How to check the engine with a multimeter? (3 way guide)
Content
A bad motor can cause a lot of problems. This way you never know when you might need to check your engine. That is why today we will look at how to check the engine with a multimeter. However, for this process, you will need some DIY skills. With some DIY skills and proper execution, you can complete the task quite easily.
In general, to test the motor, you first need to put the multimeter in resistance mode. Then check the motor terminals and wires. The goal is to test the windings for an open or short circuit.
In addition to the method described above, there are two other methods by which we can test the electric motor. Here we are going to discuss all three motor tests. So let's get started.
Test 1: Compare the voltage across the capacitor terminals with the applied voltage
When properly connected, the voltage at the capacitor terminal should be 1.7 times the voltage of the power supply. If you are getting readings according to the ratio mentioned above, that means the motor is getting the correct voltage. For this motor test, we will use two multimeters; Circuit tester A and circuit tester B.
Step 1: Check the power supply voltage with a circuit tester A.
As in the diagram above, first connect the red test lead to the red wire; connect the black probe to the black wire. This is the process for circuit tester A. The multimeter must be in AC voltage mode. Before connecting the multimeter to the motor, you must make the necessary settings for the multimeter. If you follow these steps correctly, then you should get the voltage of the power supply. If you are using a 100V AC motor, you will get 100V on the multimeter.
Step 2: Check the voltage at the capacitor terminals using a circuit tester B.
Now use Circuit Tester B to check the voltage across the capacitor terminals. Connect the red probe to the red wire. Then connect the black probe to the white wire. Now check the voltage with a multimeter. If all connections are good, you will get a reading of 1.7 times the power supply reading.
For example, if you are using a 100V motor for this test, the multimeter will read 170V.
When you get a reading of 1.7 times the power supply capacity, it means the motor is running normally. However, if you are not getting this reading, the problem may be with your engine.
Test 2: check the electricity that is carried through the cable
Any type of faulty wires or connectors can be the cause of an engine malfunction. Therefore, it is always best to check the wires and connections before drawing any conclusions. With this method, we are going to check if the motor circuit is open or short with a simple continuity test.
Step 1 - Turn off the power
First, turn off the power. Power is not required when performing a continuity test.
Step 2 - Make the connections according to the diagram
Check the diagram above and connect the C and D circuit tester respectively. To do this, you need to connect the red lead C to the black wire and the red lead D to the red wire. Now connect the remaining two black probes C and D to the end of the extension cable. If there are any breaks on the circuit under test, the multimeters will start beeping.
Note: When checking wires, always select an open area near the engine. When connecting sensors to wires, make sure they are connected correctly.
Test 3: Motor winding resistance test
In this test, we are going to measure the motor winding resistance. We will then compare it with the originally calculated motor winding values. After that, we can check the condition of the engine by two values.
Step 1 - Remove all optional components
First, remove additional components from the motor circuit, such as capacitors and extension cords.
Step 2 - Set up your multimeter
Now set your multimeters to resistance mode. If you remember, in the previous two tests we set the multimeters to voltage mode. But not here.
Step 3 - Connect the sensors
Connect both black test leads to the black wire. Now connect the red lead of circuit tester E to the red wire. Then connect the red lead of the F circuit tester to the white wire. If you are still confused, study the diagram shown above. (1)
Step 4 - Check and Compare Readings
The multimeter reading should be 170 ohms, given that if we use a 100 volt motor. Sometimes these readings can be less than 170 ohms, for example, with an internal short circuit, the readings can be less than 170 ohms. However, if the windings are damaged, the reading should be more than a few thousand ohms.
In the example above, we used a 100V motor. But when it comes to other motors, you will have to know the calculated values depending on the model. Try searching online or ask the manufacturer. Then compare the two values. (2)
What should I do if the engine fails the above tests?
If your engine fails these tests, then something is wrong with it. The reason for this issue could be a bad motor or faulty components such as; bad relays, switches, cables or wrong voltage. Whatever the reason, you have a faulty motor.
However, depending on each test, the solutions may differ. For example, if the motor fails the 1st test, the problem is in the wiring or capacitors. On the other hand, if the motor fails the 2nd test, the problem is in the connector or cable. For a good understanding, here is a simple guide.
If the engine fails Test 1You may need to replace the wiring and capacitors.
If the engine fails Test 2you may need to replace the connector and cable.
If the engine fails Test 03you may need to replace the motor.
Mechanical problems such as a failed ball bearing can disrupt your engine. This situation occurs due to excessive axial or radial load. You may also need to check for these kinds of problems. So, follow these steps.
Step 1: First, remove the gearbox and motor.
Step 2: Then turn the shaft clockwise and counterclockwise.
Step 3: If you hear abnormal friction or sound as the shaft rotates, this is an indication of misalignment or damage. In this case, you may need to replace the motor.
Summing up
These three methods are the best solutions for testing electric motors. If you follow these steps correctly, you can determine the condition of any engine. However, if you still have any doubts, feel free to review the article again.
Take a look at some of our articles below.
- How to test a fan motor with a multimeter
- How to read an analog multimeter
- Overview of the Power Probe multimeter
Recommendations
(1) diagram – https://www.computerhope.com/jargon/d/diagram.htm
(2) Internet – https://www.livescience.com/20727-internet-history.html
