Alternators Damage Scenarios

Alternators Damage scenarios

MAHLE Aftermarket GmbH Causes, remedies, and avoidance Pragstraße 26 – 46 70376 Stuttgart /Germany Phone: +49 711 501-0 www.mahle-aftermarket.com

www.mpulse.mahle.com mahled-089/04.2020/EN 02 03

Preface Contents

MAHLE is one of the most important develop- The same high quality guidelines are also applied to spare parts Design and function of an alternator 04 5 Function ment partners and manufacturers of engine com- for the aftermarket. ponents and systems in the automotive industry. 5.1 No alternator function Numerous checks during and after production ensure the con- 1 Ingress of liquid (defective excitation diodes) 20 The engineers at MAHLE develop products of sistently high quality level of MAHLE products. If, however, 5.2 No alternator function the highest quality throughout the world in con- unexpected failures occur in practical operation, the causes are 1.1 In the alternator 06 (defective rectifier diodes) 22 junction with engine and vehicle manufacturers. usually to be found in the engine environment. Operating or 5.3 No alternator function assembly errors, or unsuitable operating media, may also be with connection for battery sensor 24 2 Assembly errors causes of failure. 5.4 No alternator function after a certain mileage 26 2.1 Belt pulley I 08 This brochure summarizes typical damage scenarios, describes 2.2 Belt pulley II 10 their causes, and provides tips for avoiding similar damage in the 2.3 Regulator 12 6 Performance future. This makes it easier to troubleshoot potential causes of 2.4 Electrical connection 14 damage. The advice provided in the brochure helps to ensure 6.1 No alternator output, that our products work reliably in the long term and thus prolongs rotor makes grinding noise 28 the engine service life. 3 Contamination 6.2 No alternator output, battery charge indicator does not go out 30 Furthermore, our experts are also confronted with complex dam- 3.1 Heavy contamination in the alternator 16 age scenarios that go beyond the scope of this brochure. In cases

where damage to our products cannot be readily diagnosed, we Glossary 32 4 Mechanics are more than willing to examine them at our premises and put together an expert damage report for you. Please contact your 4.1 Mechanical damage to the alternator 18 Our product portfolio 34 local sales partner.

Our information services 35

Info at:

www.mahle-aftermarket.com 04 05

4 5 4 6 7

Design and function 1 2 3 of an alternator

Many of the functions in a vehicle require electrical power. A bridge rectifier with high-power diodes is used to convert the When the combustion engine is running, this is generated by alternating current. The exciter coil in the rotor receives the nec- the alternator. In contrast, the car battery serves as a power essary power from the regulator, depending on the vehicle’s store and buffer. current power requirements. The regulator supplies the rotor via carbon brushes that press against the slip rings on the rotor. The construction of the alternator must be designed to ensure that sufficient power is available for all electric components that As a result of electromagnetic losses and the electrical resis- are operated over a long period of time. It is also important to tances of the components, heat is generated in the alternator take into account the customary engine speeds. in addition to electrical output. Depending on the design, one or two fans are therefore installed on the rotor shaft to dissipate The alternator is usually driven by the vehicle engine via a belt. heat. In the alternator, the turning of the rotor in the stationary stator generates electrical current inductively. Most alternators are three-phase alternating current generators.

(A) 120 14 V 120 A

110 12 11 10 9 8

100 14 V 95 A 90 Regulator 14 V 85 A 80 14 V 80 A

70 14 V 70 A

40 1 Belt pulley 7 Rectifier/excitation diodes

30 2 Distance washer 8 Regulator/carbon brushes/slip rings U = const. = 13 V Tamb. = 23°C ± 5°C 20 3 Shaft 9 Rear bearing

10 4 Fan 10 Rotor 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 5 Housing 11 Stator n/rpm 6 Protective cover 12 Front bearing Example connection diagram Alternator characteristic curves 06 07 Ingress of liquid Ingress Findings: n Brush abrasion as a paste in the n Leak in the engine, hydraulic system, 1.1 Ingress of liquid vicinity of the regulator or fuel system

n Alternator oily on the outside n Brush holder charred n Alternator contaminated during (engine/hydraulic oil or diesel fuel) filter change In the alternator n Alternator provides little or no output n Contamination occurred when filling Cause(s): the engine with oil n Increased brush wear n Thermal overload of the alternator, n Heavily worn slip rings n Ingress of liquid in the alternator grease leak from the alternator Assembly errors (engine/hydraulic oil or diesel fuel) bearings

- Remedies /avoidance: Contamination n Replace alternator. n In the case of heavy exposure to n Connected electric components dust and dirt: clean air inlet, fan, must match the alternator out- n Find and remedy cause of leaks in and alternator regularly. put voltage. If additional electric the oil, hydraulic, or fuel system. components are connected,

choose an alternator that is iden- tical in construction but with a higher output level, if required. Mechanics

Very oily slip rings Oily regulator Caution! If there is leakage oil in the engine compartment, do not use flammable liquids to clean the alternator: this poses a fire hazard! Function

Very oily alternator Very oily alternator Oily regulator with sticky carbon abrasion Oil in the alternator Performance 08 09 Ingress of liquid Ingress 2.1 Assembly errors Findings: Cause(s):

n Thread of shaft damaged/torn off n Belt pulley nut tightened with an excessively high tightening torque Belt pulley I (shaft overloaded at thread)

n Belt pulley nut tightened in an uncon- trolled manner with an impact wrench Assembly errors

- - Remedies /avoidance: Contamination n Replace alternator. n Tighten belt pulley nut with the prescribed torque: n Fasten shaft with a suitable hex key M16 × 1.5: 95 Nm ± 5 Nm, or polygon head wrench. M27 × 1.5: 152 Nm ± 17.5 Nm

Caution! Mechanics Never use an impact wrench to tighten the belt pulley nut. An impact wrench may only be used to loosen the nut. Before adjusting the nut, check the direction of rotation! Function

Thread on generator shaft heavily damaged Remnants of the torn-off shaft in the nut Generator shaft torn off as a result of an excessively high tightening torque (impact wrench) Performance 10 11 Ingress of liquid Ingress Findings: n Shaft heavily worn in the vicinity of n The mechanic screwed the over- 2.2 Assembly errors the front ball bearing running alternator pulley onto the shaft without the necessary dis- n Alternator provides no output after n Rotor has touched the stator tance washers. As a result, the a certain mileage Belt pulley II n Grinding marks on the rotor inner ring of the roller bearing was n Noise in the alternator not fastened tightly enough to the n Some of the stator laminations have shaft. The shaft rotated in the inner n Battery charge indicator lights up shifted circumferentially, causing bearing ring, causing it to become a short circuit in the windings n Belt pulley loose worn. Because of the increased play Assembly errors between the bearing ring and shaft, n Traces of wear on the belt pulley Cause(s): the rotor was not guided cleanly n Thread on the shaft heavily and was grinding against the stator. worn/abraded The laminations in the stator were n Nut was not fastened tightly enough displaced from one another, causing n Rotor has significant radial clearance on the shaft. As a result, the belt short circuits in the windings. on the belt pulley side pulley was loose and was spinning on the shaft.

- - Remedies /avoidance: Contamination

n Replace alternator. n When assembling a belt pulley, n Tighten belt pulley nut with the place the appropriate distance prescribed torque: n Fasten shaft with a suitable hex key washers underneath. M16 × 1.5: 95 Nm ± 5 Nm, or polygon head wrench. M27 × 1.5: 152 Nm ± 17.5 Nm Mechanics

Clearly visible wear of the shaft in the vicinity of the ball bearing (nut was loose). Clearly visible wear of the shaft in the vicinity of the bearing (nut was loose). As a result of the increased play, the rotor has ground against the stator.

Grinding marks on the stator caused by the rotor as a result of shaft wear Shaft end heavily worn by belt pulley (nut was loose) Function

Overrunning alternator pulley assembled without distance washer Alternator with overrunning alternator pulley assembled by customer Shaft end heavily worn by belt pulley (nut was loose) Shaft heavily worn in the vicinity of the front ball bearing (nut was loose) Performance 12 13 Ingress of liquid Ingress Findings: n Score marks and burning marks n Because the contact surface 2.3 Assembly errors on a slip ring of the broken-off carbon is too small and there is too little con- n Immediately or a short time after a tact pressure: heavy sparking new regulator is installed: battery occurs on the affected slip ring Regulator charge indicator lights up (no output) Cause(s):

n Immediately after a new regulator n When the regulator is disman- is installed: low alternator output tled or assembled: carbon

n Coarse fracture structure on has caught and broken off Assembly errors carbon (forced rupture), some light n Broken carbon transmits only a run marks from the slip ring in the low excitation current: alterna- center of the broken carbon tor provides little or no output

- - Remedies /avoidance: Contamination n Replace alternator. n When dismantling or assembling the n If the carbons catch, do not use regulator, press carbons against the force. spring force into the regulator to prevent the carbons from catching. Mechanics Function

Slip rings damaged by broken carbon Carbon broken off during dismantling/assembly of the regulator Carbon broken off during dismantling/assembly of the regulator Performance 14 15 Ingress of liquid Ingress Findings: Cause(s): n If nuts are not correctly tightened or 2.4 Assembly errors become loose, contact resistances will lead to increased component n Vehicle battery not sufficiently charged n Nut not fastened tightly enough temperatures and electric arcs at B+ Electrical connection n Nut of connection B+ loose resulting from the charging currents n Connection cable not fastened n Terminal stud B+ thermally discolored according to manufacturer specifi- n Terminal stud B+ partially burned cations; freely swinging cables can lead to loosening of the nut n Nut and washer show burning marks Assembly errors

and melting

- - Remedies /avoidance: Contamination n Replace alternator. n Fasten connection cable according n Tighten nut with the correct torque: to the vehicle manufacturer specifi- M5: 3.3 Nm ± 0.6 Nm n Examine connection cable and cations in order to prevent the cable M6: 5.1 Nm ± 0.9 Nm cable grip for damage and replace from swinging freely. M8: 11 Nm ± 2 Nm if necessary. M10: 11.8 Nm ± 2.3 Nm Mechanics

Nut not fastened tightly at connection B+ Function

Burning marks on washers and nuts Cable grip with burning marks Burnt connection B+ (enlarged) Performance 16 17 Ingress of liquid Ingress Findings: n Alternator is heavily contaminated n Alternator is contaminated with 3.1 Contamination on the outside liquids (oils, fuel, coolant, leaked bearing grease), which also means n Alternator provides insufficient or n Heavy contamination and incrustations, increased adhesion of dust no output including on the inside of the alternator Heavy contamination in the alternator n Reduced heat dissipation as a result n Alternator is making noises n Diodes are damaged of adhesion of dust and contami- n Ball bearing is running rough nants: thermal overload and damage to the components in the alternator n Insulation on the copper windings Cause(s): Assembly errors and cables in the alternator are n Thermal overload of the ball bearing: thermally discolored reduced load-bearing capacity of n Heavy contamination from dust or the lubricating film; leaking grease n Carbon brushes and slip rings are contaminants from the environment can damage the ball tracks heavily worn for the mileage

- - Remedies /avoidance: Contamination n Replace alternator. n In the case of heavy accumulation of n In the case of contamination dirt during operation: clean alternator from liquids: determine cause and engine compartment thoroughly and remedy leaks. at appropriately short intervals.

Caution!

If there is leakage oil in the engine compartment, do not use Mechanics flammable liquids to clean the alternator: this poses a fire hazard! Badly clogged alternator Dirt in the stator windings Function

Badly clogged rectifier and excitation diodes Discolorations and score marks resulting from dirt on the slip rings of the Heavy contamination on the regulator Carbon overheated and blocked in the melted guide alternator Performance 18 19 Ingress of liquid Ingress Findings: n Alternator provides little or no Cause(s): 4.1 Mechanics output or voltage

n No function n Regulator housing broken n Alternator was damaged during transport Mechanical damage to the alternator n Damage to plastic cover n Grinding noises when the belt pulley is rotated manually n Alternator was dropped n Bent electrical connections during installation n Alternator doesn’t run smoothly n Electrical connections broken off n Alternator has knocked against n Alternator is blocked n Defective parts and components other components in the engine Assembly errors inside a damaged plastic cover compartment

- - Remedies /avoidance: Contamination n Do not throw or drop the alternator. n If the alternator is damaged, n When fitting the alternator, secure do not install it; otherwise, it initially with at least one bolt so n Always check the packaging and follow-up costs may be incurred. that it cannot fall during installation. alternator for damage prior to fitting. n When fitting the alternator, avoid n Rotate alternator shaft manually and knocking it against other components check for noises or stiffness. in the engine compartment.

Mechanics

Alternator housing cover broken Mechanical damage to the power diode and plastic holder Function

Laminations inside the stator displaced Deformation (dent) in the stator (e.g., due to alternator being dropped) Condenser connection broken off Regulator housing deformed and cracked Housing cracked as a result of mechanical (e.g., as a result of alternator being dropped) (mechanical overload) overload Performance 20 21 Ingress of liquid Ingress 5.1 Function Findings: Cause(s):

n Alternator provides no output n Short circuit in the cable connection No alternator function (defective excitation diodes) n Battery charge indicator lights up n Connection polarity reversed n Excitation diodes melted and/or n Short circuit with other components cracked in the engine compartment

n Melting and erosion marks resulting n Short circuit with tools Assembly errors from electrical sparking on the regula- n Battery disconnected while engine tor housing, alternator, or connections is running

- - Remedies /avoidance: Contamination n Replace alternator. n Before working on a car body n Always ensure correct polarity using electric welding equipment, when using starting aids. n Always disconnect the battery always disconnect the battery. before working on the alternator. n Never disconnect the battery while n Disconnect the battery when the engine is running (overvoltage). n Ensure connection cables have connecting fast charger. correct polarity. Mechanics

Traces of arcing on alternator housing Burnt excitation diode (short circuit) Function

Burning marks on alternator housing due to short circuit Live wire causes short circuit in regulator Signs of short circuit on the ground terminal and on the regulator housing Performance 22 23 Ingress of liquid Ingress Findings: Cause(s): n Diodes overloaded by excessive 5.2 Function current

n Alternator provides insufficient n Battery connection polarity reversed or no output No alternator function (defective rectifier diodes) n Reverse polarity at connections n Connections on one or more B+ and B – on alternator (if B – is rectifier diodes are burnt designed as a screw connection)

n Rectifier diodes allow no flow n Fast charging unit incorrectly

in either direction connected or voltage spikes Assembly errors

n Rectifier diodes allow flow in n Reverse polarity when using both directions starting aids

Power diode connection melted as a result of short circuit Burnt copper power rail Performance 24 25 Ingress of liquid Ingress 5.3 Function Findings: Cause(s):

n Alternator provides no output n Sensor cable for battery mon- itoring was not connected to n Battery charge indicator lights up No alternator function with connection for battery sensor the alternator (S terminal)

n Battery sensor defective

n Break in sensor cable

Assembly errors n Short circuit on sensor cable

n Alternator is not intended for this application

- - Remedies /avoidance: Contamination In certain applications, a sensor monitors connected at all, the output of the alter- n Check battery sensor cable. the battery temperature. If the battery nator is reduced to zero by the regulator. n If there is no battery sensor in the temperature is too high, the alternator vehicle, install another suitable alter- output is throttled to prevent damage. n Connect battery sensor. nator (correct alternator for vehicle/ If the electric resistance value of the n Check battery sensor. engine according to MAHLE catalog). sensor is too high or the sensor is not Mechanics Function

Alternator with S terminal for battery sensor Battery temperature sensor Performance 26 27 Ingress of liquid Ingress Findings: Cause(s): n Heavy vibrations in the engine due 5.4 Function to a defect in the injection area

n Battery charge indicator lights up n Heavy vibrations in alternator due n Defective overrunning alternator to loose fixing bolt pulley also causes heavy vibrations No alternator function after a certain mileage n Alternator provides no output n Heavy vibrations due to broken n Effects of vibrations: solder n Solder joint cracked inside the alternator mount joints damaged, cable breaks, alternator frayed electrical insulation n Vibrations throughout the engine n Cable break inside the alternator due to defective vibration damper Assembly errors n Short circuit in stator windings or engine mounting

- - Remedies /avoidance: Contamination n Replace alternator. n Always identify and remedy causes n Check function of overrunning of vibrations. alternator pulley and replace if necessary. Mechanics Function

Broken solder joint on alternator as a result of heavy vibrations Frayed winding insulation Performance 28 29 Ingress of liquid Ingress Findings: Cause(s): n Bearing damage due to thermal 6.1 Performance overload of the alternator; grease leaked from ball bearing, raceways n Alternator provides no output n Bearing damage due to excessive and balls extremely worn belt tension n Battery charge indicator lights up No alternator output, rotor makes grinding noise n Alternator speed too high as n Heavy vibrations on the belt tensioner n Alternator makes strange noise a result of belt pulley being too during operation n Engine running unevenly as a result small (gear ratio) of defect in injection system n Rotor shaft has a large radial clearance Assembly errors n Bearing damage in the combustion n Metallic abrasion inside the alternator engine n Rotor makes grinding noise when n Water ingress in roller bearing rotated manually

- - Remedies /avoidance: Contamination n Replace alternator. n Check combustion engine (running n Identify and remedy cause of smoothness, bearing play in the thermal load (entry of dirt, check n Use new belt and new clamping crankshaft). total connected load). device. n When washing the engine, do not hold n If the power requirements increase n Set belt tension according to manu- the jet of the high-pressure cleaner because additional components are facturer specifications. directly on the alternator. connected: choose an alternator with

a correspondingly higher output. Mechanics Function

Grinding marks on the stator caused by the rotor Overheated roller bearing; grease leak Performance 30 31 Ingress of liquid Ingress 6.2 Performance Findings: Cause(s):

n Alternator provides no output n Cable became trapped when replacing regulator No alternator output, battery charge indicator does not go off n Battery charge indicator does not go off when engine is running n Short circuit on cable D+

n Cable from D+ is pinched

n Cable insulation damaged Assembly errors

- - Remedies /avoidance: Contamination n Replace alternator. n When fitting the alternator and replacing the regulator, ensure that no electric cables become trapped. Mechanics Function

Cable from D+ trapped under regulator housing Cable from D+ trapped under regulator housing Pinched cable Performance 32 33

Glossary Glossary

Term Explanation Term Explanation

The belt pulley drives the alternator. It is important to ensure that the belt pulley is aligned with the alternator and the In principle, an alternator supplies a somewhat higher voltage than the vehicle system voltage. This is the only way the Belt pulley crankshaft. Voltage battery in the vehicle can be charged. With a 12 V electrical system, the alternator supplies 14 V. A 24 V electrical system is provided with 28 V. Burning marks Discoloration of insulation or melting of metallic components due to arcing.

The capacitor stores energy. It can temporarily absorb current and discharge it again. In this way, a capacitor can Capacitor smooth out fluctuations in voltage.

The carbon brushes transfer the field voltage from the regulator to the rotor’s slip rings. In the rotor there is a coil that Carbon brushes generates the excitation magnetic field. Both ends of this coil are connected to a slip ring.

Central nut The central nut is used to screw the belt pulley onto the shaft. The nut must always be tightened with the correct torque.

Amount of current produced by the alternator. The greater the charging current, the greater the mechanical energy Charging current required to drive the alternator. The regulator therefore adjusts the field voltage so that the alternator only produces the amount of current required by the components.

Diodes are semiconductors that allow current to flow in one direction only. They can be used in a circuit to create Diode a rectifier that converts alternating current into direct current.

To ensure the correct axial position of the belt pulley, distance washers must be placed behind the belt pulley. Distance washer It is important that the belt pulley is tensioned tightly to the shaft and the inner bearing ring of the ball bearing with the central nut.

Insulation made of synthetic resin for copper wires. Copper wires for coils usually come with enamel insulation. Enamel insulation As the insulation is very thin, more windings can be fitted into a small installation space.

Excitation diode Excitation diodes make supply voltage from all three phases available to the regulator.

In compact-diode assembly alternators, there is an external fan between the belt pulley and the alternator housing. Fan (external) The fan draws cooling air from the rear housing through the alternator. The advantage of this is that, if necessary, the direction of rotation of the alternator can be changed when using a different fan.

In compact alternators, there are two fans, one at the front on the rotor and one at the back end of the rotor. The cooling Fan (internal) air is drawn in at the front and guided radially to the stator winding.

The field voltage is controlled by the regulator. The regulator supplies the voltage to the rotor that is needed to generate Field voltage a certain excitation magnetic field strength.

The alternator housing is important for dissipating heat. Air diffusers and ventilation slots conduct the cooling air to Housing thermally critical components in a targeted manner.

Diodes designed to handle high currents. Certain power losses cause the diodes to heat up. Power diodes often have Power diode aluminum housing, which is pressed into a heat sink.

For compact-diode assembly alternators, there are special protective covers with a very fine mesh that keeps out larger Protective cover foreign objects.

Rectifier A group of connected diodes (power diodes) for converting three-phase alternating current into direct current.

Regulator Adjusts the field voltage so that the alternator only produces the amount of current required by the components.

The rotor has an electromagnetic coil inside it. Both ends of the rotor are bent over the coil like claws. This creates Rotor a magnetic field with rapidly flipping north and south poles.

The shaft connects the belt pulley, fan, and rotor. High precision is required in order to ensure the durability of the Shaft roller bearings. However, this also allows the alternator to be designed with a small gap between the rotor and stator, significantly increasing its efficiency.

The two slip rings provide the solenoid coil inside the rotor with the excitation current. The regulator sends the excitation Slip ring current to the slip rings via carbon brushes.

The stator consists of three coils with an iron core. The rotor spins inside the stator. The changing magnetic fields generate Stator the three-phase current in the stator. 34 35

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