Intermittent Alternator ?


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Aug 19, 2008
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Everywhere I dont really want to be...

Weird this. Ive just returned from a 3000km trip around France - Switzerland to Spain and back.

The bike '03 1150GSA (New engine last year 17K mile donor bike - fine around Scotland last year) was fine for the first and second day. At the end of the first day (250Miles) I noticed the RED Triangle "ON". In the morning of the second day, the triangle was still active. I checked the lights and all seemed OK. I figured "gremlin" Old bike...
At the end on the second day and another 250 miles (more or less). I stopped the bike to "Check the flora" and the battery was flat...just "Click" trying to restart..No alternator light came on (It does work! Checked active on power on). Bump started and bought a charger the following day. It took a full 12 hours to charge. We checked all connections, battery, starter etc. A local garagiste said the alternator was providing minimal volts but wasn't providing a full output. Even raving the bike didn't change the voltage > 13.1V or so

I got home by disconnecting all the running lights and not using brakes or indicators (middle of three riders) and recharging every night camping.

Strangely after that the Battery required a minimal charge (10 minutes or so at 2AH)

Ive checked this evening and the battery at rest is 12.4 V and at idle its 13.8 V. Seems OK.Haven't checked he running speed yet ( one pair of hands, no clips). But everything seems OK. Just dont want to get stuck somewhere.

I cant find an alternator easily on-line - Its "regulators and belts" which leads me to believe that these items dont fail, but the change of the belt and regulator is a more serviceable thing....

Should I just change the regulator and belt for peace of mind or keep looking for a fault ?:nenau

Opinions ?
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Alternator change on the 1150 is a simple operation and being a proper car type unit any auto electrician or rebuilder can bench test it and rebuild if required .

I would check the connectors at the rear of the alternator first
If the alternator lamp did not come on? it's not getting current to excite the stator and generate electricity

Remove blue wire from rear of alternator and ground it out with the ignition on

You should get the Battery lamp illuminated? If not, check and replace the bulb and try again

Once you have that working reconnect to the alternator and check that it illuminates when the ignition is on

Alternator should function correctly after that

If the battery lamp does illuminate when you ground it? It could be sticking brushes or a duff rotor and any half decent auto or commercial starter / alternator repair service should be able to test / repair it for you
Check the thin blue wire that's attached to the alternator isn't corroded or frayed
Check the thin blue wire that's attached to the alternator isn't corroded or frayed

Good point if it isn't making a good connection or even worse connected to the terminal it cannot do any exciting of rotor coils to generate electricity

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