There is an occasional no power when key switched on. to a hotspot the immediate left of the horn. developed at a point in that panel. The wires in How should I proceed?

Your Horn relay or other relays may be bad. This forum may help as well: http://www.ramforumz.com/showthread.php?t=179545

Hi,

These problems are difficult to find, but not impossible. The wiring harness will have to checked at the following points. Check the fuse unit. (Clean all connections on the fuses and contact points.) Trace the connections from the horn to the firewall. If that is fine, check the connections from the wiper to the firewall. Inspect the wire harness loom that goes through the firewall towards the steering wheel. Inspect the "kickdown" switch underneath the accelerator. Test the switch for continuity. If the problem is still unresolved, check the relay panel and all relays for corrosion on any connectors. Be sure to inspect all earthing points on the body.(brown wire). This will take you a couple of hours to work through. Always tidy the wires after inspection and use proper solvents when cleaning contact points. I had a similar issue with my W124, when turning on the lights, the wiper started to work. I found the problem caused by a short on the headlight unit when I was working on the car. Good luck, I hope you find the problem soon.

Yes, there is a fuse panel on the bike but I think that it's on the rear fender extension on that model. But, from what you are saying, it might not be the fuse. The horn is on a fused circuit with some other stuff as well. You do not have a single fuse dedicated to only the horn. Unlike a car, there isn't enough room on a motorcycle for this. The fuse that controls the horn controls other things as well and it everything else is working, then it's not the fuse. I'd test the wire at it's other end, the horn button. When you press the button, the wire to the horn goes "hot". Years ago, the wire going to the horn was "hot" all the time and when you pressed the button, you completed the circuit to ground. It was learned that any short in the horn wire would blow a fuse or discharge the battery so the design was changed. This was way back when the bikes were powered by a 6 volt system. Take the left handle switch housing apart and check the switch.

Good Luck
Steve

I have a 1998 BMW r1100rt, my horn would not work and while messing with the system, I developed the following problem. My flashers and turn signels will not work, the turn signels on the left side will come on when I turn the key on but won't go off unless I pull the fuse. I need help, 165 miles to the shop. Thanks

The horn gets it's power from the horn fuse which is live all the time.Power goes from it to the switch and then out of the switch to the horn.Test the wire to the horn with a test light or a multi-meter and if there is no power you likely need the horn button replaced,if there is power you may need to remove the horns and clean the rust from their mounting points to get a better ground or turn the adjusting bolt on the horn until it will blow,if neither of these work you will need to buy a new horn.

Before checking the horn, I would check all of the fuses and the horn relay. If all of those are fine, on a lot of vehicles the horn is located inside either the left or right front clip. In other words, in the space between the left and right engine bay walls, and the outside of the left and right fender. You will have to remove the inside of the fender (above the wheels) to see if the horn is in there. Also, the switch inside the steering wheel could have gone out. If you can get the front panel off of the steering wheel, run a wire from the positive to negative wires on the horn switch, if the horn works, the switch has gone out.

Assuming you don't have any other problems to deal with like a bad horn relay, you would want to intercept the horn signal wire going up into the steering column and wire that to the switch such that it gets grounded by the switch when you want the horn to honk. Since a toggle switch could be left on for an extended amount of time, I would think a momentary switch of even a push button type might be a better choice?

The horn relay is used to allow for large current flow going to the horn itself without forcing that same amount of current to flow thru the horn switch in the steering wheel for example, which might be easily burnt out without the relay's buffering effects. Even a large macho toggle might not be able to handle a horn's current if used regularly. The load for a raw horn is highly inductive (arcing,sparking) in addition to being a very large current draw of 10 amps or better, both conditions tend to make kindling of everything but the most robust switches. Those switches when you do find them cost the big dollar$.

You might just need a horn relay, they do have a lot of work to do - they are allowed to wear out occasionally considering their use.

Battery Constant 12v+ Positive Wire (+): Black/Orange And Red/White
Battery Constant 12v+ Positive Wire Location: Ignition Switch Harness
Starter Positive Wire (+): Yellow
Starter Positive Wire Location: Ignition Switch Harness
Ignition Positive Wire (+): Blue (16 Gauge)
Ignition Positive Wire Location: Ignition Switch Harness
Second Ignition Positive Wire (+): Yellow/Red
Second Ignition Positive Wire Location: Ignition Switch Harness
Accessory Positive Wire (+): Blue (10 Gauge)
Accessory Positive Wire Location: Ignition Switch Harness
Second Accessory Positive Wire (+): Orange
Second Accessory Positive Wire Location: Ignition Switch Harness
Parking Light Positive Wire (+): Black/Yellow
Parking Light Positive Wire Location: At Headlight Switch
Power Door Lock Positive Wire (+): Orange/Violet
Power Door Lock Positive Wire Location: In Drivers Kick Panel, White 6-Pin
Power Door Unlock Positive Wire (+): Pink/Violet
Power Door Unlock Positive Wire Location: In Drivers Kick Panel, White 12-Pin
Door Trigger Negative Wire (-): Yellow
Door Trigger Negative Wire Location: At Headlight Switch
Domelight Supervision Wire: Use Door Trigger (Requires Relay)
Domelight Supervision Wire Location: N/A
Horn Negative Wire (-): Black/Red
Horn Negative Wire Location: At Steering Column Harness
Tachometer Wire Negative Wire (-): Gray
Tachometer Wire Negative Wire Location: At PCM, Connector 1, Pin A7. The PCM (powertrain control module) is located on the firewall next to the wiper motor.
Brake Light Positive Wire (+): White/Tan
Brake Light Positive Wire Location: At Switch Above Brake Pedal
Factory Alarm Disarm Wire (-): Black/Orange (To disarm requires a (-) negative through a 1565 ohm resistor and an extra relay to connect.)
Factory Alarm Disarm Wire Location: In Drivers Kick Panel, White 12 Pin Plug
Factory Anti-Theft System: N/A
Factory Anti-Theft System Location: N/A

Horn fuse should be labeled on the fuse block. If it's not, easiest way to check is to just check them all. Use a test light and probe the back side of each fuse on both ends, till you find one that only has power on one side. Horn works with key off but I generally check with key on. Also, you have a horn relay (should be in the power distribution center (basically another larger fuse box, usually on the right fender under the hood. If all else fails, run a "hot" wire right to the horn & make sure it works. Horn "switch" is actualliy part of the signal mechanism and internal parts within the steering column...though these sometimes develop dead spots, it's least likely that it is the source of your problem.