1998 JAGUAR X308 belt tensioner

Belt tension is achieved by an automatic tensioner; neither the belt nor the tensioner require service apart from checking
the belt wear indicators at each normal service interval.
The minimum service life of the drive belt is 100,000 miles.
Never apply oil to the belt or to the belt tensioner.
Generator - Charging Circuit

Parts List
The main components of the charging system are shown above.
The output from the generator 'B+' main te rminal passes to the battery via the main terminal on the starter motor and then
the power cable to the high power protection module located in the luggage compartment. From this module, a short main
power cable supplies the ba ttery positive terminal.
The return circuit is through the vehicle body and supplementary ground cables.
The high power protection mo dule comprises four fuses, each rated at 250 Amps.
Battery output uses the same power cable as the charging circ uit, to the high power protection module and to the starter
motor main terminal. Two similar cables, but not such a high rating, supply battery power from the high power protection
module to the fuse box in the luggage compartment an d to the fuse boxes at the front of the vehicle.
ItemPart NumberDescription
1—Generator
2—Suppression Module
3—Starter Motor
4—Battery
5—Power Cable to Rear Fuse Box
6—High Power Protection Module
7—Power Cable to Front Fuse Boxes

If the field were not controlled, the 'B+' output would rise to a level which could damage bulbs and ECMs. The regulator
compares the output voltage to an intern al voltage reference circuit to achieve the controlled output of the generator.
Suppression Module

Although the output from the generator is fi nely controlled and relatively smooth, it is still a pulsed DC output at a varying
frequency proportional to engine speed.
The suppression module damps ou t any ripple which may be sensed on the main output of the generator. This prevents
possible interference via the power supply, affecting the radio reception or, where fitted, the telephone.
The module is located on the right hand side of the engine compartment, on the inner panel just above the chassis leg,
adjacent to the generator. It is secured to two anti-vibration rubber moun tings. The illustration shows the suppression
module viewed from below the vehicle.
A fuse is fitted internally to the suppression module to protect the generator output in the event of a short circuit within th e
suppression module.
Drive Belt Automatic Tensioner

Belt tension is achieved by an automatic tensioner; neither the belt nor the tensioner require service apart from checking
the belt wear indicators at each normal service interval.
The minimum service life of the drive belt is 100,000 miles.
Never apply oil to the belt or to the belt tensioner.


ItemDescription
1New Belt - Minimum Length
2New Belt - Maximum Length
3Replace the Belt

Generator and Regulator - Generator
Diagnosis and Testing
Refer to PDU User Guide
Refer to the PDU User Manual for detailed instructions on testing the charging circuit.
When diagnosing the charging ci rcuit, the PDU indicates only whether the generator is charging or not charging. The reason
for this is that the PDU cannot handle the potential full charging current and that the voltage control circuits are located
within the generator assembly, making th em inaccessible by the PDU directly.
It is possible that the battery has failed. In this case, the voltage output at the generator could be correct, but the voltage
at the battery terminals, and therefore the rest of the vehicl e system, will be adversely affected by the faulty battery.
The same result is given by the PDU if the battery is faulty (generator not faulty), wiring fault (damaged or severe corrosion
at the terminals) or if th e generator is at fault.
Inspection and Verification
The following manual tests help to pinpoint which component is at fault.
Testing the Battery Circuit
Using the Vehicle Battery

Remove the battery cover.
Ensure that all electrical loads are swit ched OFF and that the engine is cool.
Start the engine and allow to IDLE.
Whilst the engine is idling, disconnect the battery negative terminal and, using a digital multimeter (DMM), measure the
voltage between the terminal on the batter y negative cable and the battery positive terminal. If the generator is working,
the measured voltage should be within the range 13V to 15V.
This indicates the system voltage without the battery in circuit. If the generator is inoperative, the engine will stall when t he
ground lead is disconnected.
Repeat the test, using the ground bolt, as indicated (shown dotted on the illustration). There should be hardly any
MechanicalElectrical
Visually check the condition of the drive beltConnections on the rear face of the generator
are fully located?
Check that the belt we ar indicator, located on the automatic belt
tensioner, is within the limit marks

Generator and Regulator - Generator4.0L NA V8 - AJ27/3.2L NA V8 - AJ26
Removal and Installation
Removal

1. Disconnect the batt ery ground cable.
Remove the battery cover.
2. Remove the air cleaner assembly (including fit body paintwork
protection sheets to the adja cent working area); refer to
operation 19.10.05.
3. Remove the twin fan and moto r assembly from behind the
radiator; refer to operation 26.25.12.
4. Check that the belt wear indicator is within the limit marks.

5. Remove the drive belt from the generator and accessory
drive,
1. Use a spanner e.g. Churchill JD-230 or Snap On XDHM 1415, on the centre bo lt of the belt tensioner
idler pulley, to turn the adju ster assembly to the left
against spring tension.
2. Whilst holding the tensioner against spring tension, remove the drive belt from the generator pulley.
Release the tensioner sl owly and remove the
spanner.
Disconnect the belt from the ot her pulleys, as necessary,
to move it clear of the generator.
6. Raise the vehicle on a ramp; refer to Section 100-02

7. Remove the air intake ducting fr om the generator. The ducting
comprises two sections; the upper section is retained by two
screws to the sump body assembly and the lower (horizontal)
section is retained by one screw.
8. Disconnect the generator harness.
1. Disconnect the harness multi-plug.
2. Remove the protective boot from the positive
terminal, remove the termin al nut and disconnect the
cable from the terminal. Where fitted, disconnect the

2. Secure the suppression module positive cable and
main positive cable to the generator positive
terminal.
3. Fit the boot to the terminal.
4. Reconnect the generator harness multi-plug.

4. Refit the air intake ducting to the generator. The upper section
is retained by two screws to the sump body assembly and the
lower (horizontal) section is retained by one screw.
5. Lower the vehicle on the ramp ; refer to Section 100-02.
6. Fully tighten the generator upper mounting bolt, to 18-24 Nm.

7. Refit the drive belt to the generator.
1. Pass the drive belt around the idler pulley.
2. Using spanner )Churchill JD-230 or Snap On XDHM 1415) on the centre bolt of the belt tensioner idler
pulley, rotate the adjuster against spring tension.
3. Whilst holding the tensioner against spring tension, pass the drive belt over the generator pulley and
check that it is correctly located on the other pulleys.
Release the tensioner slowly and remove the
spanner. Check the alignment of the belt.
8. Refit the fan and motor assembly ; refer to Operation 26.25.12.

9. Refit the air cleaner assembly; refer to Operation 19.10.05.
10. Reconnect the battery ground cable and fit the battery cover.
Reset the radio inform ation and the clock.

Generator and Regulator - Generator4.0L SC V8 - AJ26
Removal and Installation
Removal

1. Disconnect the batt ery ground cable.
Remove the battery cover.
2. Remove the air cleaner assembly (including fit body paintwork
protection sheets to the adja cent working area); refer to
operation 19.10.05.
3. Remove the twin fan and moto r assembly from behind the
radiator; refer to operation 26.25.12.
4. Remove the supercharger drive belt; refer to operation
18.50.08.
5. Remove the supercharger driv e belt tensioner; refer to
operation 18.50.24.
6. Check that the belt wear indica tor (accessory drive) is within
the limit marks.

7. Remove the drive belt from the generator and accessory
drive,
1. Use a spanner e.g. Churchill JD-230 or Snap On XDHM 1415, on the centre bo lt of the belt tensioner
idler pulley, to turn the adju ster assembly to the left
against spring tension.
2. Whilst holding the tensioner against spring tension, remove the drive belt from the generator pulley.
Release the tensioner sl owly and remove the
spanner.
Disconnect the belt from the ot her pulleys, as necessary,
to move it clear of the generator.
8. Raise the vehicle on a ramp; refer to Section 100-02

9. Remove the air intake ducting fr om the generator. The ducting
comprises two sections; the upper section is retained by two
screws to the sump body assembly and the lower (horizontal)
section is retained by one screw.
10. Disconnect the generator harness.

1415) on the centre bolt of the belt tensioner idler
pulley, rotate the adjuster against spring tension.
3. Whilst holding the tensioner against spring tension, pass the drive belt over the generator pulley and
check that it is correctly located on the other pulleys.
Release the tensioner slowly and remove the
spanner. Check the alignment of the belt.
9. Fit the supercharger drive belt tensioner; refer to operation
18.50.24.
10. Fit the supercharger drive belt ; refer to operation 18.50.08.
11. Refit the fan and motor asse mbly; refer to Operation
26.25.12.
12. Refit the air cleaner assembly; refer to Operation 19.10.05.
13. Reconnect the battery ground cable and fit the battery cover.
Reset the radio inform ation and the clock.