How to Test a Rectifier with a Multimeter (Guide)

A motorbike, ATV, or side-by-electrical side system comprises three parts: the battery, the stator, and the regulator/rectifier. If your device’s electrical system isn’t charging, one of those three components is most likely to blame. The only way to know which component is faulty is to test them all.

But how do you test a regulator/rectifier? A digital multimeter with a diode test mode is required to test a regulator/rectifier. If you don’t already have one, this is a fantastic time to obtain one.

In general, to test a rectifier with a digital multimeter, you must follow these steps. First, set the multimeter to measure resistance (Ω). Connect the cathode to the negative black lead and the positive red lead to the anode. The diode test is forward-biased in this setup, and you should receive a resistance value between 1 KΩ and 10 MΩ. Then, change the leads to the opposite ports. 

As we proceed, we will dig deeper into how to test a rectifier with a multimeter. 

What Exactly is a Rectifier?

A regulator/rectifier is electronic equipment that transforms the AC electrical current generated by the generator into DC electrical current and transmits it to the battery. The rectifier section of the regulator/rectifier unit is in charge of converting the current from alternating current to direct current. At the same time, the regulator portion is in charge of managing the amount of current supplied to the battery so that it does not harm it. (1)

A regulator/rectifier is made up of a series of diodes. A diode permits an electrical current to pass through it in one direction while preventing it from not moving to the opposite flow. The passage of electrical current via a diode is known as bias. Forward bias refers to the allowed direction of current flow, and reverse bias refers to the blocked direction of current flow. (2)

How to Test a Rectifier with a Multimeter

Confirm that a regulator/rectifier is operating correctly. You must test each of its diodes to ensure that they are appropriately forward biasing and reverse biasing. Regulator/rectifier units differ from one another and from one manufacturer to the next. Other regulators/rectifiers are more difficult to test than others, and some cannot be tested.

A regulator/rectifier has two electrical connections. These are typically a gray three-terminal connection for receiving current from the stator and a black two-terminal connector for sending current out to the battery. The positive is the inner terminal on the black two-terminal connection, while the negative is the outer terminal. Some regulator/rectifiers feature a black three-terminal connection with a ground terminal in the middle.

Note: Set your multimeter diode test mode when examining a regulator/rectifier.

Test 1: Forward Bias (Positive Circuit Diodes)

technician testing rectifier with multimeter
Video | dhiko mech

  • Connecting the multimeter’s negative leads to the positive terminal of the black two-terminal connection. 
  • Next, connect the positive lead of the multimeter to each of the three terminals of the gray three-terminal connection independently. 
  • The multimeter should read positive in volts. It indicates that each diode test allows electrical current to pass through (forward bias) and is thus operating correctly.

Test 2: Reverse Bias (Positive Circuit Diodes)

  • Connect the multimeter’s positive lead to the positive terminal of the black two-terminal connection. 
  • Next, connect the multimeter’s negative charge to each of the three terminals of the gray three-terminal connection. 
  • The multimeter should read “OL,” indicating that each circuit is open (OL stands for open-loop). It means that the diode prevents electrical current from flowing back through (reverse bias) and operating correctly.

Test 3: Forward Bias (Negative Circuit Diodes)

  • Connect the multimeter’s positive lead to the negative terminal of the black two-terminal connection. 
  • Next, connect the multimeter’s negative charge to each of the three terminals of the gray three-terminal connection. 
  • The multimeter should display positive volts, indicating that each diode permits electrical current to flow through it.
  •  If the forward bias test readings indicate voltage, the diode has failed, and you must change the regulator-rectifier component.

Test 4: Reverse Bias (Negative Circuit Diodes)

  • Connecting the multimeter’s negative leads to the negative terminal of the black two-terminal connection. 
  • Next, place the multimeter’s positive charge on each of the three terminals of the gray three-terminal connection. 
  • The multimeter should read “OL,” indicating that each circuit is open and the diode blocks electrical current from flowing back through.

Single Phase Rectifier vs. 3 Phase Rectifier

Single Phase Rectifier3 Phase Rectifier
Single-phase rectifiers have a single-phase AC power input. The structures are fundamental, using only one, two, or four diodes.3 phase rectifiers take three-phase AV power as an input. Structures require three or six diodes, one for each stage of the transformer secondary coil.
A single-phase rectifier converts using only a single phase of a transformer’s secondary coil, and diodes are linked to the secondary winding of a single-phase transformer. It results in a significant ripple factor.Three-phase rectifiers are utilized to lower the ripple factor instead of single-phase rectifiers. When employing extensive systems, three-phase rectifiers are favored over two-phase rectifiers.

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References
(1) generator – https://www.britannica.com/technology/electric-generator
(2) electrical current – https://www.britannica.com/science/electric-current

Video References

Rocky Mountain ATV MC

Dangar Marine

dhiko mech

About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gI realized early on carpentry was a huge passion for me and I’ve stayed in the industry for over 20 years now. This gives me a unique ability to really be able to tell you what the best tools and recommendations are. I’m not only a carpenter but I also like machinery and anything to do with electrics. One of my career paths starting off was as an apprentice electrician so I also have a lot of experience with electrical products and anything related.