Troubleshooting Motors : Checking Fuses

 Initial Steps in Troubleshooting Motors:

1. Check Voltage:

   • Verify voltage to the motor.
   • If no voltage, trace the circuit backward to find the interruption (controller, starting component, blown fuse, or tripped circuit breaker).

2. Safety First:

   • Electricity can be fatal; wear conductive gloves.
   • Keep the meter in line of sight to the work area.
   • Do not move your head to see both the meter and the work.

Checking Fuses:

1. Outside Disconnect Box:

   • Use a voltmeter with power on.
   • Zero volts across the fuse indicates it is good.
   • Full circuit voltage indicates the fuse is open (bad).
   • Partial voltage also suggests a bad fuse.

2. Inside Disconnect Box:

   • Use an ohmmeter (since disconnect boxes do not open with power on).
   • Zero ohms of resistance across the fuse indicates it is good.
   • Infinite or high resistance indicates a bad fuse.

Procedure for Checking Fuses:

1. Voltmeter Method:

   • Carefully place meter leads across the fuse.
   • Zero volts = good fuse.
   • Full voltage = open (bad) fuse.
   • Partial voltage = bad fuse.

2. Ohmmeter Method (inside disconnect box):

   • Ensure power is off (handle down).
   • Use an ohmmeter across each fuse.
   • Zero ohms = path for current flow (good fuse).
   • Infinite or high resistance = bad fuse.

Additional Checks:

1. Line and Load Connections:

   • Check voltage at line connections with the power off.
   • Verify proper voltage coming in (e.g., 212 volts for a 240-volt circuit).

2. Identifying Issues Before Replacing Fuses:

   • Determine the cause of the blown fuse (grounded or shorted load).
   • Address underlying issues before replacing fuses or resetting breakers.