Charging System - General Information: Overview Mercury Milan I

Principles of Operation

The powertrain control module (PCM) controlled charging system determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator. This system is unique in that it has 2 unidirectional communication circuits between the PCM and the generator/regulator. Both of these communication circuits are pulse-width modulated (PWM). The generator communication (GEN COM) circuit communicates the desired setpoint from the PCM to the voltage regulator. The generator monitor (GEN MON) circuit communicates the generator load and error conditions to the PCM. The third circuit on the voltage regulator, the A circuit, is a dedicated battery voltage sense circuit.

The charging system voltage is controlled by the PCM. The generator charges the battery, and at the same time supplies voltage for all of the electrical loads that are required. The battery is more effectively charged with a higher voltage when the battery is cold and a lower voltage when the battery is warm. The PCM is able to adjust the charging voltage according to the battery temperature by using a signal from the intake air temperature (IAT) sensor. This means the voltage setpoint is calculated by the PCM and communicated to the regulator by the GEN COM circuit.

The PCM simultaneously controls and monitors the output of the generator. When the current consumption is high or the battery is discharged (the PCM recognizes this and increases the output of the generator to accommodate), the system is also able to increase the idle speed.

To minimize the engine drag when starting the engine, the PCM does not allow the generator to produce any output until the engine has started. The PCM then progressively increases the output of the generator.

The PCM is responsible for turning the charging system warning indicator off after the engine is started and illuminating it under fault conditions (when the generator is not generating the correct amount of current/voltage with the engine running). The charging system warning indicator is also illuminated by the PCM whenever the key is ON with the engine OFF.

This is a System 4 charging system, which uses the GEN MON and GEN COM circuits to control and monitor the charging system through the PCM. System 4 charging systems are virtually identical in design and therefore, share the same diagnostics. The circuit numbers and colors may be different, but the functions are the same. System 4 charging systems may use any type of generator, as the generator type usually depends on the engine packaging and/or output requirements versus cost.

Normal Operation

The generator output is supplied through the positive battery output (B+) terminal on the rear of the generator, circuit SDC14 (RD), to the battery and electrical system. During normal operation the charging system warning indicator is off with the key in the ON position and the engine running. The charging system warning indicator is on with the key in the ON position and the engine off.

Possible Causes

1. Engine, generator and battery grounds
2. Positive battery cable
3. Circuit SDC14 (RD) high resistance
4. High key-off current drain(s)
5. Battery
6. Generator

Scheme 4

Scheme 5

1. A1 CHECK THE BATTERY CONDITION Carry out the Battery - Condition Test to determine if the battery can hold a charge and is OK for use. Refer to «BATTERY, MOUNTING AND CABLES»(ref-271102) . Does the battery pass the condition test? YES : Go to A2 . NO : INSTALL a new battery. REFER to «BATTERY, MOUNTING AND CABLES»(ref-271102) . TEST the system for normal operation.
2. A2 CHECK THE GENERATOR OUTPUT Carry out the Generator On-Vehicle Load Test and No Load Test. Refer to «Component Tests»(ref-271108-S28212914332007110800000) . Does the generator pass the component tests? YES : Go to A3 . NO : INSTALL a new generator. REFER to «GENERATOR AND REGULATOR»(ref-271068) . TEST the system for normal operation.
3. A3 CHECK FOR CURRENT DRAINS Carry out the Battery - Drain Testing. Refer to «Component Tests»(ref-271108-S28212914332007110800000) . Are any circuits causing excessive current drains? YES : REPAIR as necessary. TEST the system for normal operation. NO : Go to A4 .
4. A4 CHECK THE VEHICLE GROUNDS Key in START position. With the engine running, measure the voltage drop between the generator housing and the battery ground terminal. Is the voltage drop less than 0.1 volt? YES : Go to A5 . NO : CHECK the engine ground, generator ground, and the battery ground for corrosion. TEST the system for normal operation.
5. A5 CHECK THE VOLTAGE DROP IN CIRCUIT SDC14 (RD) With the engine running, measure the voltage drop between the generator C102b, circuit SDC14 (RD) and the positive battery terminal. Is the voltage drop less than 0.1 volt? YES : DETERMINE if the customer left any component(s) on or if there is an intermittent excessive battery draw. TEST the system for normal operation. NO : CHECK for any corrosion in the circuit SDC14 (RD) and/or connections. REPAIR as necessary. TEST the system for normal operation.

With the engine running, the charging system warning indicator is off. The sense A circuit SBB18 (YE/RD)for 2.3L and 3.0L, SBB17 (RD) for 3.5L, to the generator field coil is 13-15 volts. The S (stator) circuit (internal to the generator) is used to feed back a voltage signal from the generator to the voltage regulator. This voltage is used by the powertrain control module (PCM) to turn off the charging system warning indicator. The positive battery output (B+), circuit SDC14 (RD), is the generator output supplied to the battery and electrical system.

Possible Causes

1. Circuit CDC10 (BU/OG) open or short to ground
2. Circuit CDC15 (VT) open or short to ground
3. Circuit SDC14 (RD) open or high resistance
4. Generator
5. PCM

The generator output is determined by the voltage of the A circuit SBB18 (YE/RD) for 2.3L and 3.0L, SBB17 (RD) for 3.5L. The A circuit voltage is compared to a set voltage internal to the regulator, and the regulator controls the generator field current to maintain the correct generator output. The set voltage varies with temperature and is typically higher in cold temperatures and lower in warm temperatures.

Possible Causes

1. Fuse
2. Circuit SBB18 (YE/RD) for 2.3L and 3.0L, open or high resistance
3. Circuit SBB17 (RD) for 3.5L, open or high resistance
4. Generator
5. Powertrain control module (PCM)

Scheme 6

1. C1 CHECK THE FAULT CODES IN THE PCM Connect the diagnostic tool. Key in ON position. Enter the following diagnostic mode on the diagnostic tool: Retrieve PCM DTCs Check for recorded PCM DTCs from the continuous and on-demand self-tests. Are any PCM DTCs recorded? YES : REFER to the «Introduction - Gasoline Engines»(ref-268480) . If referred here by the «Introduction - Gasoline Engines»(ref-268480) , go to C2 . NO : Go to C2 .
2. C2 CHECK THE BATTERY VOLTAGE Key in START position. With the engine running and all the accessories turned off, measure the voltage at the battery while varying the engine rpm. Is the voltage greater than 15.5 volts? YES : Go to C3 . NO : Go to C4 .
3. C3 CHECK FOR A VOLTAGE DROP IN THE BATTERY VOLTAGE SENSE CIRCUIT Key in OFF position. Disconnect: Generator C102a Measure the voltage between generator C102a-3, circuit 18 (YE/RD) for 2.3L and 3.0L, harness side and ground. Measure the voltage between generator C102a-3, circuit 17 (RD) for 3.5L, harness side and ground. Is the voltage within 0.5 volt of the battery voltage? YES : CONNECT the generator C102a. Go to C4 . NO : VERIFY the battery junction box (BJB) fuse 18 (10A) for 2.3L and 3.0L, fuse 17 (10A) for 3.5L is OK. If OK, REPAIR the circuit for high resistance. TEST the system for normal operation.
4. C4 CHECK THE GENERATOR PIDS Key in ON position. Enter the following diagnostic mode on the diagnostic tool: Monitor PCM PIDs Monitor the PID GEN_COM in the PCM. Does the GEN_COM PID read YES? YES : Go to C5 . NO : Go to C6 .
5. C5 CHECK THE GENERATOR INTEGRITY Key in OFF position. Disconnect: Generator C102a Key in ON position, engine OFF. Measure and record the battery voltage. Key in START position. NOTE: If the generator communication lines are disconnected (DTC P0626 may be set), the generator self-excites if it is operated at greater than 4,500 rpm (approximately wide open throttle [WOT]) for a minimum of 3 seconds. It then operates in a default mode at approximately 13.5 volts until the engine is turned off. With the engine running (after the brief WOT is carried out), measure the battery voltage. Does the battery voltage increase a minimum of 0.5 volt from the key ON, engine OFF measurement to the key ON, engine running measurement (after the brief WOT or snap acceleration is carried out)? YES : Go to C6 . NO : INSTALL a new generator. REFER to «GENERATOR AND REGULATOR»(ref-271068) . TEST for normal operation.
6. C6 CHECK FOR CORRECT PCM OPERATION Disconnect all of the PCM connectors. Check for: corrosion. pushed-out pins. Connect all of the PCM connectors and make sure they seat correctly. Operate the system and verify the concern is still present. Is the concern still present? YES : INSTALL a new PCM. REFER to «ELECTRONIC ENGINE CONTROLS - 2.3L»(ref-271070) (2.3L), «ELECTRONIC ENGINE CONTROLS - 3.0L (4V)»(ref-271071) (3.0L) or «ELECTRONIC ENGINE CONTROLS - 3.5L»(ref-271135) (3.5L). TEST the system for normal operation. NO : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

With the engine running, the charging system warning indicator is off. The sense A circuit SBB18 (YE/RD) for 2.3L and 3.0L, SBB17 (RD) for 3.5L, to the generator field coil is 13-15 volts. The S (stator) circuit (internal to the generator) is used to feed back a voltage signal from the generator to the voltage regulator. This voltage is monitored by the powertrain control module (PCM) to turn off the charging system warning indicator. The positive battery output B+, circuit SDC14 (RD), is the generator output supplied to the battery and electrical system.

Possible Causes

1. Generator
2. Instrument cluster (IC)
3. PCM

Under normal operation, the charging system warning indicator is on with the key ON and the engine off.

Possible Causes

1. Instrument cluster (IC)
2. Powertrain control module (PCM)

The generator is belt-driven by the engine accessory drive system.

Possible Causes

1. Loose bolts/brackets
2. Accessory drive belt
3. Generator/pulley

The generator radio suppression equipment reduces interference transmitted through the speakers by the vehicle electrical system.

Possible Causes

1. Generator
2. In-vehicle entertainment system