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Voltage Regulator HELP

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Old 10-15-2011, 10:59 AM
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Question Voltage Regulator HELP

Voltage Regulator: 2009 FLHTCU 33k miles.... New Battery , Load Test is OK

So what are the signs the Voltage Regulator is going bad ?

Or do you have to wait till it just stops working ?

Symtoms: Start up Volts sit at 10.5 - 12.5 issh - start to ride goes to 14.3

Come to stop light: drops to 13.0 isssh then moves up to 14.0 then sometime drops to 12.0
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Old 10-15-2011, 11:04 AM
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Don't trust the gauge alone, take true voltage readings.
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Old 10-15-2011, 11:16 AM
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At idle mine's under 12 Volts. The only thing I watch for is a consistent 13.5 volts at 2000 rpm and above. No wavering needle, no varying voltage, just 13.5 Volts

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Old 10-15-2011, 11:17 AM
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I had an intermittent low voltage problem - the volt meter would drop below 12vdc, and the CEL would come on and throw a P0562 DTC (no other codes present)... it would stay in the low voltage condition and come out after @ 1 minute... this would happen regularly...

turned out to be the voltage regulator. Good luck with your troubleshooting.

2008 FLHTP - 103 ci, 6-Speed, ABS, Fullsac true dual kit, Rush 2.0 Slip-ons
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Old 10-15-2011, 12:52 PM
cooper57M cooper57M is offline
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At idle my bike always read 14 volts. Never goes under that
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Old 10-15-2011, 12:59 PM
mkguitar mkguitar is offline
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those readings as described seem normal.

bad regulator may display any or all of these:

allow voltage above 14.8 VDC to reach the battery ( damaging the battery)

allow AC volts to pass through

allow power from the battery to drain when bike is not running


the alternator produces about 16 to 20 volts AC per 1000 rpms.

the regulator converts that voltage ( could be over 100 volts AC) to DC and "regulates" to less than about 14.8 volts DC.

the voltmeter in the dash, is not tremendously accurate, but can give an indication of function-- if you see it reading way high or way low, then further investigation is needed.

but readings taken with a real voltmeter at the battery and alternator plug are needed for real charging system diagnosis-- again, if a problem exists.

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Last edited by mkguitar; 10-15-2011 at 04:02 PM.
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Old 10-15-2011, 02:49 PM
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If the bike is not throwing any historic low voltage DTC's (CEL and Low Volt Light coming on), I wouldn't work about what the gauge says... keep on riding.

2008 FLHTP - 103 ci, 6-Speed, ABS, Fullsac true dual kit, Rush 2.0 Slip-ons
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Old 10-16-2011, 11:24 AM
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I am having the same code and problem with charging and not charging, will have to look into the regulator.
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