How To Test A Rectifier On A Motorcycle

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How To Test A Rectifier On A Motorcycle – Here’s a quick (but comprehensive) guide on how to test the motorcycle charging system on any motorcycle – whether you’re buying one, or own one.

The charging system for a motorcycle is actually quite simple. Diagnosing faults will be easier if you know how a motorcycle charging system works and what can go wrong with it.

How To Test A Rectifier On A Motorcycle

How To Test A Rectifier On A Motorcycle

And since mistakes are not common, knowing how to fix a charging system can mean the difference between getting 200km home or being stranded in the middle of nowhere.

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It could also mean avoiding buying junk, or offering $500 off the asking price of a motorcycle.

I’m good That’s why I created this site – as an outlet. I love learning and sharing what others find useful. If you like what you read here, and are as passionate as I am, you will want to know when I will be publishing more. (Check the latest for an idea of ​​what you’ll see.)

In essence, a motorcycle’s charging system consists of only five major electrical components (which often fail).

If something is malfunctioning in your motorcycle’s charging system, it is one of the parts that has failed. Identifying who is failing is the important part. Rectifier, Motorcycle Voltage Rectifier Regulator Heat Sink Fin Metal Replacement For Cb400n Cb250n Ft500 Cb450n Ch125

Many times, when you ask about motorcycle charging systems in forums, people say “dead battery” and give examples of when they bought the battery and it died from the store. I’m sure it will happen and sometimes they will be right. But don’t buy the battery unless you’re sure it’s the cause. Better yet, if it’s dead, find out who killed it. Better not to just “throw spaghetti at the wall”. Spaghetti is a waste.

The big change I see in modern motorcycles is that sometimes the stator coil is not directly driven from the engine, and is instead in a separate unit (the alternator) that is driven by a belt, like in a car. I saw this most recently on the BMW R1200* engines, and I wrote a guide to changing an alternator belt.

There are several key symptoms of a bad motorcycle charging system. Either of these could mean something is broken in your charging system.

How To Test A Rectifier On A Motorcycle

Basically, if your motorcycle does not charge (or it stops), it means that one of the above components has failed!

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Failure of a component in a motorcycle charging system can happen in a number of different, all common, ways:

Other than that, all you need are regular tools, like those in your toolkit. You need to remove the battery and unplug a few things. I’m just saying you should

Before doing any testing on your motorcycle charging system… you should use a trickle charger that you purchased from Amazon or eBay. Leave it on overnight.

You must charge your battery before performing any other test, otherwise your results will not be meaningful.

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You usually have to remove the seat and fairing, if you have one, to charge your battery. Sometimes you have to remove the tank — I pray it’s not you!

Mental note: I’m so thankful I have a motorcycle with a fairing (to keep me warm) but this bikini fairing so I can access everything.

Once your battery is charged, you’re ready to start testing your motorcycle charging system! Test the battery voltage with your multimeter.

How To Test A Rectifier On A Motorcycle

Before you buy a new battery — If your bike is working normally and you suddenly need a new battery … you should ask yourself: “Why is my battery dead? “

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If it is old—say, the battery has never been replaced, or it is more than 5 years old—you may feel comfortable replacing the battery.

But if a bad regulator / rectifier fries it, you just fry a new one, wasting your time and money. Testing reg/rec — we’ll do that next.

Now start the motorcycle, warm it up a bit, and check the battery voltage again.

Is the voltage below 12V at idle? Then there is something that does not produce enough current. You may have too much current coming through your system somewhere, you may have a faulty alternator/stator coil, or your reg/rec may have completely failed.

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Is the voltage above 15V at 3,000 rpm? If so, your regulator/rectifier may be partially fried. You can do more testing with this (that’s a story for another day). But you can take it, or take a pot-shot and buy one and replace it. Worst case, you need that extra later (they all die eventually).

For a more in-depth look at what part of your motorcycle charging system isn’t working, see if your alternator/stator coil is working, or if your reg/rec is working.

Removed the stator coil from my old Ducati Monster 900. I was pretty sure this was the problem before going to this length!

How To Test A Rectifier On A Motorcycle

You need to know if your alternator / stator coil is producing enough power. You can usually see if it is by testing the output voltage.

Regulator/rectifier Diode Inspection

A stator coil is a coil (or a series of coils) that sits around the rotor. The rotor is simply a magnet attached to the crankshaft of a motorcycle.

When a motorcycle’s engine turns—that is, when it’s turned on (or when you push it!)—the rotor magnets turn. Magnets rotate inside the stator coils. The changing magnetic field caused by the turning of the magnet induces a current in the coil. It works opposite to an electric motor.

To test your stator coil, you need to check if it is producing enough voltage. If so, that’s usually a sign that it might be charging. (Not necessarily, but almost always.)

First, find the output of your stator coil. Usually a plug comes out of the whole place.

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Don’t know where the output of the stator coil is? On longitudinally mounted engines, such as V-twins, you usually find the clutch on one side of the engine and the stator on the other. You know about the clutch because the clutch cable and actuator go into it. You know about the stator because it’s on the other side! On that side, you can find the plug.

On a transversely mounted engine like my BMW or many inline-four motorcycles, it’s less obvious. There, it’s easy to find the regulator/rectifier (under the seat, always) and check the voltage there.

If you still can’t find a problem, you can do some tests to run the engine. You have already charged the battery, so it should be on.

How To Test A Rectifier On A Motorcycle

Now you can test the voltage between the stator coil terminals at 3,000 rpm. Depending on your motorcycle, you should get a reading of anywhere between 20 and 50 volts.

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What voltage you get is not important (as long as it is less than 15 – at 3,000 rpm, there should be enough voltage to charge the battery, ie more than 15). What is more important is that a) all terminals have voltage readings and b) they are all the same (if you have a multi-phase alternator).

Some older alternators only have two phases and only have two output wires. With them, that’s the only voltage you measure.

Most modern alternators have three phases and three output wires. So you need to measure A-B, B-C and A-C. In this case, your voltages should be the same.

It often fails on older motorcycles because they have lived rough lives. For millions of engine revolutions, they need to get a huge voltage, convert it to DC, then cut off the excess, bleed it to heat.

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This is what regulators/rectifiers do (they’re actually two things, but they’re usually in one unit because it’s easier to do it that way – they’re made with high current diodes).

The rectifier converts the AC voltage to DC. It’s just like any other power adapter in your home, like for your phone charger. The AC voltage that comes out of the wall socket needs to be converted to DC to charge your devices. AC can only be used in things that only provide heat or light (where the direction of current is not important), such as ovens, toasters, kettles, and lamps.

A “full-wave” rectifier circuit. It doesn’t matter if the AC swing is up or down, it produces a positive voltage.

How To Test A Rectifier On A Motorcycle

The regulator brings the voltage down from high to a level where it won’t fry your battery. The alternator produces a large voltage – the more your engine revs. The regulator cuts the excess and gives your battery only what it needs. Sometimes, it reduces 70% of the available voltage!

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The sad thing about it is that it gives off all that extra power like heat. That’s why the regulators will fry. They were overwhelmed.

If a regulator is fried, you get a) no voltage (flat battery) or b) too much voltage (fried battery, which also means flat battery).

So if your battery is dead and you replace it without checking your reg/Rec, you can fry the battery again.

To test the regulator/rectifier: good, if you

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