An entertaning story of how I figured out where the wiring circuit of my headlight was failing, lacking a multi meter or continuity test light: Traveling minimalist in South America, I left my jumper wire, my continuity tester, and my multi meter at home. I hadn't needed anything like that for quite a few trips. This time, early on, my headlight failed to work. Tunnels with no lighting was the main reason motivating a fix. I don't ride at night.

How to fix: I do have an electric air pump for flats. I bought a length of wire from a moto shop and stripped the ends. Using the pump, on some tests I wanted to determine if I had good ground. Connect the hot lead side of the pump to the + battery terminal, and run my jumper wire from the ground side of the pump wire to the terminal I was testing. Pump turns on and I have ground on the terminal I was testing.

Same strategy when testing for power at the hot terminals, except the ground side of the pump now was connected to the - side of the battery terminal, and the jumper connected to the + side of the pump. Touch the + side jumper to the terminal I wanted to test, and again, if the pump made noise, I had power to that terminal.

In the end, I was able to determine that the lack of power to the headlight was in the handlebar dimmer switch, not a typical location. Opened up the switch, cleaned up the terminals, and I had a functioning headlight.

Obviously a continuity test light or multi meter would be much more helpful and easier to use, and much faster, but the pump worked to locate my problem. Desperate needs, desperate solutions. As an option to the pump, I could have used a bulb or other item from the moto to locate the fault.

Definitely a functional but unique electrical diagnostic tool.

You used the pump to provide a 'test light'/continuity tester. Provides an audio signal when continuity exists, some people use the horn for the same function.

Works for things that are robust, could not be used to check an engine temperature sensor.