Alternator and Starter Diagnosis

Rotating electrical parts such as starters and alternators ofttimes have to be replaced on older, loftier-mileage vehicles. Fuel injection has helped prolong the service life of starters past assuasive engines to offset more quickly when they are cranked. Such is not the instance with alternators. Higher electrical demands on charging systems take increased alternator failures.

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Alternator and Starter

Starter Troubles
A starter that's failing may creepo the engine too slowly for a quick showtime, or it may not crank the engine at all. Oftentimes, the problem is not the starter but a low battery or a loose or corroded battery cable connection. And then, check the battery accuse and status first.

A good battery should be capable of accepting and holding a accuse from a battery charger, and should exist at to the lowest degree 75 percent charged (12.v volts or higher). If the battery's voltage is low and information technology doesn't have a charge, your customer needs a new bombardment. Load-testing the battery or using a conductance tester to check its ability to have and store a charge can also confirm the need for replacing the bombardment. The average service life of a machine bombardment is simply most four to five years, and can be shorter in hot climates. So also consider the age of the battery when evaluating its condition.

If a DIY customer is not sure what might exist causing his cranking problem, offering to bench-test his old starter. If the starter passes the tests, the slow-cranking or no-cranking problem is obviously something other than the starter. He should check the battery, bombardment cables, starter relay and the starter circuit and wiring connections for possible faults. If the starter fails the tests due to low cranking RPMs, excessive current draw or information technology failure to spin at all, you tin can sell your client a new or remanufactured starter with a high degree of confidence.

High resistance within the starter itself, worn brushes, or grounds or opens in the armature or coil windings can exist crusade excessive current draw. It can besides result from increased internal friction due to shaft bushings that bind or an armature or magnets that are rubbing inside the starter.

A loose starter may crank an engine slowly, noisily or non at all. Loose bolts will make for a weak basis connection. The starter may also flop around, slip, chatter or neglect to engage depending on how loose it is. Sometimes the engine won't crank even though the starter volition spin. This is usually an engagement problem due to a weak solenoid or a defective starter drive. A starter drive that is on the verge of failure may engage briefly but then sideslip. The starter drive has a one manner overrunning clutch mechanism that you tin can check once the starter is out of the motorcar (and replace if necessary). The drive should plough freely in 1 direction but not in the other if good. A bad drive volition turn freely in both directions or not at all. If a drive locks up, it tin can over-rev and destroy the starter.

Charging Problems
The beginning sign of trouble when an alternator is failing is a low or dead battery. On a late-model vehicle, that can not only cause a no-start simply also can cause the loss of "learned" data in the powertrain control module and other modules throughout the vehicle. In some cases, certain modules may non regain their normal part after the bombardment has been recharged because the module requires a special relearn procedure.

The output of the charging organization on a vehicle tin can be checked with a digital voltmeter while the engine is idling. A charging system that is working properly should produce a charging voltage of somewhere effectually 13.5 to 14 volts at idle with the lights and accessories off (always refer to the vehicle manufacturers specifications). When the engine is first started, the charging voltage should ascent quickly to well-nigh two volts above base battery voltage, and and so taper off, leveling out at the specified voltage.

The exact charging voltage will vary according to the battery'south state of charge, the load on the vehicle's electrical system, and temperature. The lower the temperature the higher the charging voltage, and vice versa.
If the charging output is depression, the alternator can be bench-tested to meet if it is good or bad. Make sure you lot utilise the correct wiring adapters for the unit of measurement and that all of the connections are made properly. The bench tester will bank check the alternator's voltage and current output, and also look for "ripple voltage" or alternate electric current leakage that would indicate bad diodes inside the alternator.

If the alternator fails the tests, your customer needs a new or remanufactured replacement alternator. You might use the opportunity to recommend a higher-output alternator if the customer's vehicle is equipped with a megawatt aftermarket sound organisation or other high-load electrical accessories.

If the alternator passes the tests, the problem is not the alternator only something in the wiring or the charging system control circuitry. High circuit resistance and basis connection resistance can cause depression charging output. Circuit resistance tin be checked by connecting a volt meter to the positive battery terminal and the positive last on the alternator. With the engine running and the headlights on, there should be less than one-half a volt voltage drop, and ideally less than one-tenth of a volt drop. A higher reading would indicate too much resistance. The same test can exist repeated using the bombardment negative terminal and the alternator housing to cheque for excessive resistance on the basis side of the circuit.

If the wiring checks out okay, the problem could be in the voltage regulating circuitry inside the powertrain control module. On many late-model vehicles, charging output can be varied depending on operating conditions equally well equally electrical load. Problems with other sensor inputs or a defect in the control module itself may prevent the alternator from charging properly.

A slipping drive belt is another common cause of undercharging, especially with Five-belts on older vehicles. Serpentine belts usually provide a ameliorate grip, merely if the automatic tensioner is weak or stuck it can permit the chugalug to slip nether load. Glazed streaks on the belt or chugalug noise when loftier-load electrical accessories are turned on with the engine idling can exist signs that the belt is slipping.

Alternator slippage and undercharging tin can also exist caused past a bad alternator pulley. Overrunning Alternator Pulleys (OAP) are used on a number of tardily-model import and domestic vehicles. OAP pulleys have a one-way clutch inside the middle of the pulley that slips and allows the pulley to gratis-bicycle when engine speed suddenly drops. This reduces noise, vibration and harshness in the chugalug drive system, but may crusade a charging problem if the clutch slips when it should be gripping.

Another type of pulley is the Overrunning Alternator Decoupler (OAD) caster. This type of pulley combines a 1-way clutch with a torsion spring to decouple and absorb torsional vibrations in the belt bulldoze system. This provides much quieter and smoother performance than either a solid caster or an OAP, particularly at lower engine speeds (from idle to about 1,500 RPM). Only it too tin can cause slipping and charging problems if the clutch or decoupler jump is defective.

Alternator Replacement
Some replacement alternators come up with a pulley already installed and some do not. If the replacement alternator comes with a pulley, make sure the pulley matches the original (aforementioned diameter, width and belt blazon). No caster means your customer will take to bandy the pulley from the sometime alternator to the replacement. Removing a conventional solid pulley usually requires a gear puller to pull the pulley off the alternator shaft. Simply on some applications, a threaded OAP or OAD pulley may be used and a special tool may be required to get it off.

OAP and OAD pulleys are more complicated and expensive than ordinary solid pulleys, only are installed on the alternator for a reason. Replacing an OAP or OAD caster with a less expensive solid pulley is possible, and some replacement alternators come up with a less expensive solid pulley installed rather than an overrunning clutch or decoupler pulley. Only replacing an OAP or OAD pulley with a solid pulley defeats the purpose of the original caster and may result in increased NVH, reduced belt and tensioner life and client complaints.

When a new or remanufactured alternator is installed on a high-mileage vehicle, recommend a new drive belt likewise. Original equipment belts made of EPDM synthetic prophylactic are high-mileage belts capable of lasting up of 100,000 miles. Different older belts made of less durable rubber, they don't cleft with age. But they do wear. It's difficult to see how much the grooves on the underside of the belt may be worn, so belt manufacturers accept created special belt wear tools that tin can check the depth of the grooves to reveal how much they are worn.

The operation of the automated belt tensioner also should exist checked to make sure it is working correctly and is capable of maintaining proper chugalug tension. Rust and corrosion can cause erstwhile tensioners to bind, and a weak or broken bound may foreclose it from keeping the belt tight.