How To Determine The Cause Of Your Charging Problem

I'm no stranger to tracking down electrical issues.  My first bike, the VX800, developed a charging problem within three days of bringing it home.  It turned out to be a bad rectifier, and replacing it was an absolute nightmare of back-ordered parts, and then contending with getting the old rectifier off the bike.  Suzuki, in their infinite wisdom, located it on the back of the motor, just in front of the exhaust crossover tube.  And the bolts holding it in place, for no understandable reason, had stripped Philips heads.

I'm still recovering from the trauma of that repair.

So now the Triumph is having charging issues.  Here's a quick guide on how to go about figuring out the cause of the problem if you've got a bike with a stator and regulator/rectifier (You probably do.  If you're not sure, find out before proceeding.).  In yesterday's post, I mentioned the value of a multimeter.  Have you got one yet?  You're going to need it, so go get one.  I'll wait until you get back.

Step One: check your fuses.  It's probably not a bad fuse, but it would be embarrassing to pull everything apart only to find the problem was a fuse.

Step Two: Set your multimeter to test DC voltages.  I'd set it to at least 20 volts.  Start your bike, and put the red probe on the positive battery terminal, and the black probe on the negative battery terminal.  Rev the motor to 2500 RPM.  If the voltage is less than 13.5 volts, there's a problem.  If it's higher than 13.5 volts, rev the motor to 5000 RPM. If the voltage is more than 14.8 volts, there's a problem.  Go ahead and shut off your bike for now.

In my case, the voltage was about 12.5, and didn't change at all when I revved the motor.  At this point, I guessed the stator was bad, but it's best to be sure, so I continued on.

Step Three: Pull all the plastics and other parts off your bike keeping you from the connectors for the stator and regulator/rectifier (RR).  On the VX800, the connectors were hidden under the gas tank and were a real drag to get to.  On the other hand, the connectors were super easy to get to on the Speed Four, just tucked under the rear plastic on the chain side of the bike.

Disconnect the RR from the stator and battery.

If you don't know what a RR looks like, it's the finned, octagonal hunk of aluminum with wires coming out of it in the photo to the left. 

Step Four: Set your meter to read resistance.  Test from each of the three yellow wires coming from the RR to each of the red / black wires.  If one of the readings indicates a short (zero resistance), you need a new rectifier.

The rectifier on the Triumph is fine.

Step Five: Check the resistance between all combinations of the three yellow wires coming from the Stator.  It should be a very low resistance, probably less than 1 ohm, but it should absolutely not be a short circuit.  Also check from one of the yellow wires to engine ground.  This should read maximum resistance (an open circuit).  Again, if you've got a short, the stator is bad.

My stator appeared good here.

Step Six: Leave the stator and RR disconnected.  Set your meter to read AC voltage.  Start the bike, and check the voltage coming from all combinations of the three stator wires.  The three voltages should all be the same.  If one is significantly different, your stator is bad.  At idle, you can expect the voltage to be around 20 volts, and it should go up to about 70 volts at 5000 RPM.  These voltages can, of course, vary depending on the bike.

On the Triumph, at idle, the voltages read 24, 24, 4.  Bad stator.  The good news is, the stator on the Speed Four looks exceptionally easy to replace.

So now for the fun part:  The OEM stator for the Speed Four runs about $600, and there appears to only be one company making aftermarket replacement stators for my bike right now.  Hopefully, this one company will prove easy to work with.

If you followed the previous steps, found nothing, and are still having trouble, chances are you've got a bad connection somewhere.  I am not jealous of you.

For a really, really thorough troubleshooting guide, check out this fault-finding chart provided by Electrosport.

I also found this thread provided by the Triumph Rat forum most helpful.