For systems in which the diving cooler pump is a three-phase motor, measurements are made under unbalanced conditions. It can measure any two of the three-phase lines with the smaller resistance block of a single multimeter and compare them separately. If it is found that the resistance values of the two groups differ greatly, it can be judged that the three-phase is unbalanced.

When the motor is running, the voltage range of the AC motor can measure two lines. If the voltage unbalance rate is higher than ten percent, you need to check whether there is a voltage drop on the line. If there is no voltage drop on the line, there is a problem with the motor. You can find clamp meters to measure if the three phase currents are balanced. If it's out of balance, the motor needs a major overhaul.

Whether it is a single-phase or three-phase motor, if the coil is grounded and the insulation is damaged, you can use a multimeter to measure the distance between the coil and the housing to see if it is infinite, otherwise the diving cooler pump will be burned out.