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Charging system I have a 1993 fatboy flstf. I have replaced the battery, the voltage regulator, and still cannot keep a charge on the battery. Could it be the stator, and if so can a novice tackle that? Or is there something else I can check first? I don't have the money to take it to a shop right now, but I'm willing to buy the parts if I can take care of it myself. Thanks in advance. Kevin

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Could be a bad ground, but u have some work to do if you dont find it. Try charging up yer battery ....put a multimeter on it and check the reading... Then fire it up and check the reading......voltage should increase while its running ( to about 13.5-14 volts)....if it decreases - u have a charging problem, and if u replaced the could be the stator ... Take off the inspection cover on the primary - Is there a burnt smell ?

Problem is....replacing the stator isnt a simple have to remove the compensating sproket and clutch....I wouldnt mess with it unless u know what your doing

Posted on Aug 19, 2008

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Sounds like a bad ground you should check all of your ground wires ...there can't be that many of them if not that do you have a alternator if you do take the positive wire off while it running if it dies that would be your problem...good luck

Posted on Aug 15, 2008


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Looking for help charging system not charging battery on 1999 Harley Davidson fatboy

Check regulator ground by using an ohmmeter with one lead on a known good ground, such as the battery ground cable, and the other on the regulator base.
The connection where the alternator stator wires plug into the regulator could be corroded/dirty and need to be cleaned and sprayed with electrical contact cleaner and protected with dielectric grease because corroded wires going to the battery or alternator from the stator or the regulator will affect the ability of the charging system to properly charge a battery.

Motorcycle voltage regulator connections must be clean and tight for proper operation so it must be verified that both the AC (stator) connections and the DC (battery supply side) connectors are clean, fully inserted and locked in place with the regulator latches (they should also be coated with dielectric grease to keep them clean and corrosion free).

The motorcycle voltage regulator is a series regulator that is also a rectifier that changes stator supplied alternating current (AC) to direct current (DC) which the battery system requires. If the charging system does not keep the battery properly charged both with regards to Voltage (between 13 VDC minimum and 15.5 VDC maximum) and the current supply at a high enough amperage to meet the system lighting, ignition, TSM/TSSM, security and accessory requirements plus a minimum of 3.5 more amps (3.5 amps more than the foregoing system requirements) there are a number of tests that can be done to ascertain why.

As the voltage regulator must have a good, clean, tight (and otherwise secure) ground connection for proper operation a Voltage Regulator Ground Circuit Test can be accomplished by connecting an ohmmeter to a known good ground (like the battery negative post) and the case of the regulator. If there is continuity with little resistance the ground is GOOD and nothing more needs to be done BUT if there is NO continuity or there is more than minimal resistance the ground will need to be fixed so there is a low resistance continuity by either locating and fixing the poor ground or adding a new grounding wire from the regulator case to a know good ground.

A Voltage Regulator Power Circuit Test can be accomplished by turning OFF the Ignition, disconnecting the voltage regulator and with an ohmmeter set to the Rx1 setting, testing for continuity between the voltage regulator wire harness supply terminal and the main fuse terminal (with the fuse removed) and if there is continuity present then the wiring circuit here is GOOD but if there is NO continuity then you will need to either find the open and repair it or replace the whole wire running from the voltage regulator to the main fuse.

As there should be no short circuit in the power supply from the regulator to battery (main fuse) wiring OR in the regulator internal circuitry continuity from these both need to be checked again with an ohmmeter set to the Rx1 setting. If the regulator to main fuse wiring connector is not disconnected from the regulator you can connect an ohmmeter with one lead on the regulator supply wire terminal end at the main fuse (with the main fuse removed) and the other lead to a known good ground. If there is NO continuity then you know that both the supply wire and the regulator are okay (as there is no short to ground). BUT if there is continuity then either the regulator or wiring or both is/are shorted to ground. To determine where there is a short circuit (i.e. either the wiring or the regulator internal circuitry) you must disconnect the DC side of the wiring harness (the connector at the DC side of the regulator) from the regulator and test between either or both ends of the wire i.e. from the regulator wire harness.

AC Output Check
Disconnect the voltage regulator connector from the alternator stator wiring and then connect an AC voltmeter across both stator sockets of a two wire stator, or if a three wire stator across two of the three for example 1 & 3 and then later you will repeat the test between 2 & 3 and later between 1 & 2. THEN run the engine at as close as possible in the circumstances to 2000 RPM. The AC output should be approximately 32-40 VAC, approximately 16-20VAC per 1000 RPM. If you have done a stator static test and the stator has proven to be in good mechanical condition and the AC output is below specifications, the charging problem is going to be a faulty rotor. If you have not done a static stator check yet and the AC output is less than as set out above it may be that the stator is defective and the static stator check will need to be done. While the regulator has nothing whatsoever to do with the alternator output, if the alternator output is good the regulator might be defective in either rectification or in limiting the output to the battery to under 15 VDC. If AC output is low and the stator has passed the static stator check then it is likely that the permanent magnets in the alternator rotor are weak. A permanent magnet can lose its magnetic strength if it is dropped or shocked such as letting it snap into place when being installed or possibly by use of an impact wrench to remove the compensator fastener etc.

May 27, 2014 | Harley Davidson FLSTF - FLSTFI Fat Boy...

1 Answer

1993 Jeep Wrangler charging problem

nothing wrong with the ECM unless it has the voltage regulator as part of the system
indicates faulty wiring and faulty alternator
have a load test done on the battery
have an auto electrician do a full charging system check
charging voltage should be 14.5-14.8 volts DC
battery voltage should be 12-13.5 volts dropping to 11 volts when cranking the engine
make sure that the drive belt tension is correct and the belt is in good condition

Dec 22, 2017 | 1993 Jeep Wrangler

1 Answer


Hi Anonymous, main circuit breakers are underneath the instrument panel or seat. But more than likely it's your alternator or voltage regulator. Ther are a few things you can do to isolate the problem. Start with a charged battery 12.5 volts or better and cables are clean and tight as with all your electrical connections. Disconnect your alternator plug and with a muliti meter set it to the lowest ohms scale, one lead to ground the other to any alternator wire the meter should read zero, do the same with the other wire. Next touch both wires with meter leads you should get 0.1 to 0.2 ohms. Also put one lead to ground and one lead to voltage regulator mounting bolt or stud the meter should read zero. Then switch your meter to the AC volts scale fire up the bike and the meter should read 16 to 20 volts AC for every 1,000 RPM the tach reads, if you have no tach it should read 16 to 20 at an idle. If all the numbers check out ok then you have a good stator and probablly rotor. Remove your voltage regulator and check for swelling, cracks or burnt smell/look. If your going to throw parts at it start with the voltage regulator. A normal charging system will read 14.3 to 14.7 volts DC at the battery with the engine at 3,000 RPM. Good luck

Apr 14, 2014 | 1993 Harley Davidson FLSTF Fat boy

1 Answer

Voltage regulator rectifier

Hi Mike, perform the following tests:
1. Fill acid type batteries to proper levels.
2. Charge battery overnight at 1-2 amps you need 12 volts or better after charging.
3. Make sure all connections are clean and tight especially the negative cable at both ends.
4. Hook up volt meter to battery and start engine, if meter falls below 9.5 v replace battery.
5. With engine running at 3600 RPM battery should read 14.3-14.7 volts if not continue tests.
6. Unplug voltage regulator from alternator at crankcase by front of primary cover.
7. To test voltage regulator go to:
8. With ohm meter, one lead grounded, touch alternator pin meter should read infinity, if not replace stator.
9. With ohm meter, both leads touching alternator pins meter should read 0.1 to 0.2 ohms on 1989 and later models. 0.2 to 0.4 ohms 1988 and earlier models, if not replace stator.
10. With volt meter set on AC scale, both leads touching alternator pins meter should read
16 to 20 volts AC for every 1000 RPM'S 1989 and later and 19 to 26 volts AC for every 1000 RPMS. If not replace rotor. Good luck

Jun 13, 2013 | 2011 Harley Davidson FLSTF Fat Boy

1 Answer

Power poblem

check to see if its charging as you ride,, Keep in mind that Harleys hate start and stops,, once you start them they draw alot of power from the battery,, and should be ridden for a long time to recharge the battery ,, with the post connections hooked up, use a volt meter to check the charging,, it should read between 13-15 volts ,, if not you have a regulator problem

Aug 02, 2010 | 2001 Harley Davidson FLSTF - FLSTFI Fat...

2 Answers

I have a 1993 cbr900 i bought a brand new battery and 2 days l8tr it was dead what will cause my batteries to keep getting drained while riding my bike??

The first place I would look is the voltage regulator. When they start to go out, they will continue to drain amps from the battery even when the bike is off. An ohm meter can test to see if there is continuity there when the bike is off. If so, replace the regulator. Pretty easy to test/diagnose the regulator.

Jun 11, 2010 | Motorcycles

2 Answers

I have a 2000 fatboy stopped to get gas battery was dead charge battery went bought new battery after 1 hr of riding battery was dead again is this a voltage regulator or a stator problem how do I check

To check if you got a charging fault, get a multimeter and switch to voltage put across the battery. You should be getting at least 13.4 volts.
Turn lights on and this should fluctuate upwards. If your getting anything lower then what I stated you have a charging problem. Rectifiers and regulators can only really be tested of the bike with a specific tester. Hope this helps, let me know how you get on.


Apr 05, 2010 | 2000 Harley Davidson FLSTF Fat boy

1 Answer


Tour problem is in the voltage regulator inside the alt.
Replace the alt.

Oct 24, 2008 | 1993 Jeep Grand Cherokee

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