Chapter 10 Electrical accessory and instruments

SECTION 1. GENERAL DESCRIPTION

The basic electrical system of tractors consists of the engine cranking system ,battery charging system,lighting system,meters,switches,etc. For further information concerning the engine cranking equipment and battery charging equipment, please refer to the engine manual. The battery is a power source to activate the engine cranking system,lighting system,and other electrical equipment.The lighting system is used to activate the illumination lights,indicators,and signal lights.The meter is a device that enables the operator to be aware of the present operating conditions;oil pressure gauge,water temperature gauge(thermometer),fuel gauge,etc.are installed. All the controls,meters, and indicators are arranged around the operator’s seat for easy Maneuverability readability,and convenience.

SECTION 2. SPECIFICATIONS

1.1 INSPECTION OF ELECTROLYTE LEVEL

As the battery repeats charging and discharging during operation.The water content in the electrolyte gradually evaporates, and as a result,the level should be inspected at the specific level;replenish with distilled water.

Note: a.Temperature correction of the hydrometer reading

When the distilled water is added,charge the battery to mix it well into the electrolyte before measuring the specific gravity.

The specific gravity of the battery electrolyte(diluted sulfuric acid) varies with the temperature of the electrolyte at a rate 0.0007 specific gravity point for each 1℃ change in temperature.Therefore, when the specific gravity of the electrolyte in the battery is measured with a suction type hydrometer,a temperature correction should be made,using the following formula to permit the direct comparison of the measured valve with the standard specific gravity at 20 ℃

S20 :St+0.0007(t-20)

S20 :Specific gravity at standard temperature of 20 ℃ t : Temperature of the electrolyte at the time of measurement

St : Specific gravity of the electrolyte measured at t ℃.

1.2 INSPECTION OF ELECTROLYTE SPECIFIC GRAVITY

The specific gravity of the electrolyte lowers as the battery discharges,so the battery condition can be determined by measuring the specific gravity.The specific gravity can be measured generally with a suction type hydrometer which must be read properly as shown in Fig. 10-2

1.3 BATTERY CHARGING

If the specified gravity of the battery electrolyte in lower than 1.220 (at 20 ℃),the battery should be recharged,because leaving an undercharged battery without recharging it will lead to permanent battery damage.The battery is subject to self-discharge at a rate as shown in the table below.Therefore it should be recharged from time to time when storing the battery unused for a long period of time.

When recharging the battery,wash clean the outside of the battery case and the battery posts.Check the level of the electrolyte in each cell and replenish with distilled water as necessary.