Testing regulator, need help
Testing regulator, need help
I had the eng light and battery light come on on my 2008 Ultra. Bike off I get 13.6 volts. Same at idle.
Stator continuity test was good. I unplugged the stator and had about 20 volts at each wire at idle.
I then check the stator side of the regulator and had about 12.6 volts at each of the posts.
Next I tried the diode test on the regulator. The only time I got a reading was with the neg lead from the meter to the pos socket of the charge side of the regulator, positive lead to each of the stator posts. 360 at all 3 stator posts. No readings at all with the other 3 combinations.
Does this sound like a bad regulator? Would I be safe trying a new regulator or would a bad stator burn it up?
Stator continuity test was good. I unplugged the stator and had about 20 volts at each wire at idle.
I then check the stator side of the regulator and had about 12.6 volts at each of the posts.
Next I tried the diode test on the regulator. The only time I got a reading was with the neg lead from the meter to the pos socket of the charge side of the regulator, positive lead to each of the stator posts. 360 at all 3 stator posts. No readings at all with the other 3 combinations.
Does this sound like a bad regulator? Would I be safe trying a new regulator or would a bad stator burn it up?
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
when you attach a meter at the battery with the motor running ( and you can rev it up)
you should not see any DC voltage above 14.8 volts DC
( and the AC volts at the stator should be 16~20 per 1000 rpms- this may vary I don;t have a manual for your bike)
you should not see an AC volts at all ( at the battery- the diode bridge recitifier will take off the tops and bottoms of the AC sine wave = DC voltage
another result of bad diode is voltage draining back thru the VR to ground from the battery when the bike is off- an ammeter will show any current flow back wards.
the tech board electrical section has a sticky with full diagnostics- read through that
Mike
you should not see any DC voltage above 14.8 volts DC
( and the AC volts at the stator should be 16~20 per 1000 rpms- this may vary I don;t have a manual for your bike)
you should not see an AC volts at all ( at the battery- the diode bridge recitifier will take off the tops and bottoms of the AC sine wave = DC voltage
another result of bad diode is voltage draining back thru the VR to ground from the battery when the bike is off- an ammeter will show any current flow back wards.
the tech board electrical section has a sticky with full diagnostics- read through that
Mike
Seasoned HDF Member
Joined: May 2012
Posts: 32,934
Likes: 36,027
From: Carlsbad, CA
There are stickys in the electrical section on how to check the charging system. But in my opinion, 85% of the time the engine and battery light comes on, it's the regulator.
Btw...your open load stator test at idle sounds right. You might want to rev the motor and ensure the voltage increases. But, if it reads about 20 VAC at idle across all the leads...it's probably Ok.
Some of your other readings are confusing.
Soooo...save some time, and just buy a regulator. Also, while you are in there, if your battery is more than 5 years old I would replace it for good measure. Plus, if the regulator hasn't been charging it fully for a while...it's days are numbered.
Good luck..
Btw...your open load stator test at idle sounds right. You might want to rev the motor and ensure the voltage increases. But, if it reads about 20 VAC at idle across all the leads...it's probably Ok.
Some of your other readings are confusing.
Soooo...save some time, and just buy a regulator. Also, while you are in there, if your battery is more than 5 years old I would replace it for good measure. Plus, if the regulator hasn't been charging it fully for a while...it's days are numbered.
Good luck..
The battery is less than a year old, always kept on tender.
Would a bad stator destroy the new regulator?
I read the sticky in the Electrical Tech section. Sounds like tests described are for an earlier model.
"Step 2. To check the regulator unplug it from the stator. Take a test light and clip it to the negative terminal of the battery and then touch first one pin and then the other on the plug that goes to the regulator. If you get even the slightest amount of light from the test light the regulator is toast.
To do this with a meter: black lead to battery ground, red lead to each pin on the plug, start with the voltage scale higher than 12vdc and move voltage scale down in steps for each pin. Any voltage is a bad regulator."
Does the above step describe NOT having any DC voltage on the stator side of the regulator? I have 12.6 V at each of the 3 posts
Would a bad stator destroy the new regulator?
I read the sticky in the Electrical Tech section. Sounds like tests described are for an earlier model.
"Step 2. To check the regulator unplug it from the stator. Take a test light and clip it to the negative terminal of the battery and then touch first one pin and then the other on the plug that goes to the regulator. If you get even the slightest amount of light from the test light the regulator is toast.
To do this with a meter: black lead to battery ground, red lead to each pin on the plug, start with the voltage scale higher than 12vdc and move voltage scale down in steps for each pin. Any voltage is a bad regulator."
Does the above step describe NOT having any DC voltage on the stator side of the regulator? I have 12.6 V at each of the 3 posts
Seasoned HDF Member
Joined: Jun 2006
Posts: 30,860
Likes: 32,730
From: King George, VA
The battery is less than a year old, always kept on tender.
Would a bad stator destroy the new regulator?
I read the sticky in the Electrical Tech section. Sounds like tests described are for an earlier model.
"Step 2. To check the regulator unplug it from the stator. Take a test light and clip it to the negative terminal of the battery and then touch first one pin and then the other on the plug that goes to the regulator. If you get even the slightest amount of light from the test light the regulator is toast.
To do this with a meter: black lead to battery ground, red lead to each pin on the plug, start with the voltage scale higher than 12vdc and move voltage scale down in steps for each pin. Any voltage is a bad regulator."
Does the above step describe NOT having any DC voltage on the stator side of the regulator? I have 12.6 V at each of the 3 posts
Would a bad stator destroy the new regulator?
I read the sticky in the Electrical Tech section. Sounds like tests described are for an earlier model.
"Step 2. To check the regulator unplug it from the stator. Take a test light and clip it to the negative terminal of the battery and then touch first one pin and then the other on the plug that goes to the regulator. If you get even the slightest amount of light from the test light the regulator is toast.
To do this with a meter: black lead to battery ground, red lead to each pin on the plug, start with the voltage scale higher than 12vdc and move voltage scale down in steps for each pin. Any voltage is a bad regulator."
Does the above step describe NOT having any DC voltage on the stator side of the regulator? I have 12.6 V at each of the 3 posts
Seasoned HDF Member
Joined: Jun 2006
Posts: 30,860
Likes: 32,730
From: King George, VA
You might consider using dielectric grease on the connector when installing your new reg. You can buy that in little packets at most automotive stores. Usually by the checkout counter.
Trending Topics
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
The Best and Worst Harley-Davidson Moves of 2025
Verdad Gallardo
I have been doing a lot of reading on the regulator and it looks like it is definitely bad.
Diode test showed current/flow? in only one of four combinations....should be two of four.
Also, with the charging side of the regulator plugged in I am getting a voltage reading on the stator side.
I'm sure my stator is weak but I'm hoping this will get me on the road for a bit while the weather is nice. Once days get shorter I plan to replace the stator and compensator.