Classic cars forum & vehicle restoration.

[rcx822]

I'm fitting an alternator from a modern Vauxhall diesel car into a 1990's Vitara which I'm restoring. Both the original and new alternator have extra wires in addition to the chunky positive. What do these extra wires do? I think sometimes they are something to do with the alternator warning light. Is there any way to identify so I can connect the new alternator?

Original alternator had three wires plus the chunky positive. However the wiring diagram only shows two extra wires and shows that one goes direct to the drivers warning lights console (aka idiot lights). The other goes to the ignition coil, also the fuse box, drivers warning light console, heater blower switch, and other places beyond the fuse box.

New alternator has two wires plus the positive and I'm struggling to find a wiring diagram for the car it came from (1.7 CDI Astra).

[peter scott]

Hi Phil,

I don't know how much commonality there is with this modern stuff but looking at the Jaguar X type wiring diagrams the alternator connections are labeled as follows:

GR (the main output)
OG Field
RG Generator Control
U Charge / Fault
B ST4 (goes to the starter relay)

Peter

The engine control module (ECM) can switch the voltage regulator between two voltages to optimize the charging of the battery.The low voltage regulator setting is 13.6 volts and the high voltage regulator setting is 15.3 volts, measured with the generator at 25°C (77°F) and charging at a rate of 5 amps. These values decrease with a rise in temperature or current flow.The ECM determines the voltage setting of the voltage regulator. The high voltage setting is always selected by the ECM once the vehicle has started. The ECM determines the period of time that the high voltage setting is selected for.There are three different time periods selected by the ECM which is dependent upon the vehicle conditions when the vehicle is started:The longest time period is selected if the ECM determines that the vehicle has been 'soaking' for sufficient time to allow the engine coolant temperature (ECT) and the intake air temperature (IAT) to fall within 3°C (37°F) of each other.The intermediate time period is selected when the ECT and the IAT is below 5°C (41°F).The shortest time period is the default time and is used to provide a short period of boost charge.At the end of these time periods the voltage is always set to the low voltage setting to prevent the battery from being overcharged.The time periods are variable depending upon the temperature and the battery voltage. The target voltage of the battery varies between 14 volts and 15 volts depending upon the ambient temperature and the vehicle operating conditions. Once this target voltage has been achieved, providing the vehicle has been operating for at least the shortest time period, the ECM will reduce the voltage regulator to the minimum setting of 13.6 volts.There are three wires connected to the generator from the ECM by connector EN16:EN49-1; RG wire, is the voltage regulator request setting from the ECM to the generator.EN49-3; OG wire, is a pulse width modulated signal (PWM) from the generator to the ECM which enables the ECM to monitor the generator load on the engine.EN49-4; U wire, is the charge warning lamp signal wire from the generator to the ECM.If the voltage request signal wire (EN 49-1) is open circuit or short to battery positive, the generator will charge the battery at a setting of 15.3 volts. If the wire is short circuit to ground, the generator will charge the battery at a setting of 13.6 volts.A fault in the wiring or the connections from the generator to the ECM, will cause a fault code to be generated and stored in the ECM and the charge warning indicator lamp to be displayed in the instrument cluster (IC) after a short time.The charge warning indicator lamp is operated by the IC after receiving a signal from the ECM through the control area network (CAN).With the ignition switch in the RUN position the charge warning indicator lamp will be displayed in the IC when the generator is not generating power.If a fault is detected with the generator a fault code will be generated and stored by the ECM. The charge warning indicator lamp will also be displayed in the IC.

Vehicles With A 2.0L Diesel EngineThe diesel charging system differs from that used in petrol-engined variants in that it incorporates a 'smartcharge' function.This function is capable of supplying infinitely variable voltages to the battery, depending on the temperature and on the current requirements of the battery.The system continuously monitors the battery voltage and temperature (via the ambient air temperature sensor), and uses a map of both to deliver the optimum charge to the battery.Another feature of this system is that it uses a 'wake-up' and 'sleep' strategy, initiated by the ignition switch position and ECM, rather than being constantly active, to avoid current drain.
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1939 SS Jaguar 2 1/2 litre saloon