Author Topic: Main fuse melting (Read 5077 times)

singedebile · « **on:** October 24, 2011, 11:25:26 AM »

-Main fuses have been blowing now and then for some time
-Cleaned the contacts on the fuse block... same problem
-Re-soldered the connections on the fuse block.... same problem

Finely culminated to the point where on a trip with some friends the fuse block melted so badly that the connection severed completely.. i barely rigged something to limp home

I know my wiring harness has some issues that I need to resolve, in particular the ground.. is it possible that a bad ground with too much resistance would transmit that to the fuse block?

('75 cb550F)

Rigid · « **Reply #1 on:** October 24, 2011, 11:26:59 AM »

What size fuse are you using?

singedebile · « **Reply #2 on:** October 24, 2011, 11:51:55 AM »

15A

the fuse has been getting hot when I ride the bike,
and its worth mentioning my fuse block is pretty melted now around the top of the main fuse... I am planning on rewiring the whole harness this winter, but I'd like to get some ridding in before then.

..

crazypj · « **Reply #3 on:** October 24, 2011, 12:02:46 PM »

Do you have stock headlight or have you 'uprated' with a 60/55 H4 bulb?

Rigid · « **Reply #4 on:** October 24, 2011, 12:03:54 PM »

You can solder in a new blade type automotive fuse in place of the oem set-up. It might save you some pushing.

singedebile · « **Reply #5 on:** October 24, 2011, 12:26:00 PM »

yeah the bike is pretty much stock,

When i redo the wiring harness I was planning on putting in a new fuse block. I really thought though having proper re soldered the connection would have fixed any problem the block itself could have been making.

so is that a no about the resistance of a bad ground creating the heat to melt the fuse & fuse/block?

singedebile · « **Reply #6 on:** October 24, 2011, 07:45:55 PM »

nobody?

, i guess i'll just keep poking at it

fmctm1sw · « **Reply #7 on:** October 24, 2011, 08:19:46 PM »

What does the fuseholder look like? Look at a before and after of mine. Never blew again. 3000 or so miles...

phil71 · « **Reply #8 on:** October 24, 2011, 09:16:07 PM »

you've got a big draw there. Really, the only thing that can draw that kind of current is the stator. The stator can only do that if the rectifier has a leg that's gone 'bi-directional'. Basically, when a diode fails, the stator is 'trying' to be an electric motor that has no hope of spinning its armature (in this case the crankshaft). I bet that stator cover gets pretty hot if you leave the key on for even a short time. Start there.. see what happens.

TwoTired · « **Reply #9 on:** October 24, 2011, 09:57:56 PM »

The stator and rectifier are not in the fuse circuit, so won't cause fuse issues.

You will probably need a new fuse block. Clips need clean contact and strong clamp pressure (you should need a tool to pry out the fuse from the clips.
Further the clips need to "float" so they will self align with the end caps. When they become rigidly held in place they only make contact at the diagonal points which is a pretty small contact area. Running 10 amps through a small contact area creates heating.

You never said "where" the fuse is "blowing". If near the center of the fuse span, then the fuse in seeing a true over current condition. If the fuse is melting near or under the end caps, then it is getting external heat beyond what is created running the fuse near its rated value.

Cheers,

singedebile · « **Reply #10 on:** October 25, 2011, 12:31:03 PM »

interesting point about the clips needing to float, makes sense. Maybe there is no other electrical issue (like my suspicions about the ground wire) that could be causing it, maybe its just in the block.

the fuse definitely melts.. the filament stays intact and this yellowish 'glue' seeps from the end, even had a fuse or two where the cap fell off when i took the fuse out.

Thanks, I will likely get a chance later tonight to work at it.

racemx51 · « **Reply #11 on:** October 26, 2011, 05:50:13 PM »

I was just gonna say, why dont you just start by seeing if a power wire is grounding.. Ive had just happen before too and all it was was the indicator lights touching together and blowing the system.. Start with the dumbest thing you can think of first.. Thats usually what it is haha

singedebile · « **Reply #12 on:** October 27, 2011, 05:42:26 PM »

so to check if the power wire is grounding I would unplug it at both ends then test to see continuity between it and ground?

racemx51 · « **Reply #13 on:** October 27, 2011, 06:34:17 PM »

To be perfectly honest, to see if its grounding, all I ever do if I have that happening is start it up or atleast have the key on and start moving around all your wires and see if it blows out. Take a quick look around for bare wires also. If it happens really randomly though, like, you ride the bike a week and all of a sudden the fuse blows, its probably not a short.. Mine was every time I turned my bars right it blew...
Another thing I wanted to mention was, I have a 20 amp in mine, maybe a 15 just isnt enough to support whatever you have on your bike..

HondaMan · « **Reply #14 on:** October 27, 2011, 09:18:30 PM »

Try this:
Fire up the bike, run it at 3000 RPM for about 15 seconds with the lights on, and touch the clips on the main fuse. Be careful: they might be getting hot. If so, you need a new fuseblock.

Not to sound like an ad, but I make ones that fit these bikes, which use modern automotive fuses. Drop me a PM if interested, or go to my website to see one (website in my signature, below). If you order one there, specify if the block's white connector on your bike has BLADES or RECEPTACLES in it: I have to make one up to match. Also please mention SOHC4.net if you do: you get a discount (either at order time, or via a partial Paypal refund) and the SOHC4 site gets $1 for your effort.

singedebile · « **Reply #15 on:** October 29, 2011, 02:47:28 PM »

I just realized, there is one thing that is not stock on my bike. It has Accel brand coils.. after seeing the resister pack HondaMan sells it made me thing this may be part of the issue. I can see myself buying a fresh fuseholder soon either way, but i wanted to first rule out the possibility it may be something else before I risked melting a new one.

thrutheframe · « **Reply #16 on:** October 29, 2011, 05:41:33 PM »

Quote from: singedebile on October 29, 2011, 02:47:28 PM

I just realized, there is one thing that is not stock on my bike. It has Accel brand coils.. after seeing the resister pack HondaMan sells it made me thing this may be part of the issue. I can see myself buying a fresh fuseholder soon either way, but i wanted to first rule out the possibility it may be something else before I risked melting a new one.

Hondaman is by far more qualified to comment on an issue like this than me but try metering the supply side of your main fuse to the frame, use the continuity or ohms scale. It should NOT beep if you're using the continuity scale, on ohms the meter should read infinity or I... some read 1 with no decimal for no continuity. Also meter your coils across the primaries, a low ohm situation there can cause some serious hot wires and blown fuses as well. I just went through this exact issue with my K4 also with Accel coils.

Spanner 1 · « **Reply #17 on:** October 29, 2011, 08:19:15 PM »

single... you prolly have 2 ohm coils which draw more than 2x times the power of stock coils = blown fuses unless your wiring is in pristine new condition

... why did ya change your coils BTW ?

scottly · « **Reply #18 on:** October 29, 2011, 08:21:09 PM »

Quote from: singedebile on October 29, 2011, 02:47:28 PM

I just realized, there is one thing that is not stock on my bike. It has Accel brand coils.. after seeing the resister pack HondaMan sells it made me thing this may be part of the issue. I can see myself buying a fresh fuseholder soon either way, but i wanted to first rule out the possibility it may be something else before I risked melting a new one.

The coils aren't the problem; if they drew too much current, the fuse would blow before the fuseholder melted. They may cause other issues, but your fuseholder is toast, and needs to be replaced.

Spanner 1 · « **Reply #19 on:** October 29, 2011, 08:28:14 PM »

The steady higher load of 2 ohm coils would for sure melt the fuseholders, rather than blow the fuse IMHO... those 2 ohm coils are pulling 6 amps as against stock 2.4 amps ( when 'on' )..... that is if the coils are actually 2 ohms, we don't know yet, I'll admit ! Does the OP know ??

scottly · « **Reply #20 on:** October 29, 2011, 08:42:32 PM »

Quote from: Spanner 1 on October 29, 2011, 08:28:14 PM

The steady higher load of 2 ohm coils would for sure melt the fuseholders, rather than blow the fuse IMHO

The fuseholder can only melt due to a poor connection, which is what generates the heat.

Spanner 1 · « **Reply #21 on:** October 29, 2011, 09:13:13 PM »

Yes, and a greater load over the same poor connection would not hasten the melting? The point is ; can the poor connection support the load that is demanded across it ( stock load might work merrilily away fo years ), but increase the load = trouble.

scottly · « **Reply #22 on:** October 29, 2011, 09:26:08 PM »

True, a greater load would accelerate the heating. My concerns with low ohm coils would be the points, the kill switch, and the ignition switch. The latter two can be overcome with a relay, and the points with ballast resistors.

Spanner 1 · « **Reply #23 on:** October 29, 2011, 09:33:57 PM »

We will have to wait for the OP to respond about his Accel coils.... pity he didn't mention the mod. from stock in his first post !, esp. if their 2 ohm coils !

TwoTired · « **Reply #24 on:** October 30, 2011, 10:35:52 AM »

Quote from: scottly on October 29, 2011, 08:42:32 PM

Quote from: Spanner 1 on October 29, 2011, 08:28:14 PM
The steady higher load of 2 ohm coils would for sure melt the fuseholders, rather than blow the fuse IMHO
The fuseholder can only melt due to a poor connection, which is what generates the heat.

Technically, this is not true. Consider this:

The fuse link is a metal alloy of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics.
The cross section of the fuse link is sized so that it generates internal heat based upon current flowing through.
Ergo, a fuse passing current beyond its rating generates enough internal heat within the link the melt the metal alloy.

Passing ANY current within the fuse link generates some heat relative to the amount of current passing through the link.

Let's say the fuse link melts at 600F. If you run the fuse slightly below the rating, it may attain 500F, and this heat will be radiated and conducted to any path available; end caps, fuse clips, and wire connection and also into the surrounding atmosphere.

Normally, the main fuse runs at about 10 amps which is about 2/3 of the fuse rating. It will run warm (won't burn your thumb), but still below fuse melting temperature and also below the temperature where the plastic melts.

Run a 15 amps fuse at 14 Amps, and the fuse link gets very near its melting temp., perhaps 400F-500F which is conducted to the fuse clips and sufficient to melt most plastics (and blister thumbs).

I do agree that the stock fuse block in the stock bike is normally damaged by poor or deteriorated connections. However, when electrical modifications are made to the bike, don't be surprised if the stock engineering of the electrical system can't handle additional loads placed upon it.
Certainly 3 ohm coils qualify as and electrical modification, as would higher watt headlights, heated vests, beer coolers, and hip-hop thump boxes.

Cheers,

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Author Topic: Main fuse melting (Read 5077 times)