Charging System - General Information: Other Mercury Montego III

Battery

The battery is a 12-volt DC source connected in a negative ground system. The battery case is sealed and includes 2 vent holes to release gases. The battery has 3 major functions

1. engine cranking power source
2. voltage stabilizer for the electrical system
3. temporary power when electrical loads exceed the generator output current

Refer to SYSTEM WIRING DIAGRAMS (Montego), SYSTEM WIRING DIAGRAMS (Five Hundred), or SYSTEM WIRING DIAGRAMS (Freestyle) , Charging System for schematic and connector information.

Positive Battery Output (B+) Terminal Circuit 38 (BK/OG)

The generator output voltage is supplied through the positive battery output (B+) terminal circuit 38 (BK/OG) on the rear of the generator to the battery and electrical system.

A Circuit 1818 (WH/BK)

This is the A terminal battery voltage sense circuit and is used to sense battery voltage.

Circuit 1817 (YE)

The GEN MON circuit communicates the generator load and error conditions to the PCM.

I Circuit 1816 (YE/LB)

This is the GEN COM circuit. The PCM determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator via the GEN COM circuit.

Possible Causes

1. generator B+ circuit 38 (BK/OG) high resistance
2. engine, generator and battery grounds
3. positive battery cable
4. high key-off current drain(s)
5. battery
6. generator

Note. While carrying out pinpoint tests, disregard any DTCs that are set. After the completion of any test, be sure to clear all DTCs.

Note. All voltage measurements are referenced to the negative (-) battery post unless otherwise specified.

Scheme 10

Scheme 11

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-233036) . Does the battery pass the condition test? Yes : GO to A2. No : INSTALL a new battery. REFER to «BATTERY, MOUNTING AND CABLES»(ref-233036) . 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-233025-S21478950362006052400000) . Does the generator pass the component tests? Yes : GO to A3. No : INSTALL a new generator. REFER to «GENERATOR AND REGULATOR»(ref-233004) . TEST the system for normal operation.
3. A3 CHECK FOR CURRENT DRAINS Carry out the Battery - Drain Test. Refer to the «COMPONENT TESTS»(ref-233025-S21478950362006052400000) . Are any excessive current drains present? 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 negative battery 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 THE B+ CIRCUIT With the engine running, measure the voltage drop between the generator B+ C102b, circuit 38 (BK/OG) and the positive battery terminal. Is the voltage drop less than 0.1 volt? Yes : VERIFY 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 positive battery cable and/or connections. REPAIR as necessary. TEST the system for normal operation.

1. generator B+ circuit 38 (BK/OG) open or high resistance
2. GEN COM circuit 1816 (YE/LB) open or shorted to ground
3. GEN MON circuit 1817 (YE) open or shorted to ground
4. generator
5. PCM

Scheme 12

Scheme 13

Scheme 14

Scheme 15

1. B1 CHECK THE DTCs IN THE PCM Check the recorded PCM DTCs from the continuous and on-demand self-tests. Are any PCM DTCs recorded? Yes : REFER to the «INTRODUCTION - GASOLINE»(ref-229953) article . No : GO to B2.
2. B2 CHECK THE GENERATOR B+ CIRCUIT FOR VOLTAGE Key in OFF position. Measure the voltage between the generator C102b, circuit 38 (BK/OG) and ground. If Is the voltage equal to positive battery voltage? Yes : GO to B3. No : REPAIR the circuit. TEST the system for normal operation.
3. B3 CHECK THE GENERATOR INTEGRITY Disconnect: Generator C102a. Key in START position. NOTE: If the generator communication lines are disconnected, DTC P0622 may set, and the generator self-excites if it is operated at approximately 2,000 engine rpm for a momentary period of time. It then operates in a default mode at 13.5 volts until the engine is turned off. With the engine running at approximately 2,000 rpm, measure the battery voltage. Is the battery voltage approximately 13.5 volts? Yes : GO to B4. No : INSTALL a new generator. REFER to «GENERATOR AND REGULATOR»(ref-233004) . TEST the system for normal operation.
4. B4 CHECK CIRCUIT 1816 (YE/LB) FOR AN OPEN OR SHORT TO GROUND Key in OFF position. Disconnect: PCM C175e. Measure the resistance between the generator C102a-2, circuit 1816 (YE/LB), harness side and the PCM C175e-13, circuit 1816 (YE/LB), harness side; and between the generator C102a-2, circuit 1816 (YE/LB), harness side and ground. Is the resistance less than 5 ohms between the generator and the PCM, and greater than 10,000 ohms between the generator and ground? Yes : GO to B5. No : REPAIR the circuit. TEST the system for normal operation.
5. B5 CHECK CIRCUIT 1817 (YE) FOR AN OPEN OR SHORT TO GROUND Measure the resistance between the generator C102a-1, circuit 1817 (YE), harness side and the PCM C175e-26, circuit 1817 (YE), harness side; and between the generator C102a-1, circuit 1817 (YE), harness side and ground Is the resistance less than 5 ohms between the generator and the PCM, and greater than 10,000 ohms between the generator and ground? Yes : GO to B6. No : REPAIR the circuit. TEST the system for normal operation.
6. B6 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»(ref-233038) . REPEAT the self-test. 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.

1. A circuit 1818 (WH/BK) high resistance
2. generator
3. PCM

Scheme 16

1. C1 CHECK THE DTCs IN THE PCM Check the recorded PCM DTCs from the continuous and on-demand self-tests. Are any PCM DTCs recorded? Yes : REFER to the «INTRODUCTION - GASOLINE»(ref-229953) article . 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 THE VOLTAGE IN CIRCUIT 1818 (WH/BK) Key in OFF position. Disconnect: Generator C102a. Measure the voltage between the generator C102a-3, circuit 1818 (WH/BK), harness side and ground. Is the voltage within 0.5 volt of battery voltage? Yes : CONNECT the generator C102a. GO to C4. No : REPAIR the circuit for high resistance. TEST the system for normal operation.
4. C4 CHECK THE GENERATOR PIDs Connect the diagnostic tool. Key in START position. Enter the following diagnostic mode on the diagnostic tool: Monitor PCM PIDs. With the engine running, monitor the generator output fault PID in the PCM. Does the 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 START position. NOTE: If the generator communication lines are disconnected, DTC P0622 may be set, and the generator self-excites if it is operated at approximately 2,000 engine rpm for a momentary period of time. It then operates in a default mode at 13.5 volts until the engine is turned off. With the engine running at approximately 2,000 rpm, measure the battery Is the battery voltage approximately 13.5 volts? Yes : GO to C6. No : INSTALL a new generator. REFER to «GENERATOR AND REGULATOR»(ref-233004) . TEST the system 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»(ref-233038) . REPEAT the self-test. 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.

1. generator
2. instrument cluster
3. PCM

1. instrument cluster
2. PCM

1. loose bolts/brackets
2. accessory drive belt
3. generator/pulley

1. generator
2. in-vehicle entertainment system

Generator On-Vehicle Tests

Note. Battery posts and cable clamps must be clean and tight for accurate meter indications.

Note. Refer to the tester manual for complete directions for testing the charging system.

1. Turn off all lamps and electrical components.
2. Place the transmission in NEUTRAL and apply the parking brake.
3. Carry out the following generator tests

Scheme 17

1. Switch the tester to the ammeter function.
2. Connect the positive and negative leads of the tester to the corresponding battery terminals.
3. Connect the current probe to the generator B+ output terminal, circuit 38 (BK/OG).
4. With the engine running at approximately 2,000 rpm, adjust the tester load bank to determine the output of the generator. The generator output should be greater than the graph shown below. If not, refer to the pinpoint test or GO to «SYMPTOM CHART»(ref-233025-S01981362172006052400000) .