1100 SERIES DIESEL TRUCK ENGINE Electrical System Caterpillar

Electrical System
1.1. Solenoid Check
2.1. Starting Motor Circuit Check

The following topics describe care and maintenance of the electrical system components. These components functioning together produce the energy needed for operating the electrical equipment on the truck and each is dependent upon the other for satisfactory operation. In the event of failure or improper operation, it is essential to check the entire electrical system as a defect in one component can cause damage to another.

Many electrical system problems can be traced to loose or corroded connections. Keep connections tight and make sure the wiring insulation is in satisfactory condition. Most of electrical system testing can be performed on the vehicle. (It should be remembered, if a malfunction is found on a vehicle test, the component may need further testing, repair or replacement.)

NOTE: Installations will have electrical components not furnished by AVSpare. Consult the vehicle manufacturer's manual for maintenance procedures.

Check the electrolyte level of each cell and the general condition of the battery. Maintain the electrolyte level to the base of each vent well. The make-up water must be one of the following (in order of preference):

1. Distilled water.
2. Odorless, tasteless drinking water.
3. Iron free water.
4. Any available water.

------ WARNING! ------

Never add acid or electrolyte.


CLEANING BATTERY: Mix a weak solution of baking soda and water. Be careful not to get cleaning solution into battery. Apply the solution with a soft bristle brush.


Thoroughly rinse the battery and battery tray with clean water. Apply grease to the battery cable clamps and terminals and to all threads.

Testing The Electrolyte Solution: The general condition of a battery can be determined by measuring the specific gravity of the electrolyte solution and adjusting the reading to 80°F (27°C). If the electrolyte level is too low to allow taking a hydrometer reading, add make-up water to the correct level and then charge the battery 2 to 4 hours before taking a reading.


1. Insert the hydrometer into a cell. Fill the hydrometer barrel while holding it vertically. The float must not drag on the wall of the barrel.
2. Read the hydrometer:

1.250 or above - fully charged battery cell

1.250-1.225 - full to half charged battery cell

1.225-1.150 - half to low charged battery cell

Below 1.150 - dead cell

1.000 - water

3. Test each cell in the same manner.
4. If there is more than .050 (50 gravity points) variation between the highest and lowest reading, the battery may need to be replaced.
5. Adjust the readings to 80°F (27°C).
a. For every 10F° (5.5C°) the electrolyte temperature is above 80°F (27°C), add .004 (4 gravity points) to the specific gravity readings.
b. For every 10F°(5.5C°) the electrolyte temperature is below 80°F (27°C), subtract .004 (4 gravity points) from the specific gravity reading.

The corrected reading is of most importance during cold weather when the hydrometer reading is always corrected to a lower specific gravity reading. A low reading signifies the battery has less available power to crank the engine and that booster batteries may be required.

Voltage Test (After Load): A load test should be made on a battery that discharges very rapidly when in use. To do this apply a resistance of three times the ampere/hour rating of the battery across the battery main terminals. Allow the resistance to discharge the battery for 15 seconds and immediately test the battery voltage. A 6 volt battery in good condition will test 4.5 volts; a 12 volt battery in good condition will test 9 volts and a 24 volt battery will test 18 volts.

Use a D.C. voltmeter to locate starting system components which do not function.

Solenoid Check

Turn the key switch to START. Starting motor solenoid operation is audible as the starter motor pinion engages with the ring gear on the engine flywheel. The solenoid operation should also close the electric circuit to the starting motor.

Starting Motor Circuit Check

Attach one voltmeter lead to the solenoid terminal that is connected to the starting motor. Ground the other lead. Turn the key switch to START and observe the voltmeter. A battery voltage reading indicates the malfunction is in the starting motor. It must be removed for further testing. No voltmeter reading indicates that the solenoid contacts do not close. The solenoid must be repaired or the starter pinion clearance should be adjusted to .36 in. (9,14 mm).

A starting motor solenoid that will not operate may not be receiving battery current. Attach one lead of the voltmeter to the solenoid battery cable connection. Ground the other lead. No voltmeter reading indicates a faulty circuit from the battery.

No periodic service is indicated for the electric starter brushes between general reconditioning periods. The brushes should be inspected after removal of the starter from the engine and removal of the commutator end bearing frame. The electric starter commutator end and drive end bearings are equipped with wicks for lubrication purposes. The wicks should be saturated with oil whenever the electric starter is removed or disassembled.

It is suggested that cleaning and reconditioning be entrusted to your authorized dealer.

Drive Belts: Every 6000 miles examine the drive belts for cracks, breaks and worn areas. Replace if they show signs of wear.

NOTE: If one belt in a set requires replacement, install a new matched set of belts. If only the failed belt is replaced, the new belt will carry all the load - as it will not be stretched as much as the other belts and all the belts will fail in rapid succession.

Adjustment: Check new belts after the first 500 miles and every 6,000 miles thereafter for adjustment. To check belts, apply 25 lbs. (11,5 kg) force midway between the pulleys. Correctly adjusted belts will deflect 1/2 in. (12,5 mm) to 3/4 in. (19 mm) for new belt first check. Maintain later adjustments at 7/8 in. (23 mm).


To Adjust: Loosen mounting bolts, locknut and adjusting bolts on appropriate adjusting unit. Turn adjusting nuts to increase or decrease alternator belt tension.

If belts are operated too loose they will slap causing unnecessary wear to the belts and pulleys. Belt slipping may cause the alternator, water pump and air compressor to operate at a below normal rate and possible failure to the system.

If belts are too tight, unnecessary stresses are placed upon the pulley bearings and belts which will shorten the life of both.