How to solve your own electrical mystery, or assist others on this forum in helping you.
I have written the advice below because I find myself repeating the same things over and over either in person or on the net when trying to help people with bike/car electrical issues.
Automotive electrical problems can be tricky to diagnose and can cause you to throw tools across the garage, kick things, and unleash torrents of abuse all over your pride and joy. There are not many things in the world worse that waking up to a nice sunny Saturday morning, getting geared up and jumping on the bike, only to find she won't start, indicators don't work, there's a funny burning plastic smell, or some other electrical fault has developed.
While mysterious gremlins sometimes seem to have crept in to the garage in the middle of the night, there is always a logical explanation for whatever has happened, even if it doesn't seem like it at the time.
Following a few simple troubleshooting steps will help you solve the problem quicker, possibly cheaper, and with less frustration than attacking it willy-nilly. It will also mean that other people can help you without sending you in totally the wrong direction or asking "have you tried this and that".
To that end, here's my initial thoughts for basic steps - these may need editing or adding to over time:
1. Capture the fault
Finding out exactly when the fault happens is a big first step. Find out what happens, when it happens, if it is repeatable, and everything you notice that happens at the same time.
BAD: "I think my battery is faulty"
GOOD: "Every time I try to start the bike, whether it's hot or cold, raining or sunny, weekday or weekend, it seems to crank over slowly. I have also noticed that the headlight is not very bright, and my indicators seem to be flashing slower than they used to."
2. Mention the last work that was done on the bike
If 2 days before the fault started, the bike got a new battery or the alternator was replaced - this is useful information to know. Mention anything that was done recently, even if it is not obviously electrical system related.
Some people are surprised to find for example that getting exhaust work done on your bike can cause an indicator to stop working. Why? Because (this is just a hypothetical example) when the exhaust guy does some welding on the pipework, he will disconnect the battery earth first. During the welding something happens to the indicator circuit like a spark hits an exposed wire and melts the insulation from a section, the bike gets wheeled past something that snags a wire, or any of a number of other things that cause the indicator circuit to be shorted.
When the battery is reconnected, the indicator fuse blows and this doesn't get noticed because the exhaust guy doesn't test ride the bike, he just starts it and checks for gas leaks and so on.
BAD: "My indicators don't work, I have replaced the fuse but it keeps blowing"
GOOD: "My indicators don't work, I have replaced the fuse but it keeps blowing. The bike has had a new exhaust system put on it a couple of days ago, could this have anything to do with it?"
NOTE: no recent work is still valid to mention. What I mean is that if the last time the bike was serviced in any way was 30 years ago, that gives us clues about looking for things like corrosion, seized solenoids and relays etc.
3. Check the charging system and battery
Any electrical system troubleshooting is a complete waste of time if you can not guarantee that the charging system/battery is good. You can waste a lot of time looking for a fault that only exists because the charging system is not working properly - you might take apart most of the ignition wiring looking for why you have a weak spark, when all you had to do was tighten the battery connections. Make it easy on yourself and check the charging system first.
The battery health is closely related to the health of the charging system - a fault in one can affect the other. A common example is a battery going faulty, then the owner replacing it - only to find that the battery was killed by a faulty charging system and the new battery gets killed as well, leaving you out of pocket for ANOTHER poked battery plus whatever time/money it takes to fix the original fault!
The attached chart is simple to use, and even if you don't have any reason to suspect a charging problem, run through it, because if there really is no problem, the chart ends after 3 steps.
Note that the first step is to start with a charged battery - even if you have previously checked the charging system or are troubleshooting something unrelated, a charged battery is needed or you may get incorrect readings, things being locked out on under voltage and other issues that make it harder for you. If possible, a known GOOD battery should be used so that you are only checking the charging system, not the battery as well. If you then put the original battery back into the bike and find that the tests fail, you know where the problem is.
BAD: "Help! I think my stator needs rewinding!"
GOOD: "I have run thru the chart and i end up at the "check stator" box. Can anyone advise somewhere reputable to confirm this for me?"
4. Get the right tools
If you want to solve your own problems, get a multimeter and a test light. You can buy a multimeter for $10 that is more than adequate for automotive use. You can make a test light for the cost of a spare bulb and some wire, or you can buy one in a more convenient form for a few bucks. A tiny investment in these two tools will pay you back the first time you find a simple broken wire or loose connection and fix it rather than paying the shop (which will be a bit more than the $10 or so you spent buying the tools!).
SAFETY NOTE: A cheapo multimeter is fine for automotive use - but check it's ratings carefully before playing with anything bigger, like your house wiring. The meter AND probes need to be IEC 61010 -1 cat II rated at a minimum for mains testing, and you need to know what you are doing and why.
Also, it's difficult to damage yourself or a DMM when measuring most things, with an exception being current. A common mistake is to move the probes to the current holes in the meter and put it down, then pick it up some time later and try to measure voltage somewhere. It's good practice to return the meter probes to the voltage measuring position after you measure a current to avoid this.
Useful paper from Fluke on automotive testing:
A few other bits and pieces may be needed but depends on the work you are doing. Try and use the right tool for the job - e.g. if you need to insulate something, use insulation tape, not sellotape or packing tape. If you need to replace a connector, use the right crimping tool and the right size wire.
There are good reasons for using the correct tool or part, even if they are not immediately obvious! It will just cost you more money or time when you have to re fix the fault if you don't use the right parts and tools the first time.
5. Check the common causes
Make sure all electrical connections that you can get to are clean and tight. If your battery posts are covered in green gubbins, you have blackened or melted connectors in the wiring loom, your frame and engine earth points are corroded and/or loose, or your ignition barrel is hanging half way out of the dash, fix these things first!
A lot of auto electrical problems are resolved with no replacement parts - just a good check, clean, and tighten of connectors. Switches, especially high current ones (e.g. in the starting and lighting circuits), are prone to getting burnt contacts which leads to intermittent symptoms. Switches and connectors that are exposed to the elements or can get chain oil and other contaminants in them are also prone to failing, the fix for which is nothing more than a good clean out.
Brake, clutch, indicator and starting switches are usually all on the handlebars or which means they can get moisture and dirt in them, their wires can get stretched, caught or trapped as the bars are turned, or they might simply need adjusting, as some of them are acted on by cables and levers that wear and move over time. That last point especially applies to foot brake switches and side stand switches as these get road spray and other crap in them, plus they have a large degree of mechanical movment/adjustment.
6. Swap parts out
If you have determined that a part if at fault or you have a theory, and you have access to a substitute part that is KNOWN TO BE GOOD, then swap it out. This is a common trick in eletronics servicing - you swap out parts and see if the fault follows the part or the bike (or TV or whatever you are fixing). For example, if you think for whatever reason that your battery is faulty (hopefully you have run through the cart linked to above), swap it with a known good one and see what happens (ideally you would re run the chart!).
"Known good" means just that - do not swap a battery that you have lying around of unknown origin, or one a mate has in the shed! Ideally you would get one from a shop that will allow you to return it if it turns out the battery was not the problem, but such customer service is rarely seen these days. Another idea is to borrow from a mate's bike, although the big fat warning below should be read first.
In the frustrating case where you swap parts around, then find that the original parts on the original bike now do NOT have any faults - you have disturbed either a wiring fault or a connector problem. You might have temporarily disturbed a broken or frayed wire so that it works, or it might be as simple as a dirty connector and a few plug/unplug sequences have cleaned up a bad contact.
BIG FAT WARNING: It is unlikely that swapping parts will kill the donor part, but it CAN happen! If you have applied common sense and thought about the fault then you should be safe, however as an example, I would not swap an ECU or dash module or similar delicate piece of kit into a suspect bike without being sure of what I was doing and why, and probably taking measures to protect the donor part. It is unlikely that you will kill a donor Regulator/Rectifier, battery, starter motor, alternator stator etc as these are grunty devices and will withstand some abuse, especially for short term tests.
7. Report back when it's fixed
If your thread just dies, future readers don't know if the last thing suggested fixed the problem, or if the last thing suggested turned you and your bike into a pile of ash on the garage floor. Take a minute to return the favour and post about what fixed it - this will be useful to someone else in future.
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Originally Posted by porky
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