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Discussion Starter · #1 ·
Loaded the wife on the bike and dog in his trailer and fired up the bike yesterday. Noticed right off there was a whining noise coming through the headset. Checked the voltage and saw it was sitting at just over 12 v. Figured I lost the alternator again. It's a Compufire. I lost it earlier after only 7,000 miles and had it rebuilt. Have put 11,000 miles on it since the rebuild. At the same time I had the Compufire rebuilt I had the OE alternator double checked( showed good) so kept it for an emergency spare. Thinking this is just such an emergency, I pulled the Compufire and put the OE back in. Fired it up and same thing, voltage at battery level and noise in the headset. I had rode the bike in some light rain returning from a campout a few days earlier and charging system was okay. All electrical systems are working just fine other than the charging. I did have to weld on the rear end 2 weeks ago. It has a Moto Trike kit on it and the top left swing arm mount broke off the rear end. Design flaw from MotoTrike - not enough bracing on this mount in my opinion. Anyway, when I repaired the mount I disconnected the battery and took out the main fuse links plus grounded right at my work. The bike performed well for several days and now this. Anyone have an idea as to what would cause the charging system to go out just sitting in the garage? By the way I always keep the bike on a battery maintainer when not being ridden.I am at a loss as to what would cause this. I pulled the trailer connection apart to see if there might have been a direct short in there from the rain but it's okay. Will ask the Sgt. Major ( wife) to take them both in tomorrow to be checked out and rebuilt if nec. Anyone have any ideas as to what else I should be looking at or for?
 

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Check the voltage at the alternator, both the output and the exciter terminal.
 

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Thanks Dave, Will test it before I yard the current alternator out.
If you checked the voltage and got only 12 volts, this I assume you have all the electronics turned on, did you see any voltage drop below 12 volts. If your answer is yes, then most likely it's the alternator, if the answer is no, then you have a huge current draw somewhere which is loading the alternator beyond capacity. This would also explain the increase in the whine you are hearing.
If I recall correctly, the Compufire doesn't have an external capacitor however the fuel pump does have one, remove the ground side of this capacitor and see if the voltage increases, the whine will still be there but if the capacitor is leaking your voltage may increase. Also the Compufire internal filter may be shorted.
 

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That's certainly a weird one. I can't believe both good alternators went south at the same time doing the same thing. I tend to agree with Terry and Dave. The thing is it would have to be one heck of a draw to pull it back to battery voltage. Wait, on second thought maybe not. Did you try revving the engine some and check voltage? Might be at idle the output is not real high and even a relatively small (or medium) draw might cause the voltage drop. I would say that IF voltage rises significantly with acceleration it probably is parasitic load somewhere. Now to find it. Maybe start pulling fuses little by little. The ones you can anyway.
 

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What are you checking the bike voltage with, i.e. are you using the voltmeter on the bike or a multi-function unit.
 

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Discussion Starter · #7 ·
Problem solved! With Dave and Terry's help I was able to locate the problem. Terry, thanks for the phone call and teaching me more about troubleshooting electrical components than I will be able to retain. Anyway, after pulling all the fuses one at a time while idling nothing changed. Double checked the alternator with a meter and low and behold if there wasn't 13.78 volts at 850 rpm. I then checked the power at the voltmeter and was only getting 12.2 v. I then checked where the alternator feed goes into the main fuse block. 13.77 V. At the top of the fuse block only battery voltage. Grabbed the trusty # 2 Phillips and was able to get not quite a 1/4 turn on the bottom screw for the fuse link. Yep, you guessed it 13.77 volts going into the battery. Think my initials should be DW for Dip Wad. Too many hours at work and taking things for granted in being sure it was the alternator again made for a terrible judgement call . Lesson learned and again thank everyone for their help. This just proves what a great site this is and what the caliber of the folks are that help out.
Again many thanks!
 

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Terry helped me with a headset problem recently...he's a great guy and a valuable resource!
 
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