Section 5.Troubleshooting

Electric Motor Tests

Open Circuit Motor Test

An open circuit is one where the electrical circuit within the motor has been broken. This can be caused by:

•Bad brushes or brush springs

•Broken wire in the field or armature winding

•Loose or bad connection

Refer to Figure5-3 for the following procedure:

1.Isolate the motor from the lift truck circuit by removing the power cables. Use two wrenches to avoid twisting the terminal stud.

2.With the motor at room temperature, connect the leads of a digital ohmmeter between the individual circuits in the motor.

3.You should observe the following measurements:

Model 5200 High-Level Orderpicker

5.If you find an 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, an 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

To test for a grounded motor, see “Shorts to Frame” on page5-2.

Short-Circuited Armature or Field Winding

A short circuited winding is one where the insulation on the field or armature has broken down at 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 an increase in the current flow. The severity of the short circuit depends on its location.

A shorted motor may be indicated by:

•Slow or sluggish operation

•Running faster than normal (suggests a short in the field)

•Overheating

•Blowing a power fuse

•Burning of brush wires

4.If the meter indicates high resistance in the armature, check the condition of the brushes before replacing the motor.

•Severe burning or discoloration on the armature coil

•Severe burning or discoloration on one or two commutator segments every 90° of rotation

Publication Number: 1043922B, Revised: 2 Sept 2015

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 correctly

•Rail guided with drive tire not aligned correctly

Testing a motor for short-circuited windings requires special equipment at a motor rebuilding facility.

Publication Number: 1043922B, Revised: 2 Sept 2015

Section 5.Troubleshooting

Contactors

Contactors Testing Resistance

Visually inspect the contactor for any signs of burning or physical damage.

1.Turn the key switch OFF and disconnect the battery connector.

2.Disconnect the two wires marked X and Y contactor.

3.Connect one lead of the ohmmeter to X contactor lead and one to the Y contactor lead.

4.The reading should be between 20 and 40 ohms. If resistance is outside that range, replace the contactor.

Model 5200 High-Level Orderpicker

Fuses Test/Inspection

Examine the fuse for signs of overheating, discoloration, cracking, or other physical damage. You should be able to see if the fuse is blown through the fuse window. Replace the fuse if you find damage.

To test a fuse, remove it or isolate it from the electrical circuit. Do this by removing the fuse from the lift truck or by removing all the connections from one side of the fuse.

Use an ohmmeter set to Rx1 scale and measure the resistance across the fuse. The resistance should be less than 1 ohm.

FuseAmpsLocationFunction

FU115 Steer/Tractor Manager Control fuse for B+PC

FU215 Steer/Tractor Manager Control fuse for B+

FU3350Contactor/Fuse PanelPower fuse for TM

FU440Contactor/Fuse PanelPower fuse for SM

FU5350 or 500 Contactor/Fuse PanelPower fuse for Lift Pump Motor

FU72CarriageControl fuse for RF Terminal B+ (10 Amp Option)

FU82CarriageControl fuse for RF Terminal B– (10 Amp Option)

FU96CarriageControl fuse for Lights & Fan B+

FU106CarriageControl fuse for Lights & Fan B–

FU1110Aux Power Fuse PanelControl fuse for Carriage Heater (CS Option)

FU1210Aux Power Fuse PanelControl fuse for Tractor Heaters (CS Option)

FU1310Aux Power Fuse PanelControl fuse for Carriage Heaters (CS Option)

FU142Aux Power Fuse PanelControl fuse for GM, B+ ESTOP (WG Option)

FU1510Aux Power Fuse PanelPower fuse for Aux Power B+

FU1610Aux Power Fuse PanelPower fuse for Aux Power B-

FU1710Aux Power Fuse PanelPower fuse for Aux Power B+

FU1810Aux Power Fuse PanelPower fuse for Aux Power B-

5-14

Publication Number: 1043922B, Revised: 2 Sept 2015