Own a Motorcycle? Add a Multimeter to Your Toolbox

Now that life is getting back to something approaching normal here, let me tell you about my latest escapade chasing electrical gremlins – and how they could sneak up on you, too.

Most of you guys may remember that I’ve got a 1994 Sportster that has been running an upgraded wiring harness from a DOA 1995. To be honest, I did the work so long ago, I can’t tell you the ins and outs of the swap, but suffice to say, it hasn’t ever been “stock” but it has always been better than the original.

A couple of weeks ago, after navigating a particularly rough patch of road, I noticed that the left turn signal wasn’t working. I made a mental note to change out the bulb and later that day, swapped it out when I got home. Since I was in a hurry, I didn’t check my work and went on into the house.


Next time I was on the scoot, guess what? No turn signal.

Checked the seating of the bulb and it still didn’t work. My next thought led me to grounds. Nope. All good.

I snatched up the multimeter and checked the “new” bulb and it was fine. Checked for power at the switch. Got it. Checked for continuity at the plug. Got it. Checked the continuity at the ground. Got it.

Frustrated, I started tugging on wires.

Bingo! The ground continuity disappeared.

Now, some of you guys are going to proclaim that I was using those silly little butt connectors and the wire pulled out. Nope – every connection on this bike is soldered and sealed with heat shrink.

Over the years, though, the solder joint failed. What people smarter than me call a “cold solder joint.” The result was sporadic connection and over the years, it just finally gave out. I took a couple of minutes and re-soldered the connection, put some new heat shrink on it, and it was good as new.

The downside was that I started thinking – a dangerous thing for me – and the next night, I took my trusty multimeter and began checking for voltage drop across circuits on the bike. The result was pretty astounding – I found five different spots that were in danger of failing… and one was the headlight circuit. All of them bad solder joints. Now, I’ll take a connection that lasts – literally – for decades, but it opened my eyes to the fact that stuff we’ve “fixed” can still go bad.

The moral of the story? For an hour of your time and a $20 multimeter from the store, you can find issues in the electricals before they are issues. With so many newer bikes depending more on a healthy electrical system to run stuff that bikes have never had before, this might be a critical part of your winterizing process this year.

So what exactly is the problem? Simple – electronics rely on a certain amount of voltage to run them. If they have a “bad” ground, poor connection, or corrosion, this increases the resistance of the circuit and may lead to a blown fuse, fusible link, or tripping breaker. And you sitting on the side of the road cussing.

Take an hour and check out the system, clean your grounds and add a healthy shot of dielectric grease to conenctions. Remember, if your bike shows up at the stealership, they are going to charge you by the hour to track down the problem – or worse, throw parts at it until it works right.

Neither is easy on your checkbook.

Keep the shiny side up!

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