Short Circuit

Yesterday I took the Speedmachine out for the second time with the new lighting system. Everything worked great for the first half hour, then I noticed the low battery light was on. Then it went off, then on again. It seemed that every time I went over a bump the battery OK and low battery lights would flicker. So I turned the system off and headed home.

As soon as I took the cover off of the main module I knew something was wrong — I could smell burned insulation. One of the four current limiting resistors for the turn signals was fried. Hmmmm... what could cause that to happen?

Aha! After some investigation I found that a component lead on the main circuit board had come into contact with one of the power switch terminals. This effectively applied 12 Volts across a 12 ohm 1/2 watt resistor. This works out to 12V/12 ohms = 1 amp x 12V = 12 Watts. No wonder the resistor fried. I replaced the resistor with a new one and added a piece of insulation to avoid a repeat performance.

Today's ride was uneventful and everything worked perfectly. After using all the lights for an hour the battery voltage is 16.31V (14.8V is about half and 12V is empty).