressors: 1. The main oil supply valve may be closed; open this valve. 2. The coupling may be loose; tighten the coupling. 3. The alignment between the motor and the compressor is off; re-alignment is required. 4. If liquid slugging occurs, the system needs to be adjusted. 5. If the bearing is worn or damaged, please contact Gonglenghui, or consult previous articles for technical information. 17. Causes and solutions for the failure of the slide valve and/or slide check valve (slider) to function: 1. Check the oil circuit four-way valve, resolve the issue or replace it. 2. Check the wiring and resistance value of the indicator potentiometer for the slide valve and check valve. 3. Check whether the compressor is operating at normal oil pressure. 4. The piston is locked during disassembly; please contact the process cooling department. 5. If the slider seal ring is worn or damaged, please contact Gonglenghui. 6. The pilot pin is locked due to the position indicator of the slide valve; please contact the process cooling team. 18. Causes and solutions for the failure of the slide valve to be loaded/unloaded: 1. The solenoid coil is burned out and needs to be replaced. 2. Check whether the valves in the oil pressure system are open. 3. If the solenoid valve spool is rusted or the spring is broken, the spool needs to be replaced. 4. Check the main control board’s slide valve load/unload module and fuses. 19. Reasons for the failure of the slide valve loading/unloading function and methods to resolve it: 1. The solenoid coil is burned out and needs to be replaced. 2. There are foreign objects inside the solenoid valve spool, causing it to get stuck in one position and unable to move to either side. The valve core needs to be cleaned or replaced. 20. Causes and solutions for the failure where the slide valve (slider) cannot move: 1. The solenoid coil is burned out and needs to be replaced. 2. Check whether the oil pressure valve leading to the solenoid valve is open. 3. Manually simulate the operation of the valve spool; if the slide valve (slider) still does not function, it may indicate a mechanical fault in the compressor, please contact Work Cooling Hub. 21. Method for manually simulating the operation of a solenoid valve: The operation of a solenoid valve can be simulated manually as follows: Remove the coil of the solenoid valve and use a small iron rod with a diameter of 3/16 inch to push against the valve spool, allowing it to move a certain distance. If the loading/unloading mechanism moves, it indicates that the problem may lie in the electrical circuit. Conversely, there may be mechanical problems. 22. The oil level gauge in the oil separator shows an oil level, but the oil level in the tank is gradually dropping. Causes and solutions: 1. The oil level in the tank is too high. The excess refrigerant oil can be drained. 2. The compressor is carrying liquid or there is excessive liquid spraying, requiring adjustments to the system. 3. The suction superheat is insufficient; the evaporator supply flow needs to be adjusted. 4. The oil is contaminated, the oil filter is damaged or not in place; the refrigeration oil or oil filter needs to be replaced. 5. The oil return line of the oil separator is blocked and needs to be cleaned or replaced. 6. Clean the needle valve in the return oil line. 23. The oil level gauge in the oil separator shows no oil level, and the oil level in the tank is dropping rapidly. Causes and solutions: 1. During shutdown periods, the compressor’s suction valve does not seal properly; this valve needs to be repaired. 2. During the shutdown period, the bypass valve of the compressor’s suction valve is in the open position; this valve needs to be closed. 3. The oil filter screen is loose or detached; it needs to be tightened or reinstalled. 24. Causes and solutions for the failure to reach the oil pressure level required to start the compressor: 1. The filter of the pre-lubrication pump is clogged and needs to be replaced. 2. The check valve on the pre-lubrication line is leaking and needs to be replaced. 3. Inspect and clean the inlet filter of the pre-lubrication pump. 4. Check and verify the rotation direction of the pre-lubrication pump. 5. Check and open the inlet and outlet valves of the pre-lubrication pump. 6. Measure the oil pressure with a gauge to confirm that the reading of the pressure transmitter is accurate. 7. If the oil filter is clogged, check the pressure difference across the filter and replace the filter element as necessary. 8. The oil pump filter is clogged and needs to be cleaned. 9. The opening of the hydraulic pressure control valve is too large; adjust it to a smaller value in order to increase the hydraulic pressure. 25. Reasons for and solutions to the low oil pressure difference alarm that occurs when the compressor starts, due to a rapid drop in oil pressure: The opening degree of the main oil supply circuit valve is too large, or the opening degree of the oil pressure control valve is not appropriate. These two valves need to be adjusted appropriately. 26. Causes and solutions for oil pressure fluctuations: 1. The flow rate of liquid supplied through the spray tube is too high; it is necessary to readjust the opening degree of the manual valve on the spray tube circuit. 2. The refrigerant in liquid form is present in the cooling oil that enters the oil pump; it is necessary to check whether the oil temperature is too low. For newly started units, it is important to verify that components such as the oil heater are functioning properly. 27. Causes and solutions for grease leakage from the oil pump casing: Generally, under shutdown conditions, a slight amount of grease from the oil pump may leak. But once the oil pump is started, there should be no more leaks. If black grease is still leaking from the shaft end after the oil pump starts, it indicates that the oil pump’s seal is damaged and needs to be replaced. 28. Causes and solutions for high pressure difference across the filters in the main oil supply pipeline: 1. The oil filter elements are dirty and clogged; the elements need to be replaced. 2. Oil temperature is too low. Adjust the system to raise the oil temperature, and then check again. 3. The opening degree of the oil filter outlet service valve is too small; it needs to be fully opened. 29. Causes and solutions for abnormal vibration faults during unit operation: 1. The oil pump inlet filter is clogged, resulting in insufficient oil intake. The inlet filter needs to be cleaned or replaced as appropriate. 2. The liquid supply volume in the spraying pipeline is too high; it is necessary to adjust the opening degree of the spraying valve. 3. The oil pump is worn and needs to be replaced. 30. Causes and solutions for abnormal noises during unit operation: 1. Check whether the oil level is too low, and add oil as appropriate. 2. The oil pump is worn or damaged; repair or replace it. 3. The oil pump inlet filter has been damaged and needs to be replaced. 4. If the oil pump rotates in the reverse direction, the phase sequence needs to be adjusted. 5. The refrigeration oil is contaminated or the wrong grade of refrigeration oil is being used. 6. There is too much foam in the refrigerant oil; check the oil heater. 31. Causes and solutions for excessive oil temperature: 1. Insufficient liquid supply; it is necessary to check the liquid level in the reservoir as well as the pressure difference across the solenoid valve that controls the liquid flow. 2. The suction superheat is too high; the system needs to be adjusted. 3. The temperature sensing bulb of the thermal expansion valve on the liquid spraying pipeline is damaged and needs to be replaced. 4. The filter on the liquid spraying pipeline is clogged and needs to be cleaned or replaced as appropriate. 5. The coil of the liquid spraying solenoid valve is damaged and needs to be replaced. 6. The thermal expansion valve on the liquid spraying pipeline is too small and needs to be replaced. 7. The load is too high; it needs to be adjusted again. 32. Causes and solutions for low oil temperature fault: 1. The intake temperature is too low, and the degree of superheat of the intake air is insufficient; the system needs to be adjusted. 2. The compressor is carrying liquid, and the system needs to be adjusted. 3. The load is too low; it needs to be adjusted again. 4. The thermal expansion valve on the liquid spraying pipeline is too large and needs to be replaced. 33. Causes and solutions for oil temperature fluctuations: If the load on the entire system changes rapidly in a short period of time, it prevents the sensing devices located in the liquid injection pipeline from making timely adjustments. It is necessary to adjust the load of the entire system to bring it into stability. The above are the common faults and their causes of York screw compressors, compiled by Gonglenghui. Engineers should note that any inspections of the compressors are limited to analyzing or guessing the reasons behind the problems. Do not attempt to disassemble the compressor on your own if you are not completely sure. Blind disassembly can cause serious damage to the unit!