SENR9977 59 Testing and Adjusting Section Voltage drops that are greater than the amounts in Table 10 are caused most often by the following conditions: The voltage at the battery post is within 2 volts of the lowest value in the applicable temperature range of Table 9. Loose connections The large starting motor cables get hot. Corroded connections Use a suitable ammeter in order to measure the current. Place the jaws of the ammeter around the cable that is connected to the “bat” terminal. Refer to the Specifications Module, “Starting Motor” for the maximum current that is allowed for no load conditions.
Faulty switch contacts Diagnosis Procedure The procedures for diagnosing the starting motor are intended to help the technician determine if a starting motor needs to be replaced or repaired. The procedures are not intended to cover all possible problems and conditions. The procedures serve only as a guide. The current and the voltages that are specified in the Specifications Module are measured at a temperature of 27°C (80°F). When the temperature is below 27°C (80°F), the voltage will be lower through the starting motor. When the temperature is below 27°C (80°F), the current through the starting motor will be higher. If the current is too great, a problem exists in the starting motor.
Repair the problem or replace the starting motor. Note: Do not crank the engine for more than 30 seconds. Allow the starter to cool for two minutes before cranking the engine again. If the starting motor does not crank or cranks slow, perform the following procedure: If the current is within the specification, proceed to Step 3. 1. Measure the voltage of the battery. 3. Measure the voltage of the starting motor. Measure the voltage across the battery posts with the multimeter when you are cranking the engine or attempting to crank the engine. Do not measure the voltage across the cable post clamps. a.
Use the multimeter in order to measure the voltage of the starting motor, when you are cranking or attempting to crank the engine. a. If the voltage is equal or greater than the voltage in Table 9, then go to Step 2. b. If the voltage is equal or greater than the voltage that is given in Table 9, then the battery and the starting motor cable that goes to the starting motor are within specifications. Go to Step 5. b. The battery voltage is less than the voltage in Table 9. c. The starting motor voltage is less than the voltage specified in Table 9. The voltage drop between the battery and the starting motor is too great. Go to Step 4.
A low charge in a battery can be caused by several conditions. Deterioration of the battery A shorted starting motor 4. Measure the voltage. a. Measure the voltage drops in the cranking circuits with the multimeter. Compare the results with the voltage drops which are allowed in Table 10. A faulty alternator Loose drive belts Current leakage in another part of the electrical system b. Voltage drops are equal to the voltage drops that are given in Table 10 or the voltage drops are less than the voltage drops that are given in Table 10. Go to Step 5 in order to check the engine. 2. Measure the current that is sent to the starting motor solenoid from the positive post of the battery. c.
The voltage drops are greater than the voltage drops that are given in Table 10. The faulty component should be repaired or replaced. Note: If the following conditions exist, do not perform the test in Step 2 because the starting motor has a problem.