Alternator for car

Follow these simple recommendations in order to avoid premature breakdown of this component:

• Try to avoid deep puddles or reduce speed before driving through them. Moisture coming to the component can cause its breakdown.
• When cleaning the space under the bonnet, protect the alternator and other electrical components from water with a polyethene film.
• Clean the unit with compressed air during every scheduled engine maintenance.
• Check and adjust tensioning of the V-ribbed belt regularly.
• Use a torque wrench for tightening fasteners.
• Avoid installation of additional equipment to protect the car’s electrical system from overloading.

The first step of checking the unit is to assess its condition visually. Its casing should have no cracks and dents, and its belt should not have critical abrasions and damaged parts. There should be no bent wires and sparks in places of their connection to the terminals.

The next step is to measure the voltage on the battery terminals, for which you’ll need a multimeter. It should be 12,5–12,7 V with the engine off, and 13,8–14,5 V with the running engine and all electrical components turned off. Under the load, with the air-conditioning system, headlights, the heater, and window heating turned on, it should be no less than 13,7–14,0 V.

If any malfunctioning takes place, remove and disassemble the component. You can estimate the wear degree of the brushes by checking their height, and of the contact rings by assessing their diameter. Measure the resistance of the rotor and stator winding and the diode bridge to define whether there is an open circuit. Compare the received data with those specified in the vehicle’s technical documentation.

The procedure can differ for cars of various makes and models. It mostly depends on the arrangement of the components under the hood. For instance, on some cars, the unit can be accessed after opening the hood, while on others – from under a lifted car. Usually, the replacement requires the following steps

1. Disconnect the negative terminal from the battery.
2. Remove the components blocking access to the alternator.
3. Remove the drive belt.
4. Take a photo of or mark the wires to avoid mistakes during reassembling. Disconnect them.
5. Unscrew all fasteners and remove the unit.
6. Install a new part.
7. Inspect the belt and pulleys visually. Replace them if necessary.
8. Connect all contacts and install the removed components back to their places

The alternator repair consists of replacing the contact rings and brushes, bearings, freewheel clutch and diode bridge. If you have experience in such repairs, you can do this yourself. Otherwise, seek assistance from a car workshop electrician.