Blown fuses, tip to diagnose

This might be common knowledge already, but I'll throw it out as it helped me. I was riding home the other night and thought dang these headlights plain suck. No wonder because it wasn't lit at all, no high or low beam. I go ahead and ride home in the dark and find I have a blown 10a fuse, check out everything, find no shorts, put a fuse in and get my lights back. Ride around and it seems ok. Next day blown again so there's a problem, intermittant as always.
Here's the tip. Remove the blown fuse. Get a spare headlight and wire one of the filiments across the fuse clips temporarilly with jumper wires. Turn on the key and lights and hook a meter across the added headlight. The meter should read around 6v and be dimly lit as well as the lights the fuse protects lit dimly. If the light is full brightness there is a direct short somewhere, however this is doubtful because the short will normally be intermittent and not show up right away. Watch the meter or preferably have a meter that measures min/max with a beeper and start wiggling wires ect. When the short happens the meter reading will rise steeply. I wiggled all the wiring going in the handlebars ect and got nothing to change, then wiggled wiring in the headlight shell and the meter beeped and showed voltage had jumped to 9v. So I know my short is in the shell. So find the offending wire and all done with no more blown fuses. These AGX fuses are hard to find anymore and no use blowing anymore until the problem is fixed.

Good tip.

I'm going to switch from my stock glass fuses to the blade style the automobiles use.

Iv'e found some sources for the fuse holders(blade style) if people are interested in this let me know and I'll post the web sites. This won't be a drop in modification and drilling and tapping might be required along with some wiring changes but as the man said finding the older fuses is going to be next to impossible soon.

Fuse blocks are nice, here's mine with spare fuses; or they can be used for extra circuits, like the WG coil relay or a horn relay.




You also can cut out the fuse clips and solder this $2 fuse holder in place. It also holds the new fuses. You need one for each fuse.

RonKZ650 wrote:

These AGX fuses are hard to find anymore and no use blowing anymore until the problem is fixed.

I know what you mean Ron, lost my tail light the other day and found a blown fuse. I work as a mechanic in a fully stocked repair facility so figured no problem. Surprise!, all we had was the longer fuses, was really surprised. I'll have to change over to blade type. Question is.... the regular blade fuses or the newer mini blades?? :blink:

MFolks - I'm interested if you've found a source for the fuse blocks. I'm also with Blue Meanie, the mods I've seen have had the standard size fuseblades. I'm curious if the mini-blades would work.

One source is at www.waytekwire.com models #46070 for 4 fuses,#46071 for 6 fuses,#46082 for 8 fuses,#46083 for 10 fuses, and #46073 for 12 fuses. These blocks take the ATO/ATC type fuses.

The mini fuse blocks part numbers are:
#46090 for 4 fuses,#46091 for 6 fuses,#46092 for 8 fuses and #46093 for 10 fuses.

This company also sells all kinds of electrical devices like switches,wire,splices,heatshrink tubing,relays etc...

I'd imagine that www.delcity.net would also carry the ATO/ATC fuse holders along with the mini fuse holders.

The connections for the wire to the fuse blocks look like the standard 1/4" wide faston or quick connect type you push on the male part of the fuse block.


Make sure when wiring you use a high quality crimper as a poor crimp will get moisture and corrosion and resistance in it and the bike will run poorly if at all.

Thanks MFolks, that gives some options. I'm a litte worried about using the 46071 and 46091 'cause it's saying max 15 amps per slot and the main is a 20 amp fuse. Any thoughts? Looks like there's a heavy duty one available.

Link14 wrote:

Thanks MFolks, that gives some options. I'm a litte worried about using the 46071 and 46091 'cause it's saying max 15 amps per slot and the main is a 20 amp fuse. Any thoughts? Looks like there's a heavy duty one available.

Noticed and was wondering the same thing! :blink:

It's rated for 15A current. Although we use a 20A fuse, current draw will never be 15A on a motorcycle.

I have recently experienced the same problem with my KZ550 LTD. I blew a headlight and checked the voltage at the battery it was 21 volts. I bought a new rectifier/regulator and installed it and now it is at 13.5 volts at idle. I replaced the fuse and replaced the headlight and still the headlight does not turn on. I was wondering if anyone had any other ideas on what could cause my headlight not to work?

Remove the headlight from the shell, take an ohmmeter and continuity check the bulb. If it checks o.k. then the problem could be in the wiring,headlight switch,or fuses.

The older glass type fuses can fail and look o.k. and the only good check is to remove them one at a time and again use a continuity checker(meter or continuity light) to determine the condition of the fuse.