85 K100 RT - Blowing horn fuse

Paswonky · Jun 7, 2013

Something odd has happened recently. Just put in a new battery, and the bike has been running fine. Now it has started to blow the fuse to the horn. and the directionals cut out, as well. I replace the horn fuse (only one blown), and it works for awhile, but then cuts out later on the road. Any hints as to what to look for?
Thanks to all who reply!

98lee · Jun 7, 2013

That fuse controls the horn, the turn indicators, emergency flashers, and the optional anti-theft system. You have a short in one of those systems.

Try turning on the blinkers in your garage and see if the fuse blows.

Try turning on the emergency flashers and see if the fuse blows.

If you don't have the anti-theft system, try pulling the horn relay and see if the problem goes away.

If you have the anti-theft system, unplug it.

:dance

pglaves · Jun 7, 2013

I am on the road so don't have manuals or schematics, but on the K75s the cooling fan is on the same fuse as the horn. It might be on your K100. If so, and if the fan has stuck, it will blow the fuse every time the fan tries to come on if there is an unblown fuse in the circuit.

You should check the schematic, and/or manually see if the fan blade turns freely when you spin it by hand.

98lee · Jun 7, 2013

As usual, Paul is right on the money. I was looking at a poor quality schematic that the lines from page to page didn't line up as well as they could. :banghead

After checking my other schematics, all two valve Ks have the fan and the horn on the same fuse.

I would put money on Paul being correct as to your problem, a frozen or shorted fan motor. Try spinning the fan blade. If there is any noticeable drag, that's almost certainly the problem.

:dance

Paswonky · Jun 8, 2013

Checked it.........

Thanks you guys - always willing to provide a head scratcher......

I went out this morning and put in a new fuse. Directionals and horn work fine. Very tight quarters to put a hand in there and reach the fan on an RT, but I was able to put a finger in there and it spun easily.

I replaced this fan last summer. bought from Euro-Motoelectrics.

Keep testing?

beachguy · Jun 8, 2013

I had the same problem 2 years ago on a trip through Central America on my K75. Finally found the problem to be a set of running lights which were wired through the horn fuse.

The poorly wired lights had a wire that was pinched by the fuel tank and kept blowing the fuse. Wasn't important though, who needs a horn in Mexico anyway?

98lee · Jun 8, 2013

Well, then the troubleshooting tips in post #2 still apply.

Add to those letting the bike idle for about 10 minutes until the fan comes on. Let fan run for maybe 2 minutes to see if it blows the fuse. Try not to let it idle so long that the overtemp light comes on.

Basically you first need to determine which circuit is blowing the fuse (ie. horn, blinkers, fan), then go from there.

:dance

85 K100 RT - Blowing horn fuse

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