Fuses limit the amount of current or energy that can travel through them before they open and disconnect the circuit from the energy source (battery). They have a rating on them specific to their location and they should never be replaced with one of greater value or damage to the harness, fuse holder, and outbound electrical circuit/device can occur.
Fuses open because the potential energy used was greater than the rated value. Usually do to shorts, pinched wires, bare wires, or faulty components like a voltage regulator going bad and internally the electronics short to ground. In this example, you likely can't see it but you could measure it with an Ohm meter.
Typically water ingress is not enough to blow a fuse. Meaning you can hose down an exposed 12V circuit and it will continue to work. However as the water has more impurities its resistance goes down. If it gets low enough, it can impair the circuits operation. Do NOT confuse this low voltage with the energy in the ignition system which is much higher depending on the stage. The primary side which feeds the ignition coils 12.0 - 400volts. The Secondary side which fires the spark plugs 20000 to 50000volts. Here water can impair the operation if there is fault in the insulation.
Back to ways to troubleshoot:
1) isolate what happens/doesn't happen. Usually the fuse does this for you
2) when does it happen
3) what changed, it used to work and now it doesn't. Why?
4) print the schematic for your bike!!! With this, you can track down everything the fuse does. From this, you may notice you played a hand in the 1, 2, and 3 parts above but hopefully not!
5) tools;
If a fuse opens repeatedly, don't just keep replacing the fuse. Find the source of the issue. A good way to troubleshoot a circuit is to build a basic tester with a lamp. You need:
Remove the blown fuse and insert the spade connectors into the fuse pocket (fuse removed). If the circuit is ON all the time regardless of ignition switch AND the circuit has a short after the fuse, the light will light indicating current is flowing. The brighter the light, the closer the circuit is to a dead short which is what is blowing the fuse.
If the circuit is only hot when the key is on, the test light will come on when the ignition is turned on.
Options: using the schematic as a guide unplug connectors in that circuit. When the light goes out, you found the branch that is shorted to ground. Keep looking until you find the actual fault. This may include unplugging another component and testing it for a short using an Ohm meter.
Look up the component and see what its supposed to measure. It will help you understand if its OK or defective.
That's it for now.
Fuses open because the potential energy used was greater than the rated value. Usually do to shorts, pinched wires, bare wires, or faulty components like a voltage regulator going bad and internally the electronics short to ground. In this example, you likely can't see it but you could measure it with an Ohm meter.
Typically water ingress is not enough to blow a fuse. Meaning you can hose down an exposed 12V circuit and it will continue to work. However as the water has more impurities its resistance goes down. If it gets low enough, it can impair the circuits operation. Do NOT confuse this low voltage with the energy in the ignition system which is much higher depending on the stage. The primary side which feeds the ignition coils 12.0 - 400volts. The Secondary side which fires the spark plugs 20000 to 50000volts. Here water can impair the operation if there is fault in the insulation.
Back to ways to troubleshoot:
1) isolate what happens/doesn't happen. Usually the fuse does this for you
2) when does it happen
3) what changed, it used to work and now it doesn't. Why?
4) print the schematic for your bike!!! With this, you can track down everything the fuse does. From this, you may notice you played a hand in the 1, 2, and 3 parts above but hopefully not!
5) tools;
- tools - your eyes are #1. Follow the trail from the fuse to the device using the schematic. Look for abrasions, wear, pinch, burns - both internal from a short or external like the exhaust, insulation missing, bare wires, connectors exposed, etc. strain where something was pulled apart. . .
- tools - volt meter, use this to determine potential for a component to work. If for example you measure the systems battery voltage and it shows 12.8 volts and then measure the exposed contact on the fuse top, one side shows 12.8v and the other side shows 0.0v then you know the fuse is blown.
- tools - ohm meter, these are great for determining if a component has potential to work. For example a typical switch will be open in one position measuring infinite ohms i.e. greater than a million and the other position should measure less than 1 ohm or effectively a dead short.
- tools - 12v automotive test light. Across a 12v battery they light brightly. Across a dead unpowered circuit they don't light. You can substitute incandescent lamps if you have a holder to connect to them.
- tool - service manual. The service manual provides specifications for components and sometimes specific steps and how to troubleshoot problems. Its very helpful! Get IT!
If a fuse opens repeatedly, don't just keep replacing the fuse. Find the source of the issue. A good way to troubleshoot a circuit is to build a basic tester with a lamp. You need:
- Wire (16 - 18 gauge)
- Male spade connectors, non-insulated for 16 - 18 gauge wire dia.
- Alligator clips with boots for 16 - 18 gauge wire dia.
- Electric tape // just so there is no exposed wire, clamps etc
- 12v test lamp
- crimping tool and wire strippers
Remove the blown fuse and insert the spade connectors into the fuse pocket (fuse removed). If the circuit is ON all the time regardless of ignition switch AND the circuit has a short after the fuse, the light will light indicating current is flowing. The brighter the light, the closer the circuit is to a dead short which is what is blowing the fuse.
If the circuit is only hot when the key is on, the test light will come on when the ignition is turned on.
Options: using the schematic as a guide unplug connectors in that circuit. When the light goes out, you found the branch that is shorted to ground. Keep looking until you find the actual fault. This may include unplugging another component and testing it for a short using an Ohm meter.
Look up the component and see what its supposed to measure. It will help you understand if its OK or defective.
That's it for now.
