Diagnostics and follow-up generator disassembly This is a critical step in maintaining your vehicle's electrical system. Often owners Nissan Qashqai encounter a characteristic howling sound from the engine compartment, which signals wear on the internal components. Ignoring such symptoms can lead to complete failure of an expensive unit and stopping the engine along the way.
The correct dismantling and inspection procedure allows you to identify hidden defects, such as jammed rotor or breakdown of diodes. Many car owners try to replace only the bearings, not realizing that the cause of the noise may be shaft deformation or damage to the slip rings.
β οΈ Attention: Before starting any work to remove the generator, be sure to disconnect the negative terminal of the battery. This will eliminate the risk of a short circuit in the on-board network and electric shock if metal tools accidentally touch the body.
## Preparing tools and dismantling the unit
The first step is to ensure easy access to the generator, which on most modifications Nissan Qashqai (especially with 1.5 dCi or 2.0 engines) is located at the bottom of the engine. You will need a standard set of ratchet wrenches, a 14mm and 17mm socket, and an extension for hard to reach areas.
First you need to loosen the tension on the alternator belt. To do this, use a special key for the tension roller, which must be turned counterclockwise. The loosened belt is removed from the generator pulley, after which you can unscrew the fastenings of the assembly itself.
- π οΈ Prepare a set of sockets from 8 to 17 mm and an extension
- π§ Buy a new belt if the old one has cracks or scuffs
- π¦ Use a powerful flashlight to inspect the mount from below
After removing the belt, unscrew the bolts securing the housing to the engine bracket. Be extremely careful when disconnecting power wires, as they often stick to the contact. Carefully unscrew the nut on the power terminal B+ and disconnect the chip with the signal wires.
β οΈ Attention: The power cable going to the battery is very thick and is often secured with a plastic bracket. Do not try to pull it by force, so as not to damage the terminal inside the generator housing.
- 1.5 dCi (K9K)
- 2.0 dCi (M9R)
- 1.6 (HR16)
- 2.0 (MR20)
## Removing the back cover and removing the brush assembly
After removing the generator from the car, you need to start disassembling it. You should start with the back cover, where the voltage regulator and diode bridge are located. Unscrew the three bolts securing the back cover using a screwdriver with an appropriate tip or an 8 mm socket.
Removing the brush assembly is a key diagnostic point. Voltage regulator automatically limits current excitation, and its failure is one of the most common causes of unstable charging. Unscrew the two screws holding the brush holder in place and carefully remove the assembly.
- β Inspect the length of the graphite brushes - the minimum acceptable length is 5 mm
- π Check the springs for loss of elasticity or corrosion
- π§Ή Clean the rotor contact rings from carbon deposits with fine sandpaper
It is important to inspect the rotor slip rings for deep grooves or burning. If the surface of the rings is severely worn, replacing the brushes will not solve the problem and a more extensive repair or replacement of the armature will be required.
Why do brushes wear out quickly?
Rapid wear of the brushes can be caused not only by their poor quality, but also by contamination of the bearings, which is why the rotor begins to play and hit the brushes. Also the cause may be surge voltage in the network.
## Removing the front cover and dismantling the rotor
To access the front cover bearings, you need to unscrew the four bolts connecting the stator to the front and rear parts. This requires significant force, since the bolts are often tightened at the factory with a high torque.
After disconnecting the housing, the rotor (armature) is removed. Be careful: the rotor bearing is often very tight and can damage the slip rings if knocked out roughly. Use a puller or carefully tap through the wooden spacer, striking the end of the shaft, not the copper windings.
β οΈ Attention: Do not hit the rotor shaft directly with a hammer in the area of the slip rings - this will instantly lead to their deformation and the impossibility of further use of the generator.
- π¨ Use a soft spacer (wood, brass) to knock out the rotor
- π οΈ Use a puller to remove the pulley if it is stuck
- π§ Check the key on the pulley for damage
βοΈ Tools for disassembling the front cover
Before unscrewing the bolts connecting the covers, make marks with a marker at the junction of the body. This will help during assembly to align the stator and covers exactly as they were at the factory, which will reduce vibrations.
## Diagnostics of diode bridge and stator
The diode bridge (rectifier unit) is responsible for converting alternating current to direct current. Checking it requires a multimeter. It is necessary to check each diode for breakdown and open circuit. If one of the diodes is broken, it will create a constant current leakage, which will lead to rapid discharge of the battery even with the engine off.
The generator stator is checked for interturn short circuits and winding integrity. Visually you can see blackening of the insulation or signs of overheating. However, accurate diagnosis is carried out only with an ohmmeter, measuring the resistance between the phases.
| element | Symptom of malfunction | Check result | Recommended Action |
|---|---|---|---|
| Diode bridge | Breakdown or break | Multimeter shows 0 ohm or infinity | Replacing the rectifier unit |
| Rotor (winding) | Short to ground | Resistance between slip ring and shaft less than 1 MΞ© | Rewinding or replacing the rotor |
| Stator | Interturn closure | Resistance inequality between phases | Replacing the stator assembly |
| Bearings | Noise, backlash | Visual play, lack of lubrication | Replacing bearings |
Pay special attention to the condition of the wire insulation. On Nissan Qashqai Damage to the braid due to friction against the motor housing or belt is common.
The diode bridge often fails due to voltage surges caused by a faulty voltage regulator or poor contact at the battery terminals.
## Replacing bearings and assembling the unit
Replacing bearings requires care and the right tools. Bearings are often pressed into the cap housing. To remove them, use a mandrel that rests on the inner race of the bearing. Knocking through the outer ring will destroy the cage and bearing.
When installing new bearings, make sure they are fully seated. Before pressing, apply a small amount of high temperature grease to the inside of the bearing. This will extend its service life and reduce the noise level during operation.
- π§ Use a mandrel of the appropriate diameter for pressing
- π’οΈ Use only specialized lubricant for electric motors
- π© Observe the tightening torque of the cover bolts according to the specifications
The generator is reassembled in the reverse order. It is important not to overtighten the bolts, since the aluminum housing of the covers is easily deformed, which will lead to the rotor being skewed and jamming.
How to check the quality of bearing pressing?
After installing the bearing in the cover, try turning it with your fingers. It should rotate smoothly, without jamming or extraneous sounds. Play relative to the seat is unacceptable.
## Final check and installation on the car
Before installing the generator on the engine, you must make sure that all connectors are connected securely and the power wire is clamped with the correct tightening torque. Check the condition of the pulley: it should rotate freely, but without axial play.
After installing the unit in place, put on the belt and adjust its tension. On modern models Nissan Qashqai An automatic tensioner is used, which does not require manual adjustment, but requires checking the condition of the spring and roller.
β οΈ Attention: After starting the engine, be sure to check the voltage at the battery terminals. It should be from 13.8 to 14.5 volts on a warm engine with consumers turned on.
If the voltage goes beyond these limits, it means that errors were made during assembly, or the voltage regulator is faulty. Do not continue to operate a vehicle with a faulty charging system as this may damage the electronics.
Proper tightening of the power terminal and checking the belt tension are two factors that guarantee stable operation of the generator without overheating the contacts.
## FAQ: Frequently asked questions
How long does it take to completely disassemble a generator?
If you have the necessary tools and experience, the disassembly and assembly process takes from 1.5 to 3 hours. If bearing replacement and winding diagnostics are required, the time may increase to 4-5 hours.
Is it possible to replace just the bearings without removing the generator?
No, replacing the bearings requires complete disassembly of the unit, since they are located inside the housing. Access to them is possible only after removing the covers and removing the rotor.
What tools are needed to remove the pulley?
To remove a pulley, a special puller is often required, since it is mounted on the shaft with great tension. Sometimes a two- or three-jaw puller is used, resting on the pulley and the central bolt.
Why might a new generator hum?
The hum of a new generator can be caused by misalignment during installation, improper tightening of fasteners, or defective bearings. It could also be due to a belt that is too stiff or a worn tension roller.