Replaced battery on my 1990 FXRS about 2 months ago. Been riding almost everyday, plugging into battery tender at end of day. No issues starting each day.

Went for weekend campout on my FXRS (with no access to daily tender-ing). After full day of riding with lunch and gas stops, began to have starting issues. Behavior (the infamous single click) was like a bad starter relay. Replaced with new starter relay I had with me. Bike started.

At next stop, bike would not start. Decided to try jumping it with my son's bike. My FXRS fired right up. Spent the next 6 hours riding home, keeping bike running at gas stops.

When I got home, I thru a voltmeter on the battery and I'm only holding 9 volts. Additionally, my turn signals and horn no longer work. Headlamp is dim, but operational. Brake lights seems OK.

I believe to check the stator, I need to verify the voltage output around 35 volts for around 2,000 RPMs. Also, the resistance on the connectors should be low, but not zero.

If the stator passes these tests, is my regulator shot? Are there an easy way to test the regulator? What other tests should I perform? And is my turn signals and horn related to my starting issue?

Sorry for deep ending on details, but I thought they might be important.

Thanks for your help.

 

Dr.Hess' How To Diagnose Your Charging System
Buy about a $10-20 digital multi meter. Fully charge the battery (overnight on a 1 amp charger).

Scale on DC Volts, around 20V max voltage scale. Nominal readings are given in brackets. Check voltage across battery terminals (12.8). Turn bike on. Check voltage (less than previous, ~12.0+, depending on headlight, accessories). Start bike and let idle. Check voltage (could be 12.0 to 15). Rev to about 2500. Check voltage (should be more than observed with bike on but motor not running, and more than with bike off. Ideally between 13 and 15.) Turn high beam on. Should be about the same, give or take a little. If the voltage is over 15 or 15.5-ish with a headlight on, I'd consider replacing the regulator and/or checking all grounds (battery to frame, regulator to frame in particular).
If you pass the above tests, your system is most likely fine, including the regulator and stator. If you don't pass, then:
Bike off. Meter set on Ohms, medium-ish scale, like 20K or 200K Ohms max scale. Pull stator plug. Ground the meter black lead to a good chassis ground, like a bolt or even the battery negative. With the red lead, touch a different part of the bike, like the engine case at an unpainted part or another bolt. Meter should read low ohms, like 0. With the red lead, touch each contact on the motor side (stator) of the plug (the part stuck in the case). Depending on if your case has a male or female plug, if you can't see the metal part/pin of the plug, you can put a paper clip in the hole and touch the paperclip with your meter red. Meter reading should be infinity on all pins. If it isn't, your stator is shorted to the case, replace.
The following is for single phase systems. I don't have a multi-phase and haven't had to diagnose anyone elses, so I haven't dug into those systems.
Set meter to lowest ohm scale, like 200, typicaly. Check resistance between the two stator plug pins. Should be fairly low, like a few ohms. The spec is in your shop manual. If it is infinity, stator is blown open. If it is 0, stator is shorted to itself.
Set meter to AC Volts, 100V scale. Attach each meter lead to a stator pin. You may need to rig up some type of temporary plug. It is important that nothing can short to ground or to each other accidentally, or you will blow the stator if it wasn't blown before. An old plug off of your last regulator is a good way to do it, but, get creative and be careful. I can do it holidng the leads on the pins once the bike is running, but I don't like to. Start bike. Voltage should vary with engine speed. Specs are in your shop manual, but 35V at a couple thousand RPM is probably about right.
If you passed that stator test and failed the first test, your regulator is shot. If you failed any part of the stator test, replace both regulator and stator.

 

Let me know if ya need a stator?
I got one, I'll let go pretty cheap.

 

Had a problem like you describe on my 1990 FXR-SP a few months after it was brand new. When replacing the rectifier I took the option of replacing the entire hot wire to the battery, good thing as I discovered the insulation worn through between the frame and the gas tank shorting to ground. I also rerouted the wire to below the engine.
After that no problems.

 

Charge battery on battery charger(not trickle charger) for one(1) hr. off the bike or at least disconnected from the bike.

Remove charger and immediately place a volt meter on the terminals, should read around 13.5 volts and a slow bleed down should begin. If it bleeds below 12.5 volts within a minute the battery is dead.

Purchase new battery. A battery has 6 plates in it. Each plate produces 2.25 volts for a total of 13.5 no load volts. If the battery doesn't reach this voltage on charge or decays to less then 12.5 volts in a minute or so it is dead.

 

Both my charging problems in the last 10 yrs. or so have been the voltage regulator. Replaced a battery once thinking it was that and it was the voltage regulator.

 

First thing I would do, is check the plug where the voltage regulator plugs into the stator. If it isn't positively connected, you will get what you got.

 

Check your stator for short to ground. I had the same problem with mine. The AC voltage output while running checked good as did the low ohms pin to pin. But when i checked each pin from stator to ground i had continuity from both pins so it was shorted to ground. Had to replace the stator and all is well now.

 

thanks for the replies. Dr. Hess' tests are spot on.

Went ahead and replaced regulator. That turn out to be a waste on money - although I now have a nice stator tester (cut off plug from old stator).

Checked resistance from each stator pin to ground and I have 100% continuity. There is also 100% continuity between two stator pins. Stator appears to be shot.

Very odd, as the stator is producing enough VACs (within specs) when tested.

Guess I'll miss my bike trip over labor day! :-(