Motorcycle 12 Volt Electrical System Basics & Troubleshooting – part 2 - Testing & Troubleshooting

Motorcycle 12 Volt Electrical System Basics & Troubleshooting – part 2 - Testing & Troubleshooting

Tips for testing and troubleshooting motorcycle electrical systems

Time for part 2 of our series on motorcycle 12 volt electrical systems.  In this article we’ll pick up where we left off in the previous article discussing 12 volt electrical system basics and take a look at electrical system trouble shooting approaches for your bike.

Before getting into this discussion, we need to mention a couple of important safety tips. Even though a motorcycle electrical system is rated at 12 volts, there can be enough amps in the system to give you a nasty shock. Always wear shoes with some type of insulating material.  Don’t work in an area that is wet.

If the battery is connected, do not simply grab or touch a naked wire, or terminal. Be particularly careful if you are handling the spark plugs. These operate at high voltages and they should be disconnected completely before handling.

Now that we have gotten that out of the way, you will need a couple of things to get started. First you need a wiring diagram for your bike  This may be in your owner’s manual or you may need a shop manual  Then you need something to test circuits.  The simplest tool you can have is a testing bulb. This is a 12-volt bulb with two leads ending in a terminal each.

However, you more than likely will want a digital multimeter.  Check out this one on UTZStore.com.  A multimeter will let you check voltage, continuity and many other functions.  Let us look at how we can troubleshoot the various electrical components based on the symptom you are having.

Symptom: Your battery is weak or completely discharged
If your battery is weak or completely discharged, this typically happens for one of three reasons. Either the battery is faulty, there is an issue with the charging system, or the wiring is faulty.

Check your battery
With the motorcycle turned off, check the battery. If you are using the bulb method, just touch the terminals of the bulb to the battery. If the bulb glows at full intensity without flickering, the battery is fine. If using the multimeter, set it to DC voltage and measure the voltage. If the battery is fully charged it should give a reading that is 12 volts or higher with no load on it.  Otherwise, if the battery shows a lower voltage say 10.5, you may have a shorted cell.  If no voltage then the battery is dead.  Try to charge it (insert link for UTZ Smart Charge) and see whether it is still viable. If not, you may need a new battery.  If it holds a charge, then continue trouble shooting.

You should then test your battery under load.  With your bike running, check the voltage at the battery terminals.  You are looking for a couple of issues.  If the voltage reads below 10.8 volts while under load, the battery may no longer be viable.  You are also checking t see whether the battery is getting overcharged.  If everything in the charging system is working properly it should bring the battery voltage up to a range of 14.2 to 14.8 volts.  If you are getting a reading higher than that your system is possibly overcharging.  Under that and it may not be able to keep up.  Both situations need to be checked further.

If the the battery checks out OK, then troubleshooting the charging system is next.

Symptom:  Your battery holds a charge but runs down while you are riding
If you can charge your battery fully with an auxiliary charger but it won’t hold a charge while operating your bike, that’s a sign you need to check your charging system. 

Check your charging system
First check your wiring running between the battery and the rectifier/regulator. Use your multimeter, to check it. Set the multimeter to the continuity test and connect the terminals to each end of the wires. If there is a break or a short somewhere along the way, the multimeter will let you know.  Repair or replace the wire and see if this resolves the issue.

Next check the stator as that is where the AC current comes from. If it isn’t functioning properly the battery will drain while you are riding from the load of every accessory that needs power. To troubleshoot the stator, first disconnect the connector that runs to the engine. You can then test it with your multimeter.

You want to check the tabs of the connector for continuity.  Use your multimeter to check this. Check the A to B, B to C and then A to C tabs and look for a reading under 1 Ohm. If you get a reading over 1.5 Ohms then you may have a bad stator.

Next you want to check the rectifier/regulator.  To test your rectifier/regulator you need to set your multimeter to its diode function.   Disconnect the positive(red) and negative(black) leads along with the stator leads (typically yellow).  You are going to check both the positive and negative lead for each stator input lead for forward and reverse bias (direction of current flow). 

Connect the positive multimeter lead to the red rectifier lead. Then connect the negative multimeter lead to each stator input.  There should be no reading.  Reverse this and connect the black multimeter lead to the red rectifier lead.  Touch the red multimeter lead to each stator input lead. You should get a reading with each one. (the number doesn’t matter).  You need to then test the negative lead which is the reverse of the positive lead. You should get no reading then readings for the opposite bias.

Symptom: An electrical component like your lights or a horn is not working
In many cases, motorcycles will have some type of a relay for each of the electrical components.  A relay acts as a switch to the accessory. Refer to your  manual to figure out where these are located on your bike.

Relays are generally interchangeable (insert link to UTZ Store relay). So, switch the relay for the device in question with the relay from a device that is working. If this fixes the issue then you need to replace the relay.

Otherwise you might have to check the entire length of  both the power wire and the ground wire connected to the device. Ground faults are a frequent cause of problems and also a quick fix. So this is something you want to check and eliminate early in any trouble shooting.

Again, reach for your multimeter. Using either the continuity test or resistance test you can figure out if there are any breaks in the wire. If there is a break, you will need to replace or repair the wire.  A quick and temporary repair can be as simple as cutting, stripping and connecting the two ends then covering bare wire with shrink wrap or electrical tape. In the long run though you will want to run a new wire.  Also check your connections at both end of the wire.  A loose connection is an easy fix.

We hope you found this helpful.  Thanks for reading and get out and ride!

Your friends at UTZStore.com

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