Turn/Brake circuit blowing fuses

Big Russ

Big Russ

Joined
Nov 14, 2009
Messages
12
Location
Southend, UK
Bike
ST11OOa
I need some help from any wranglers of elastic-trickery out there . Possibly a falorn hope, but if you don't ask you will never find out

My Pan had an alarm fitted to it by a previous owner which was modified by the dealer when they took it in part exchange and before I even saw it some 9 years ago

This summer I have been blowing the fuse on the Turn lights/Brake light circuit quite regularly, I blew my 4th since the beginnig of May, say over 6000 miles, which I think may be due to the insulation around the repair on the loom when they took the alarm off breaking down. The dealer has long since shut up shop, so at least to give be a chance to trace the joint down , around 12 years ago was there a favorite place to wire an alarm into the turn light circuit so the indicators flashed when the alarm was set off ?

All brake and turn lights are working normally otherwise so I don't think it is a bulb drawing too much blowing the fuse (only a 10a fitting) although I don't know if they have ever been changed so they may well be the original Honda bulbs as fitted by the factory.

Many thanks for considering this
 
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The easiest place to tap that is under the seat running along the frame rail any splice repair should be obvious by sight. Could be chaffed in that area too take a close look
 
Your theory may or may not be correct ......

Does the fuse blow when using either turn signal or just one ? Or does it blow when applying the brakes ? Or does it blow when neither the brake or turn signals are used ? I realize there is no way to answer these questions, yet. Some logical troubleshooting may be in order if your "alarm system" theory doesn't pan-out ( no pun intended ). Do you have a wiring diagram ? You can answer the questions if you would connect a test lamp/LED to the +12 volts from the 10A fuse to monitor the voltage on that circuit as you are riding down the road. Check that test lamp/LED just before applying the brakes or using the turn signals. If the fuse blows when the brakes or turn signals aren't applied, that would narrow the cause ( before the brake & turn signal switch).

I just looked at the wiring diagram - the turn signal relay ( flasher ) is fed by the +12 volts and also has a ground connection. It may be intermittantly defective & blowing the fuse, possibly. I would replace it and see if the problem dissapears. If not, you would have a spare. Good luck and have fun. Sometmies these electrical problems can be a lot of fun !!
 
Either too heavy an electrical load or direct short is what blows fuses. Assuming that the electrical load isn't too heavy that leaves the short. How to find the short? Go buy some Cracker Jax, might take several boxes until you find the compass prize:D Next connect an auto resetting circuit breaker to that circuit where the fuse is inserted. The resetting and blowing of the circuit breaker will set up a magnetic field in that circuits wiring. Hold the compass next to the wire harness and start moving it away. When the compass needle quits jumping and is dead, there is the wire break.
 
Not sure what tools you have available to you, but if it were my bike I'd start eliminating things one at a time by measuring the current draw of various items. Having never had to do this before, the first step would be to figure out how to break the circuit at the fuse to insert the meter. Probably the easiest way to do that is to take one of your blown fuses and attach lead wires to the two legs, or better yet if you can remove enough of the plastic to attach alligator clips directly to the legs with the fuse plugged into its socket.

First, I'd measure the current being drawn with no brake lights or turn signals (but the tail light and front running lights will still be on). Check the wiring diagram to see if there should be anything else on this circuit, if so you may want to check it first, but let's say for now that there's nothing else. Check the manual for the wattage of the tail and running lights, and measure the current for those items. If its excessive, pull the bulbs one at a time and see how the current changes. If there's a problem, you'll see one bulb produce more effect than the others. If the current goes to zero after all bulbs are pulled, then the excess draw is either in the bulb itself, or downstream from the bulb towards ground. If there's still residual current draw with no bulbs, check the path between the fuse and the bulb sockets. Also, disconnecting connectors in the path (if you can identify them) will also aid in narrowing down the location.

If no unexpected current is found, then try activating the brake lights next. Hit the brake lights and see what the current draw is, and compare that to the wattage specified in the service manual for the brake lights, and add that to the current expected for the tail and running lights. Not sure exactly how the brake lights work, I think the brake light is in addition to the tail running light, make sure by looking at the bulb when you hit the brakes. If this draw is higher than expected, remove the bulbs and hit the brakes again, if the current is non-zero then follow the same procedure as in the previous paragraph.

Then find the turn signal flasher if you can, in the old days they were a simple aluminum can which could be easily jumpered to turn the signal on and hold it on. Not sure what the ST uses, if its more complicated than the two terminal can you may have to get creative to figure out how to hold the turn signal filament on to take a steady reading. If you can't control it then just look at the current draw dynamically when the signal flashes and see if you can make any determination from that. Again, compare to the expected wattage for the turn signals in the manual.


edit: I have a meter that can measure up to 20A, so originally I thought that might be enough headroom to trace out a 10A circuit, but with a dead short that's probably going to blow the 20A fuse in my meter as well. Many meters only have a 10A current capability, so they would blow their fuses as well. After seeing the resettable circuit breaker mentioned in later posts, that's definitely the way to go.
 
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Next connect an auto resetting circuit breaker to that circuit where the fuse is inserted. The resetting and blowing of the circuit breaker will set up a magnetic field in that circuits wiring. Hold the compass next to the wire harness and start moving it away. When the compass needle quits jumping and is dead, there is the wire break.[/QUOTE]

Now that's absolute genius!!!
 
Hi,
So this intrigued me and I went smoking around about electrical shorts on the web. Found this youtube website about finding a short in a jeep and the guy used a neat gizmo. It uses the autoreseting circuit breaker like buddingeezer said and also used a proximity ammeter. The ammeter showed which direction the short was going. Neat!! and only about $26 on amazon... called the SG Tool Aid 25100 Short Tester

http://www.youtube.com/watch?v=TZrCrBx4uFY

There also is the ECT 2000. It's basically the same thing but ammeter has a bunch of bells and whistles.



Neat stuff...
 
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Big Russ' problem is that he has an INTERMITTANT short that is blowing the fuse. It's not there all the time. So that gizmo is a neat device to use IF the short is there ALL the time, but in his case, it won't help. BTW, a small compass would work just as good - it responds to the high magnetic field produced by a short circuit ( high current = strong magnetic field ).

Russ, as I mentioned before, temporarily install a voltage monitor in the circuit immediately after the fuse. That will give you the info. you need to logically troubleshoot your problem. You need to know if the problem is before or after the brake switch or turn signal switch ( and which turn signal, left or right ) to narrow the source of your problem.

If you want to shot gun the problem, replace the turn signal flasher and all the turn signal & brake light bulbs. Visually check the bulb sockets for frayed wires, etc.
 
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Big Russ said:
...around 12 years ago was there a favorite place to wire an alarm into the turn light circuit so the indicators flashed when the alarm was set off ?
Click to expand...
The most convenient space for placing an alarm-HU was/is the tailcone compartment. Depending on MFG/source of the alarm its wiring was either properly spliced in with a model specific Y-harness kit (i.e. the ones offered as OEM accessory by HondaLine), or were connected by cutting into the bike's harness and twisting/disarranging the strands together (worst case: wrapped with insulation tape)... in short: a mechanical damage done to the bike wiring... and my guess would be that this is causing an intermit/random short to ground/frame. So I'd pop the seat flip that grey plastic cover forward to gain access to the sockets, connector and wiring for the taillight and check for damages on the wiring there.
 
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