Measure the Resistance of a Refrigerator's Complete Circuit with a Multimeter
The fault detection of refrigerators can be carried out through inspection, listening to sound, touch, instrument measurement, etc. In fact, the power supply is supplied during the maintenance process. Based on some fault phenomena, we can use some simple instruments to detect and further determine the location of the fault.
For example, using a multimeter to check the resistance of the circuit of the entire refrigerator (from both ends of the power plug), in order to determine the location of the fault.
1. Method for Measuring the Resistance of Direct Cooling Refrigerators
Unplug the power plug of the refrigerator and measure the resistance between the live wire (L) and the neutral wire (N): when the refrigerator door is closed, the normal value is 7-20Q Ω; when the refrigerator door is open, its resistance should be greater than 7-20 Ω. If the measured resistance value is ∞, it indicates that the circuit is in a disconnected state, and the temperature controller, overload protector, compressor motor, or lamp holder and bulb must be checked. If the measured resistance is 0 Ω, it indicates a short circuit in the circuit. At this time, do not turn on the compressor motor and light bulb.
Measure the resistance between the live wire, neutral wire, and ground wire (E): The normal resistance value is infinite. If the resistance value is 0 Ω, it indicates a short circuit phenomenon; If the resistance value is below 2M Ω, it indicates poor insulation of the refrigerator, and the circuit, compressor, thermostat, light bulb and other related components need to be checked.
2. Detecting operating current with a clamp ammeter
(1) Use a clamp ammeter to measure the operating current. If the measured operating current is greater than the rated current on the nameplate, the following faults may occur:
① The refrigeration pipeline is blocked, and there is air entering the system.
② Poor lubrication of the compressor, resulting in cylinder jamming or shaft holding. Partial surface or insulation reduction of compressor motor winding.
③ Excessive refrigerant charging during maintenance caused an increase in compressor load.
(2) If the measured current is lower than the rated current on the nameplate, the following faults may occur:
① Insufficient or leaking refrigerant reduces the load on the compressor.
② The efficiency of the compressor decreases due to reasons such as damaged cylinder gaskets, collusion between high and low pressure chambers, poor sealing of the steam valve, and excessive wear of the piston and cylinder.
