Design and technical characteristics of electrical equipment (Mercedes-Benz E-Class W123)

Contents: Battery ↡ Generator ↡ Starter ↡ Lamps used in cars, W: ↡ Battery maintenance ↡ Tightening torques of main threaded…↡

The electrical equipment is 12-volt, with negative terminals to ground. The battery is recharged by an alternator with a belt drive and a built-in voltage regulator.

Pre-engaged starter: The traction relay engages the pinion gear with the ring gear before voltage is applied to the starter motor.

This section provides repair methods, although in some cases it is more profitable to completely replace units with worn-out components.

Every 16,000 km, check the operation of all electrical equipment units and the electrolyte level in the battery. Top up the electrolyte if necessary. At the same time, check the wear of the windshield wipers and replace them if necessary.

Electrical equipment type: 12V, negative terminals to ground.

Battery

Characteristic	Meaning
Capacity, A.h	55

Generator

Characteristic	Meaning
Type	Bosch 55A or 65A
Charging current at engine speed, A
engine M 123.920	36 at 1040 rpm, 55 at 3130 rpm
engine M 123.921	36 at 930 rpm, 55 at 2760 rpm
engine M 110 (until March 1980.)	36 at 1040 rpm, 55 at 3130 rpm
engine M 110 (since March 1980.) with 55 A generator	36 at 930 rpm, 55 at 2760 rpm
engine M 110 (since March 1980.) with 65 A generator	43 at 980 rpm, 65 at 2760 rpm
Minimum permissible brush height, mm	5

Starter

Characteristic	Meaning
Type	with preliminary engagement
Power, kW	0,85; 1.04 or 1.5

Lamps used in cars, W:

Purpose of the lamp	Meaning
Headlight bulbs (halogen)	60/65
Fog light bulbs (halogen)	55
Direction indicator lamps	21
Direction indicator and front parking light bulbs	21/5
Brake light bulbs	21
Reverse light bulbs	21
License plate lights	5
Rear side light bulbs	10
Front Parking Light Bulbs	4
Rear fog lamps	21
Interior lighting lamps	10
Glove box lighting lamps	5
Trunk lighting lamps	10

Battery maintenance

The standard battery has an automatic device to prevent electrolyte overflow. If the electrolyte level is below the upper mark on the front side of the battery, remove the filler plugs or cover and add distilled water until the cavities above the rubber plugs begin to fill with water (see Fig.). At this level, the cells are filled and the plate separators are covered with electrolyte.

Keep the top surface of the battery clean to prevent dust and moisture from accumulating on it, which will cause partial self-discharge of the battery over time.

Check the brackets and the battery mounting area for corrosion. If traces of corrosion are found, remove the battery, remove the corrosion products, treat the affected surface with an appropriate anti-corrosion compound and apply a coat of paint of the original color.

Every time you remove the battery, check it for cracks and leaks. Cracks can appear in winter when adding distilled water after driving, and not before leaving. In this case, the water, which has not had time to mix with the electrolyte, freezes and breaks the wall of the battery tank. Cracks in the tank can be sealed with an appropriate compound, but this depends on the material of the tank. If electrolyte leaks from one of the battery cells, fill it with fresh electrolyte.

An excessively high electrolyte level with an intact battery tank indicates that the battery is overcharged and the voltage regulator may be faulty.

If the car has a low annual mileage, it is recommended to check the density of the electrolyte every three months to determine the battery charge level. To check, use a hydrometer inserted through a rubber stopper, comparing the results obtained with the data below:

Characteristic	Meaning
Ambient temperature 25°C
full charge	1,270—1,290
70% charge	1,230—1,250
full discharge	1,110—1,130

It should be remembered that the hydrometer is calibrated for an electrolyte temperature of 15°C. Therefore, subtract 0.007 from the measured value for every 10°C below 15° and add 0.07 for every 10°C above 15°C.

If you are suspicious about the condition of your battery, first check the specific gravity of the electrolyte in each cell. A difference of 0.040 or more between any cells indicates electrolyte loss or deterioration of the plates.