Testing a Harley Charging System

Jack Klarich · Oct 19, 2016

Step by Step Instructions for Testing Your Harley’s Charging System

Battery Test: The battery needs to be a fully charged battery that has been load tested to ensure proper readings. If you are not working with a fully charged and functional battery, all other voltage tests will be incorrect. Most places like Auto Zone, Advance Auto, and Pep Boys will charge and test motorcycle batteries for free. Standing battery Voltage should be 12.5-13.2 DCV.
Charging System Voltage Test: Start motorcycle, Measure DC Volts across the battery terminals (you should have a reading of approximately 13.2-15 DC Volts).
Check Connections/Wires: Inspect the regulator/stator plug, and check the battery terminals for connection/corrosion. If everything seems to be in order, move on to number 4 below to determine if there’s a failed component.
Stator Checks/Rotor Check: Each of the following tests isolate the stator & Rotor, If AC Output test Fails and Resistance Check, and Stator IB Test Pass then Rotor is at fault (Pull Primary covers and inspect rotor for damage).
- AC Output Check:
  1. Unplug the regulator plug from the stator
  2. Start motorcycle and change Voltmeter to AC volts.
  3. Probe both stator wires with your meter leads.
  4. The motorcycle should be putting out approximately 18-20 ACV per 1,000 rpm.
    
    (Reading will vary depending on system, check service manual specification)
  5. Generic Specs:
    - 22 amp system produces about 19-26 VAC per 1,000 rpm
    - 32 amp system produces about 16-20 VAC per 1,000 rpm
    - 45 amp system produces about 19-26 VAC per 1,000 rpm
- Stator Resistance Check:
  1. Switch your multi meter to Ohm x 1 scale.
  2. Probe each stator wires with meter leads and check resistance on meter.
  3. Resistance should be in the range of 0.1-0.5 Ohms. (Reading will vary depending on system, check service manual for specification)
  4. Generic Specs:
    - 22 amp system produces about 0.2 to 0.4 ohms
    - 32 amp system produces about 0.1 to 0.2 ohms
    - 45 amp system produces about 0.1 to 0.2 ohms
- Stator IB test or Ground Check:
  1. Switch your multi meter to Ohm x 1 scale.
  2. Probe each stator wire with your positive lead on multi meter and the negative to ground.
  3. There should be no continuity to ground on either wire.
  4. If there is continuity to ground your stator is shorted to ground.
Regulator Test: Each of the following tests isolates the regulator only, so if any of these tests fail, the regulator is at fault.
- Identifying Wires:
  1. Battery Charge Lead– Wire going from regulator to battery positive.
  2. AC output leads– Wires coming from the Stator to regulator.
  3. Ground– Wire from Regulator to ground or regulator may be grounded via the physical bolting to chassis.
- Regulator Ground Test: Insure the regulator body is grounded or grounding wire is fastened tight to a good ground (you should verify this by checking continuity from regulator body to chassis ground).
- Fwd/Reverse Bias Test/Diode Test: This check is testing the Diode function to ensure it is regulating the AC current for the stator into DC Current.
  1. Switch multi meter to Diode Scale.
  2. Place your Multi meter positive lead on each AC output wire.
  3. Place your multi meter negative lead on the battery Charge wire.
  4. The meter should read voltage typically around .5 volts.
  5. Next, switch your multi meter leads putting the negative lead on the AC output wires and the Positive lead on the Battery Charge Wire.
  6. The reading should be Infinite.
  7. With your meter on the same setting, place your multi meter positive lead on the regulator ground wire or to the regulator directly, and then place your meter negative lead on the AC output leads.
  8. The meter should read voltage typically around .5 volts.
  9. Next, switch your multi meter leads putting the negative lead on the regulator ground and the Positive lead on the AC output wires.
  10. The reading should be Infinite.
  11. Note: Below is a table to show the readings:

Positive Lead	Negative Lead	Reading
AC output 1	Battery charge lead	Voltage
AC output 2	Battery Charge Lead	Voltage
Battery charge lead	AC output 1	∞
Battery charge lead	AC output 2	∞
Ground	AC output 1	Voltage
Ground	AC output 2	Voltage
AC output 1	Ground	∞
AC output 2	Ground	∞

Replacement Components

Batteries:

350-430 (97-09 FLT, FLH, FLHT Dressers)
350-431 (82-94 FXR, 84-90 Softail, 71-86 FX, 79-96 XL)
350-432 (91-09 Softail, 97-09 Dyna, 97-03 XL)
350-433 (80-96 FLT, FLHT, 93-96 FLHR)

Stators:

380-864 (L84-90 XL)
240-556 (91-06 XL)
381-259 (70-75 Big Twin 15 Amp)
381-084 (76-80 Big Twin17.8 Amp)
381-260 (81-88 Big Twin 22Amp)
381-202 (89-99 Big Twin 32 Amp)
381-596 (00 Softail, 99-03 Dyna)
381-594 (99-01 Touring)
381-595 (02-05 Touring)

Regulators: (Offered in Chrome and Black, Black Part numbers listed below)

380-798 (84-85 XL)
381-177 (86-90 XL)
381-014 (91 XL)
380-797 (92-93 XL)
380-485 (94-03 XL)
381-835 (04-06 XL)
383-089 (07 XL)
381-252 (70-75 Big Twin)
381-328 (76-80 Big Twin)
381-327 (81-88 Big Twin)
381-277 (89-99 Big Twin)
381-605 (00 Softail)
381-603 (97-01 Touring)
381-606 (00-03 Dyna)

Rotors:

380-373 (70-06 Big Twin 18, 22, 32 Amp Systems)
380-374 (95-06 Big Twin 38 Amp Systems)
380-375 (97-05 Big Twin 45/48 Amp Systems)
383-640 (84-90 XL)
383-641 (91-03 XL)
383-642 (04-09 XL)

Remember to fully charge your battery first or your tests results will not be valid.

desertclassic · Oct 19, 2016

Electrical stuff has always kicked me in the butt. House stuff has never been a problem, I sure understand that, but autos and bikes drive me crazy. I have a best bud that is a super elec guy. He makes a living out of it. I give him a call and he takes care of me and I always do the mechanical stuff for him. Jim

Phu Cat · Oct 26, 2016

Thanks Jack, I'll put that in my folder of tech tips I've picked up from others. It's well appreciated.

There is one really quick check for a stator that I can't remember if I posted here before: (please excuse me if I did).

If you're having trouble with you're charging system, just take off the clutch cover and smell the atmosphere. If it smells like burnt varnish (rather than just oil) your stator is definately shot.

PC

Keystone · Oct 27, 2016

Great post! Keep it at the top for awhile!

Jack Klarich · May 3, 2017

I will and thank y'all 4 having me :clapping:

grandpawj · Jun 26, 2017

Jack, thank you for all you do!! I just went to the HDTalking forum, of which I am also a member, and downloaded the '08 Electrical Diagnostic Manual you posted in one of your threads. I have also copied and printed your post in this forum for HD DTC's. You get a gold star!

Jack Klarich · Jun 26, 2017

This is an example of my work @ that other forum I helped rebuild the self help section. A lot of the info there was hand picked by me and has been tried and trued by me over many years. Others have tried to copy me and become me. I am self banned there now, Not a big deal any more. I fit in here, Not so much there any more, TOO much trouble with the Moderators and some nameless members there. Now back to this Forum, Thank y'all

for havin me