# How To Check The Motor Winding

## Video: How To Check The Motor Winding

Electric motors on a car can perform a wide variety of functions. They operate the windscreen wipers and power windows, open the sunroof, and allow centrally controlled locks to operate. If the electric motor stops working, then perhaps the reason lies in the violation of the integrity of its winding. There are special techniques and devices for checking the winding.

## Instructions

### Step 1

Using a megohmmeter, check the insulation resistance of the motor windings between the frame and phases. To do this, first remove the jumpers on the motor terminal block (they can be made in the "star" or "delta" type). Check the terminal block by shorting it to the housing and between the terminal connection fixing bolts.

### Step 2

On a wound rotor motor, visually check the insulation of the brush holders and slip rings.

### Step 3

Check motors with rated voltage less than 127V with a 500V megohmmeter. If the rated voltage is higher, a 1000V megohmmeter is required.

### Step 4

If, according to the results of checking the winding relative to the body and between the phases, the measurement results differ significantly, the motor must be repaired or replaced. Most likely, it works in two phases. The motor should be considered defective if the insulation resistance of the winding is less than 1MΩ.

### Step 5

To check possible turn-to-turn short circuits, use special equipment, since a conventional ohmmeter, even a digital one, will show the difference between the windings only when a short circuit in the turns is obvious and already visible to the eye.

### Step 6

To measure a low resistance winding, run a DC current from the battery through it. Using the adjusting rheostat, set the current from 0.5-3.0A. After setting the current and until the end of the measurements, do not change the position of the rheostat.

### Step 7

Now measure the voltage and current drops, and then calculate the winding resistance using the formula R = U / I (where R is resistance, U is voltage, and I is current). The winding resistance should not differ by more than 3%. This method is also suitable for checking a collector motor.

### Step 8

In some cases, it is possible to determine that a three-phase motor operates in two phases by visual inspection. A sign of a malfunction will be darkening in the "frontal" part of only those coils on which there was voltage.