No electric power

merrow · March 16, 2013, 10:52:54 AM

1999 VF750-C

Was warming up the engine when I lost all electric power.

There is no power to the headlight, meters, etc. Battery reads 12.5V, jumping with a newly charged battery has no effect. I can jump the solenoid and spin the starter. The 10A and 15A fuses appear to be good. Jumping the negative post to the frame has no effect.

What am I missing?

TLRam1 · March 16, 2013, 01:39:43 PM

I think there may be a 30amp Main Fuse, i have never had to deal with that personally but others have. In lieu of that I would start from the battery with my meter check leads and see where I lose power.

merrow · March 16, 2013, 01:47:28 PM

Quote from: TLRam1 on March 16, 2013, 01:39:43 PM
I think there may be a 30amp Main Fuse, i have never had to deal with that personally but others have. In lieu of that I would start from the battery with my meter check leads and see where I lose power.

Thanks , Terry. I'm working on Merrow's bike for her; I lost downloaded shop manual in a computer crash and don't know the location of the main fuse.

Fiddle Mike

TLRam1 · March 16, 2013, 01:55:08 PM

Look under the Magna FAQ, there should be a link there for the Service Manual.

http://www.magnaownersoftexas.com/forums/index.php/topic,1917.0.html

merrow · March 16, 2013, 01:56:23 PM

Quote from: TLRam1 on March 16, 2013, 01:55:08 PM
Look under the Magna FAQ, there should be a link there for the Service Manual.

Again, thanks.

merrow · March 16, 2013, 02:49:49 PM

The 30A fuse is burned. Any guesses as to "why"?

TLRam1 · March 16, 2013, 02:53:56 PM

You have a wire rubbing against something and the insulation is worn off or pinched. Pull and look around the gas tank, headlight, steering neck, under the seat, rear fender, has anything been pulled lately and put back on....

You can use your meter and look for a dead short if you replace the fuse and it blows rapidly again.

TLRam1 · March 16, 2013, 02:57:16 PM

If you replace the fuse and it does not blow rapidly, start turning the steering wheel move wires around and see if you can replicate the condition that blew it in the first place.

lragan · March 17, 2013, 08:33:42 PM

Quote from: TLRam1 on March 16, 2013, 02:57:16 PM
If you replace the fuse and it does not blow rapidly, start turning the steering wheel move wires around and see if you can replicate the condition that blew it in the first place.

Gee, I hope this guy finds the electrical problem in time to come to MOOTMAG11! I have never seen a Magna with a steering wheel! Or any other motorcycle for that matter...

TLRam1 · March 17, 2013, 10:02:48 PM

Quote from: lragan on March 17, 2013, 08:33:42 PM

Gee, I hope this guy finds the electrical problem in time to come to MOOTMAG11! I have never seen a Magna with a steering wheel! Or any other motorcycle for that matter...

You haven't, you are missing something than.....

Smoked U · March 18, 2013, 06:55:17 PM

Quote from: lragan on March 17, 2013, 08:33:42 PM
Quote from: TLRam1 on March 16, 2013, 02:57:16 PM
If you replace the fuse and it does not blow rapidly, start turning the steering wheel move wires around and see if you can replicate the condition that blew it in the first place.

Gee, I hope this guy finds the electrical problem in time to come to MOOTMAG11! I have never seen a Magna with a steering wheel! Or any other motorcycle for that matter...

Picky, Picky, Picky

lragan · March 18, 2013, 10:38:56 PM

Picky Indeed! I especially enjoy tweaking Terry...

Smoked U · March 20, 2013, 02:51:43 PM

I haven't looked at a wiring diagram, but is it possible to blow the 30a fuse and not blow a sub system lower amp fuse? If so, doesn't this help track down the wiring path to the short/ground? I think this is right. Again, would this not indicate a heavy circuit like a starter or main battery power leads?

Magnum Magna · March 20, 2013, 11:03:47 PM

I had a friend that had a VFR that his Regulator was blowing his 30 amp.
I had two extra 30 amp it took both of them to make it home from work.

lragan · March 21, 2013, 01:40:44 PM

Quote from: Smoked U on March 20, 2013, 02:51:43 PM
I haven't looked at a wiring diagram, but is it possible to blow the 30a fuse and not blow a sub system lower amp fuse? If so, doesn't this help track down the wiring path to the short/ground? I think this is right. Again, would this not indicate a heavy circuit like a starter or main battery power leads?

Looking at wiring diagrams for the 3rd gen Magnas, you see that the charging system (alternator and Reg/Rect) charges the battery through the main fuse. If the regulator fails in full charge mode (certainly possible, as we have seen) either the fuse blows or the battery overcharges and, in the summer at least, overheats. Summer or winter this results in a ruined battery, if it goes on long enough. So the fuse protects the battery. I do not believe, based on my own experiments, that the charging system can crank out 30A at idle. So if the fuse lasts through starting, but not revving, the engine, then blows when you rev it up to 3000 rpm or more, look to the Reg/Rect as the culprit.

If the fuse blows at random intervals unrelated to engine speed, check out the wiring from the main fuse (at the starter solenoid) to the ignition switch and from the ignition switch back to the fuse block. You might also examine the ignition switch, but I think it is unlikely to be the culprit.

Dave is generally correct that other circuit faults should result in the lower amperage fuses going first, or at the same time, as the 30A main fuse. Fuses, however, are notoriously inaccurate, and blow at different speeds with different overloads. If any of the fuses in the fuse block happen to be slow blow type, replace them with regular fuses and try it again. If one of them blows, then you know where to look.

These kinds of intermittent problems can be exasperating. Hang in there. With a cheap voltmeter and a lot of patience, you can eventually sort it out.