Product knowledge

Fault Analysis of Some Main Refrigeration Accessories

Here are mainly listed pressure controllers, thermal relays, AC contactors, solenoid valves, high and low pressure controllers, differential oil pressure controllers, liquid level sensors and other refrigeration accessories failure analysis and the solutions.

#1. Fault Of Thermal Relay

  1. Common failures of thermal relays are:

  • The motor cannot start due to the contact failure;
  • The contact does not act when the compressor is overloaded;
  • When the compressor load is normal, the contact malfunctions, etc.
  • The motor cannot be started due to the failure of the contact;
  • The contact does not act when the compressor is overloaded;
  • When the compressor load is normal, the contact malfunctions, etc.
  1. The failure of the motor to start caused by the contact failure:

Generally, the contact is burnt out, the bimetal sheet is deformed, and the action mechanism is stuck.

  1. When the compressor is overloaded, the contact does not act:

Generally, it is caused by the setting value being too large, etc., the setting current should be reduced, and the dirt on the contact surface should be cleaned.

  1. When the compressor is normal, the contact malfunction fault:

Generally, if the setting value is too small, it will act without overloading. The set current value should be increased, or a suitable thermal relay should be replaced.

#2  Failure Of High And Low Pressure Controller

  1. The main reasons for the change of the set pressure are:

The spring is deformed, the bellows leaks or the connecting small tube is broken, and the micro switch shifts, etc.

  1. The high and low pressures are normal, but the reason for the failure of the controller is as follows:

After the high and low voltage control terminals are activated, the manual reset switch is not pressed, and when the pressure returns to normal, the contacts will not reset automatically. You can press the reset switch to reset the contacts; If it is too heavy to be repaired, it should be replaced with a new contact.

  1. High and low pressure exceeds the normal range and does not work Reasons:

The high and low pressure control contacts are stuck, the spring pressure is not adjusted properly, and the transmission rod is stuck; it may also be due to air leakage in the air cavity at the high pressure end. replace.


#3  Failure Of Oil Pressure Differential Controller

If it is caused by the failure of the adjustment spring, the electrical short circuit, the inaccurate pressure difference scale and the failure of the delay mechanism. The solution is to adjust or replace parts.

refrigeration accessories
bitzer two stage condensing unit

#4  Failure Of Solenoid Valve

  1. The valve does not act after power-on:

Use a multimeter to measure whether the supply voltage meets the requirements. Use a multimeter to measure whether the coil is open or blown. If it is open, it must be replaced with a new one.

  1. The valve core is stuck or rusted:

The main reason for being stuck by oil, such as the filter in the dry filter is broken, and the desiccant and dirt enter the solenoid valve and mix with the refrigerating machine oil to form a paste oil. For this kind of failure, you can carefully tap the valve body from bottom to top with a wooden stick when the solenoid valve is energized, and it can sometimes work. If the fault cannot be ruled out, it must be removed for cleaning.

  1. The solenoid valve is not tightly closed:

If the solenoid valve works for a long time, due to the wear of the valve core and valve seat, when there is a gap in the sealing part, it must be replaced with a new valve.

#5  Failure Of Liquid Level Sensor

  1. The liquid level change signal is sluggish or no signal is sent:

The reason is that the refrigerating machine oil enters the liquid balance pipe; the sealing performance of the wire bag chamber is not good, so that the wire bag is damp or corroded and damaged; the components in the electrical control box are out of order, etc. The treatment method is to remove the refrigerating machine oil in the pipe, repair the line package and control box, replace the components, etc.

  1. The level change signal is sent too frequently:

The specific reason is that the set upper and lower liquid level difference is too small; due to the violent evaporation of the refrigerant in the shell, the floating ball keeps beating, which leads to false signals. The treatment method is to adjust the liquid level and eliminate the gas.

#6  Failure Of AC Contactor

  1. The contactor does not pull in after power on:

Check the electromagnetic coil, measure the two ends of the coil with a multimeter, if the resistance is zero, it is a short circuit, if the resistance is infinite, it is an open circuit, and both need to be replaced. If the contact action fails or is stuck by other components, it should be carefully adjusted to remove obstacles. If the armature is stuck and cannot be lifted, it should be removed and repaired in time.

  1. The contactor does not disconnect after the power is turned off:

The contacts of the contactor are stuck, check carefully to eliminate the sticking fault, repair or replace the contacts; if there is oil or dust on the surface of the contactor iron core, the surface of the iron core should be cleaned to make it smooth, but not too smooth to prevent delayed release ; The mechanical part of the contactor is stuck, and the stuck phenomenon should be eliminated; the reaction force of the return spring is too small, and the spring should be adjusted or replaced.

  1. Excessive vibration or noise during operation:

There are many reasons, among them, when the end faces of the dynamic and static iron cores are in poor contact, try to repair them; if the contacts are oxidized, uneven, and burr, use fine sandpaper and files to repair them; if the contacts are burnt, replace them with new ones. , and check the cause of the burning; the vibration and noise caused by the excessive spring reaction force should be replaced with a suitable spring.

  1. The action of the contactor is slow when the coil voltage is insufficient:

The coil voltage should be adjusted; when the reaction force of the return spring is too large, a suitable spring should be replaced; when the gap between the moving and static iron cores is too large, the gap can be adjusted to be small.

  1. When the contact is working, it will ignite and vibrate when the iron core is closed:

The coil voltage can be adjusted to make it work normally; when the short-circuit ring is damaged, it should be replaced with a new one; due to frequent operations and contact deformation resulting in poor contact or insufficient contact force, the burnt-out contact should be smoothed with fine sandpaper. Adjust or replace the spring and readjust the contact gap.

  1. The contacts are seriously overheated when the load current is too large:

The cause of overload should be found out and measures should be taken; when the contacts have oxides or severe burns, resulting in shrinkage of the contact surface and poor contact, repair with a file or sandpaper.


You can check the conditions of the above accessories and take countermeasures to solve the problem of refrigeration accessories failure so that the refrigeration equipment can work well. For more, you could contact us.