Blowing fuse on start up

[Hoople]

looks like it was a loose earth all the time ...

It sounds good and we all want to believe it, but the reality of it is any loose connection adds resistance to the circuit which limits or reduces the flow of current on the fuse. That in turn helps the fuse not to blow.

If you did nothing else but tighten the connector, my guess is that in time that fuse will blow again.

 

[Mossberg]

Well, it was blowing every other time I started the bike, since tightening a week ago I've started it dozens of times with no problems at all.

Every time I start it I'm like "here we go" but nothing ...

*shrug*

 

[NEWHD74FAN]

Actually a bad ground can cause blown fuse if back feeding of active circuits takes place so that current flows where it is not supposed to go. I have had to troubleshoot circuits where the sneak currents were enough to force all the current to go thru one ground connection. I would check all the ground straps making sure they are good and tight. There are several near the front steerer and the one that ground the swing arm...couldn't hurt. :s

 

[Hoople]

Actually a bad ground can cause blown fuse if back feeding of active circuits takes place so that current flows where it is not supposed to go.

(?)
I think I understand what your saying but how does having ground loops increase the current flow throgh the positive leg of the circuit where the fuse is placed.

Yes, I could understand what your saying was true if the fuse was in the Ground side of each circuit. Then leak currents could transfer to a different fused circuit and blow an unrelated fuse. That I could understand.
But in this case the fuse is in the positive leg of the circuit. May be wrong but I can't see leak current caused by ground loops blowing a fuse in the positive leg of the circuit.

Just applying ohms law to a simple DC circuit and saying if I increase the resistance, the current is reduced. So if the current is reduced, it is less likely for the fuse to blow as long as the fuse is in the positive leg of the circuit..
But who knows.....anything is possible.

 

[Mossberg]

ok, it's not possible, because it did it again ...


A week of it being fine, then I go out today on a run and it blows. Then I meet some mates, stop to chat, try to restart the bike, and it blows.

Another fuse, we set off, 75 miles and 4 or 5 stop / starts later, no problem.

I've got home today, taken the seat and the covers off, and wiggled wires like a good 'un, but nope, that fuse will not blow now.

Most frustrating! I'm no genius with electrics either, which doesnt help.


It only does it in between alarm off / key in then before I hit the start button. Never when the bike is running.

Very annoying.

Oh, I've checked the charging, its doing about 14.2 volts, I expect thats ok?

The fuse that is blowing is called the battery fuse. Why is this? What does it protect?

 

[glider]

The 14.2 is a good reading for the charging system.

You may want to visualize the harness for any signs of chafing that would blow the fuse.

 

[Mossberg]

Yeah thats what I was doing earlier. Had the seat off, nothing obvious, had the r/h switchgear off, nothing obvious there.

Bloody irritating

 

[Hoople]

The fuse that is blowing is called the battery fuse. Why is this? What does it protect?

Your problem is not a straight forward issue and will probably require a schematic as I suggested back in entry point #6 of this thread. It would be nice if the answers to problems just fell from the sky but they don't.

You need to obtain a schematic for your electrical system.

 

[Mossberg]

With respect mate I'm not an electrical engineer, but I have been riding and messing about with bikes for 30-odd years.

A couple of pointers in the right direction and I can swap stuff about and disconnect stuff and see if I can find out whats wrong.

My question that you have quoted was why have Harley called that fuse a battery fuse in the first place.

If my fuel pump fuse was blowing I'd have an idea where to look ....

 

[Hoople]

A couple of pointers in the right direction and I can swap stuff about and disconnect stuff and see if I can find out whats wrong.

I can only speak for my 2009 but the Battery fuse is a fuse that is Hot all the time regardless of key position. Why the Moco named it the "battery" fuse I don't know because I can think of better names. Not ALL but most other fuses are switched ON by key position. What the battery fuse feeds would only be a guess for me because I don't have an exact schematic for your bike either. The problem you face is this. Besides knowing what the battery fuse feeds,, you also need to know the start relay circuit wiring, the bars start button control circuit wiring, the TSM/TSSM control circuit wiring, and unless another member comes along with a schematic, how will anyone (you & us) actually know what wires feed what with any confidence... Wire colors also can change color from year to year which adds to the frustration. If schematics were not available, I would understand. You may not have any choice. A company is NOT required by law to make service manuals available to the general public. But HD prints and sells schematics to ease the frustration while working on their products..

Sure, you can get lucky and come across the problem without spending the money ($15.00/ PDF version ) for a service manual. It does happen.
Best of Luck.