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K100-forum.com » Technical, repair and troubleshooting » Electrical » Temperature sensitive charging system on 1985 K100

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flyinglow

flyinglow
Silver member
Silver member
I have a 1985 K100 RT with 35,000 miles that I purchased a year ago.  I have added voltage and coolant temperature meters to the fairing so I can monitor these items while riding.  My voltmeter reads a good 13.5 to 14 volts when driving.  But, as the engine gets warmed up, especially on hot days,  the voltage slowly goes down to about 12. 5 to 13 volts.   I have a new battery and cleaned all the ground connections.  The brushes look good so my guess is to replace the regulator with a new one.
Temperature sensitive charging system on 1985 K100 20171010
Temperature sensitive charging system on 1985 K100 20180611

    

duck

duck
Life time member
Life time member
It might not be the voltage but the gauge being impacted by heat. Try running a digital voltmeter in tandem with the gauge to see what that shows before spending money on parts.

(PS: Your dash pad with ignition and other switches is upside down.)


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Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
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Dai

Dai
Life time member
Life time member
It quite probably is the regulator. That alternator has suffered a severe short at some time in its history (the red cable shows overheating). I'd replace all of the battery cables, including the earth lead.


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1983 K100 upgraded to K100RS spec, 1987 K100RT
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4Back to top Go down   Temperature sensitive charging system on 1985 K100 Empty Dead Short Thu Feb 14, 2019 3:57 am

flyinglow

flyinglow
Silver member
Silver member
Yes, I saw the melted wires and did replace all the power and ground wires.  Thanks.

    

5Back to top Go down   Temperature sensitive charging system on 1985 K100 Empty Bad Voltage Regulator Thu Apr 04, 2019 5:43 am

flyinglow

flyinglow
Silver member
Silver member
Its still cold in Minnesota but I did just replace the regulator / brush assembly with a new one.   One of the brushes was worn more than I thought and the other looked good so it could of been bad brushes.   It appears to work fine now but I won't really know until the weather gets really warm.  Thanks for everyone's input.

    

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