Cautions In Event Of Blown Fuse

When a fuse is blown, there are two probable causes. One is that it is blown due to flow of current exceeding its rating. The other is that it is blown due to repeated on/off current flowing through it. Which of the two causes is responsible can be easily determined by visual check as described below.

1. Fuse blown due to current exceeding rating

   The illustration shows the state of a fuse blown due to this cause. In this case, do not replace the fuse with a new one hastily since a current heavy enough to blow the fuse has flowed through it. First, check the circuit for shorts and check for abnormal electric parts. After correcting shorts or replacing parts, use only a fuse of the same capacity as a replacement. Never use a fuse of larger capacity than the original fuse. If a larger capacity fuse is used, electric parts or wiring could be damaged, or could start a fire.

   Fig 1: Identifying State Of Fuse Blown Due To Overcurrent

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
2. Fuse blown due to repeated turning current on and off

   The illustration shows the state of a fuse blown due to repeated current on/off. Normally, this type of problem occurs after a fairly long period of use and is less frequent than above. In this case, simply replace with a new fuse of the same capacity.

   Fig 2: Identifying State Of Fuse Blown Due To Thermal Fatigue

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.