To test the switch, touch the test light to the switch output wire connection while moving the shift lever. The light should glow as the shift lever is slid into park or neutral. The light should not work in any other position. If the light is not working properly, check the mechanism that operates the switch. If the problem is in the switch, replace it.
The condition of the starting motor should be carefully checked at each PM service. This permits you to take appropriate action, where needed, so equipment failures caused by a faulty starter can be reduced, if not eliminated.
A visual inspection for clean, tight electrical connections and secure mounting at the flywheel housing is the extent of the maintenance check. Then operate the starter and observe the speed of rotation and the steadiness of operation. To prevent the starter from overheating, do NOT operate the starter for more than 30 seconds.
If the starter is not operating properly, remove the starter, disassemble it, and check the commutator and brushes. If the commutator is dirty, it may be cleaned with a piece of No. 00 sandpaper. However, if the commutator is rough, pitted, or out-of-round or if the insulation between the commutator bars is high, it must be reconditioned using an armature lathe.
Brushes should be at least half of their original size. If not, replace them. The brushes should have free movement in the brush holders and make good, clean contact with the commutator.
Once the starter is checked and repaired as needed, it should be reassembled, making sure that the starter brushes are seated. Align the housings and install the bolts securely. Install the starter in the opening in the flywheel housing and tighten the attaching bolts to the specified torque. Connect the cable and wire lead firmly to clean terminals.
There are many ways of testing a starting motor circuit to determine its operating condition. The most common tests are as follows:
The starter current draw test is used to measure the amount of amperage used by the starting circuit.
The starter circuit voltage drop tests (insulated circuit resistance test and starter ground test) are used to locate parts with higher than normal resistance quickly.
The starter current draw test measures the amount of amperage used by the starting circuit. It quickly tells you about the condition of the starting motor and other circuit components. If the current draw is lower or higher than the manufacturer's specifications, there is a problem in the circuit.
To perform a starter current draw test, you may use either a voltmeter or inductive ammeter or a battery load tester. These meters are connected to the battery to measure battery voltage and current flow out of the battery. For setup procedures, use the manufacturer's manual for the type of meter you intend to use.
To keep a gasoline engine from starting during testing, disconnect the coil supply wire or ground the coil wire. With a diesel engine, disable the fuel injection system or unhook the fuel shutoff solenoid. Check the manufacturer's service manual for details.
With the engine ready for testing, crank the engine and note the voltage and current readings. Check the manufacturer's service manual. If they are not within specifications, there is something wrong with the starting circuit.
Do NOT crank the engine for more than 30 seconds or starter damage can result. If the starter is cranked too long, it will overheat. Allow the starter to cool for a few minutes if more cranking time is needed.
Starting Circuit Voltage Drop Tests
A voltage drop test will quickly locate a component with higher than normal resistance. This test provides an easy way of checking circuit condition. You do NOT have to disconnect any wires and components to check for voltage drops. The two types of voltage drop tests are the insulated circuit resistance test and the starter ground circuit test.Continue Reading