How to Test a Stator with a Multimeter (3-Way Testing Guide)
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The alternator, consisting of a stator and rotor, powers the engine by converting mechanical energy into electricity and also charges the battery. That's why, if something goes wrong with the stator or rotor, your car will have problems even if the battery is fine.
Although the rotor is reliable, it is relatively more prone to failure because it contains stator coils and wiring. Therefore, checking the stator with a good multimeter is an essential step in troubleshooting alternators.
The following steps will help you test the stator with a digital multimeter.
How to check the stator with a multimeter?
If you're having trouble charging your car or motorcycle, it's time to take out your DMM.
First, set the DMM to ohms. Moreover, when you touch the meter wires, the screen should display 0 ohms. After preparing the DMM, test the battery with the meter leads.
If the DMM reads around 12.6V, your battery is good and the problem is most likely with the stator coil or stator wire. (1)
There are three ways to test stators:
1. Stator static test
A static test is recommended if you are having trouble charging your car or motorcycle. Also, this is the only test you can run when your car won't start. You can either remove the stator from the car engine or test it in the engine itself. But before checking the resistance values and checking for a short in the stator wires, make sure the motor is off. (2)
In a static stator test, the following steps are performed:
(a) Turn off the engine
To check the stators in static mode, the engine must be turned off. As stated earlier, if the vehicle won't start, the stator static test is the only way to test the stators.
(b) Set up the multimeter
Set the multimeter to DC. Insert the black lead of the multimeter into the black COM jack, which means Common. The red wire will go into the red slot with the symbols "V" and "Ω". Make sure the red wire is not plugged into the Ampere connector. It should only be in the Volts/Resistance slot.
Now, to test for continuity, turn the DMM knob and set it to the beep symbol as you will hear a beep to make sure everything is okay with the circuit. If you have never used a multimeter before, please read its user manual before using it.
(c) Run a static test
To check continuity, insert both multimeter probes into the stator sockets. If you hear a beep, the circuit is good.
If you have a three-phase stator, you need to perform this test three times, inserting the multimeter probes into phase 1 and phase 2, phase 2 and phase 3, and then phase 3 and phase 1. If the stator is OK, you should hear a beep in all cases.
The next step is to check for a short inside the stator. Remove one wire from the stator socket and touch the stator coil, ground or vehicle chassis. If there is no sound signal, then there is no short circuit in the stator.
Now, to check the resistance values, set the DMM knob to the Ω symbol. Insert the multimeter leads into the stator sockets. The reading should be between 0.2 ohms and 0.5 ohms. If the reading is out of this range or is equal to infinity, this is a clear sign of a stator failure.
We advise you to read your vehicle's service manual to know the safe readings.
2. Stator dynamic test
The dynamic stator test is performed directly on the vehicle and supports the multimeter in AC mode. This tests the rotor, which contains magnets and rotates around the stator. To perform a dynamic stator test, the following steps are performed:
(a) Turn off the ignition
Following the same procedure as for the static test, insert the multimeter leads into the stator sockets. If the stator is three-phase, this test must be performed three times by inserting the probes into the sockets of phase 1 and phase 2, phase 2 and phase 3, phase 3 and phase 1. With the ignition off, you should not take any readings when performing this test.
(b) Ignition with ignition switch
Start the engine and repeat the above ignition for each pair of phases. The multimeter should show a reading of about 25V.
If the readings for any pair of phases are extremely low, say around 4-5V, that means there is a problem with one of the phases and it's time to replace the stator.
(c) Increase engine speed
Revise the engine, increase the rpm to about 3000 and retest. This time the multimeter should show a value of about 60 V, and it will increase along with the number of revolutions. If the reading is below 60V, the problem is with the rotor.
(d) Regulator rectifier test
The regulator keeps the voltage generated by the stator below a safe limit. Connect your car's stator to the regulator and set the DMM to check the amps on the lowest scale. Turn on the ignition and all igniters and disconnect the negative battery cable.
Connect the DMM leads in series between the negative pole of the battery and the negative pole. If all previous tests were OK, but the multimeter reads less than 4 amps during this test, the regulator rectifier is faulty.
3. Visual inspection
Static and dynamic are two ways to test stators. But, if you see obvious signs of damage to the stator, for example if it looks burnt out, this is a clear sign of a bad stator. And you don't need a multimeter for this.
Before you go, you can check out the other tutorials below. Until our next article!
- How to test a capacitor with a multimeter
- Cen-Tech 7-Function Digital Multimeter Overview
- digital multimeter TRMS-6000 overview
Recommendations
(1) Ohm – https://www.britannica.com/science/ohm
(2) car engine - https://auto.howstuffworks.com/engine.htm
