Author Topic: Main fuse keeps blowing (Read 26002 times)

bozo4onion · « **Reply #100 on:** September 03, 2008, 07:52:28 AM »

+1 on corrosion. I just did that myself...... After my headlight failed for the same reason. I wrapped sandpaper around a screwdriver blade and reamed away.

TwoTired · « **Reply #101 on:** September 03, 2008, 08:10:43 AM »

When you pass current through a resistance, it generates heat. Increase EITHER resistance or current and it makes more heat.
Corrosion/oxidation, even if it is transparent, is resistive. Adding brighter headlamps, draws more current.

The fuse is designed to melt with a set current passing through it. Lesser currents still generate heat, just not enough to melt the fuse material.
The stock bike draws about 10 amps through the 15A fuse. This creates about 1/2 to 2/3 of the heat needed to melt the fuse. It will be warm to the touch, but not painful. However, add resistance heating from fuse clips and/or more current passing through fuse and fuse clip oxidation and the fuse gets much closer to the temp needed to melt the fuse element. This is often a big ouch for human fingers.

Another issue is fuse clip contact pressure on the fuse. Generally speaking, the more contact pressure, the more the two metal parts behave as one piece of metal, offering lower resistance for electricity to traverse the region between the two metals.

The clip therefore, must hold the fuse tightly. You should not be able to remove the fuse with bare fingers. But, rather pry out with a tool or better yet, require a fuse extractor made for that purpose.
The fuse clip retention springing can be damaged by excessive or repeated heating of the clip material, as this "relaxes" the metal. Often, though, you can regain strong fuse retention by pinching the clip ends together.

The fuse block can also get hot enough to lose solder on the connections at the back. Lost solder means higher resistance and the heat from this can also conduct toward the fuse clips/fuse.

Finally, the fuse clips must be allowed to float in the fuse block. This allows them to self align with whatever fuse is installed and present the most contact area between fuse and fuse clip. More area of contact equals lower resistance. If the plastic where the fuse clips attach to the block is melted, this alignment ability is usually compromised.

Each one of these factors can contribute a small amount to the problem. However, a large amount can be created from many small amounts.

Cheers,

beelsamin · « **Reply #102 on:** September 03, 2008, 08:22:26 AM »

Thank you very much gentlemen,going through every connector and cleaning them and touching up with dilectric grease was on my list but I keep putting it off...time consuming and beer consuming..............

andy8190 · « **Reply #103 on:** March 16, 2009, 05:35:27 PM »

so i just redid the headlight bucket wiring and everything seems to be working ok but when i turn the headlight on it blows the main fuse, does anyone know what this could be from?
1974 cb550

andy8190 · « **Reply #104 on:** March 16, 2009, 05:39:25 PM »

i did put 16 gauge wire splices on instead of 18 gauge, would that make a difference?

Spanner 1 · « **Reply #105 on:** March 16, 2009, 05:40:54 PM »

What kind of boik?

andy8190 · « **Reply #106 on:** March 16, 2009, 05:44:47 PM »

what kind of what?

SKTP · « **Reply #107 on:** March 16, 2009, 05:46:12 PM »

Double check everything...I had a similar problem turned out, I had an obvious green goto to brown or some other combo that was blowing the fuse whenever I hit the front brake...

Spanner 1 · « **Reply #108 on:** March 16, 2009, 05:47:04 PM »

Thats how the Brits pronounce ' bike ' !!!...ohoh, I'm in for it now !

andy8190 · « **Reply #109 on:** March 16, 2009, 05:50:36 PM »

where should the blue, white, and green wire go in relation to the 3 prongs on the headlight?

Spanner 1 · « **Reply #110 on:** March 16, 2009, 05:55:54 PM »

Eh, what bike is it ,'cos there is a difference.

andy8190 · « **Reply #111 on:** March 16, 2009, 06:04:47 PM »

its a 1974 cb550k

TwoTired · « **Reply #112 on:** March 16, 2009, 06:06:55 PM »

What size fuse are you blowing?

andy8190 · « **Reply #113 on:** March 16, 2009, 06:09:58 PM »

15amp

Spanner 1 · « **Reply #114 on:** March 16, 2009, 06:10:34 PM »

Sorry, I don't have a wiring diagram for the 550...except to ask, does the fuse blow with the h/l unplugged ?
Any 550 guys ?

andy8190 · « **Reply #115 on:** March 16, 2009, 06:33:19 PM »

sorry for the delay, i had to go buy more fuses. let me try that hi/lo trick

andy8190 · « **Reply #116 on:** March 16, 2009, 06:36:14 PM »

ok just tried the head light with just the white and green plugged in and blew another fuse, and then tried with just the blue and the green plugged in and blew a fuse.

andy8190 · « **Reply #117 on:** March 16, 2009, 06:37:34 PM »

could it be a connections from the wires i spliced together somewhere? i am so confused by this

andy8190 · « **Reply #118 on:** March 16, 2009, 06:48:14 PM »

does it matter if the numbers going to the 2 black wires in the main harness are not exactly like stock. Say instead of 4 black wires going to one of the main black wires and one going to the other i have like 3 going to one black wire and 2 to the other? and same for the green wires?

scartail · « **Reply #119 on:** March 16, 2009, 07:02:00 PM »

My understanding is.. no... all the greens go to together, etc. Just make sure that all the colors you are bundling is indeed that color. ie. some of the turn signal lines use black, but at the end, they have an orange or blue collar.

I have a 550 as well, and I keep blowing fuse when i made extreme turns... It turn out that i was shorting out my lines (pulling them together when i was turning, doh!)... The point is... don't ignore the obvious or the unquestionables.

good luck.

ps... do you have this trouble if you leave the head lamp off, and switched between hi/low?

MikeB · « **Reply #120 on:** March 16, 2009, 07:02:40 PM »

wow that sounds confusing
do you have an ohm meter if so check for continuity between your headlight socket
should be infinite res. between green and the other 2

maybe see if it blows the fuse with the light unplug and you switch the light on
could be your switch shorting out

also check your headlight see if it's
shorted out (not very likely, normally they blow open) you never know

Mike

andy8190 · « **Reply #121 on:** March 16, 2009, 07:05:17 PM »

ok let me plug everything back up and try it without the headlight actually in. i shouldnt have soldered connections touching anywhere bc i shrink wrapped them all.

andy8190 · « **Reply #122 on:** March 16, 2009, 07:17:30 PM »

ok i have the turn signals unplugged as well as the headlight and turned the headlight switch on and no blown fuse. will progress from here.

andy8190 · « **Reply #123 on:** March 16, 2009, 07:25:35 PM »

YES. turns out the wires going into the headlight needed to be rearranged, ground is not where the plastic piece is labeled

andy8190 · « **Reply #124 on:** March 16, 2009, 07:35:50 PM »

wait i was wrong, the headlight works but when i put the blinker back on it shorts out. so must be the blinkers right?

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Author Topic: Main fuse keeps blowing (Read 26002 times)