Section 5. Troubleshooting
Toyota Orderpicker Model 7BPUE15 Service Manual
Electric Motor Tests 3. YOU should observe the following
measurements: Motor Drive Motor
Probe Points
1
S1 to S 2 (shunt)
1
1
Resistance 0.9 to 1.5 ohms
Short-circuited Armature or Field Winding
1 insulation A short rirclriterl winding is one in which the on the field o; armature has broken
A2 t o S l ; A 2 to
> 100,000
down a t two or more points. The breakdown creates a low resistance path, allowing current to flow from one turn of the coil to another adjacent coil turn, without actually flowing through the coil wire. The result is a decrease in total resistance of the motor winding and a n increase in the current flow. The severity of the short circuit depends on its location.
A1 o r A 2 to Frame
> 100,000
A shorted motor may be indicated by:
S1 to S 2
< 1 ohm
A1 to A2
< 1 ohm > 100,000
A1 to S 1 ; A1 to
1
ohms
< 1 ohm
Lift Motor A to Frame
> 100,000
A1 o r A2 to Frame
> 100,000
Steer Motor
4. If the meter indicates high resistance in the armature, check the condition of the brushes before replacing the motor.
5. If you find a n open circuit in a series-wound motor, the motor must be disassembled by a motor rebuilding facility to isolate the problem to the field or armature circuit.
Grounded Motor Test In a grounded motor, a n electrical circuit exists between the current-carrying conductors and the motor housing. This can be caused either by direct contact or through conductive foreign material. The ground may be caused by: Insulation breakdown Brush leads touching the motor housing Buildup of carbon dust or other materials
Slow or sluggish operation Running faster than normal (suggests a short in the field) Overheating Blowing a power fuse Burning of brush wires Severe burning or discoloration on armature coil Severe burning or discoloration on one or two commutator segments every 90" of rotation. These symptoms can be caused by problems other than the motor itself: Brake too tight or dragging Wheel bearings too tight Faulty transmission Binding in a related pump, hose, or solenoid valve Load wheels not aligned properly Rail guided with drive tire not aligned properly Testing a motor for short-circuited windings requires special equipment a t a motor
To test for a grounded motor, see "Shorts to Frame Test" on page 5-4.
00700-CL222-05, 1 5 March 2005
