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Jerry, Master Mechanic
Category: Chrysler
Satisfied Customers: 16826
Experience:  ASE Master tech. 30+ years mechanic, shop forman, service manager
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Battery light come on after replacing the alternator with a new one?

Customer Question

Why does my battery light come on after replacing the alternator with a new one?
Submitted: 7 years ago.
Category: Chrysler
Expert:  Jerry replied 7 years ago.

Hello and welcome to Just, Super mechanic here. About your vehicle.


What is the year make and model of it?


Customer: replied 7 years ago.
2006 chrysler sebring touring convertible 2.7 v6
Expert:  Jerry replied 7 years ago.

You will want to be sure that there is power at the alternator at all times, (big red wire)


Unfortunatly the voltage regulator is built into the PCM, (powertrain control module) and if the fuse links are good, (power at the alternator) then the PCM would be the most likely problem. Or the alternator could be bad. You will want to test the charging system.







Of course, you will want to make sure that the alternator is grounded well also.


Description and Operation

The Electronic Voltage Regulator (EVR) is not a separate component. It is actually a voltage regulating circuit located within the Powertrain Control Module (PCM). The EVR is not serviced separately. If replacement is necessary, the PCM must be replaced.

The amount of DC current produced by the generator is controlled by EVR circuitry contained within the PCM. This circuitry is connected in series with the generators second rotor field terminal and its ground.


Customer: replied 7 years ago.
The alternator is brand new (chrysler manufactured....) They ran diagnostics and said that the alternator wasn't putting out enough juice and that it needed to be factory..... so they switched it out.......
Expert:  Jerry replied 7 years ago.

Was the battery light on before the alternator was replaced?


Do you know that it is charging?

Customer: replied 7 years ago.
The battery light was on before the alternator was changed. The car shop that was working on it put a rebuilt alt. in, but it didn't fix the problem so they sent it to the dealership to get it diagnosed, that is when the dealership said that it needed a factory alt. for it to get enough amps.... so the car place replaced the alternator with a factory one.... the light went off for a few minutes to half an hour, then came back on..... I have know personal idea whether it is charging correctly or not... it seems that I am missing some interior lighting, but the car starts up and runs fine.... thought about replacing the battery and checking the battery connections.... other than that I am at a lost with the exception of the computer nodes that communicate between the parts and the boards.... I will check back in the morning for a reply.
Expert:  Jerry replied 7 years ago.

It sounds like someone is not diagnosing it correctly. Or there is a problem with the PCM.




Testing and Inspection

The Powertrain Control Module (PCM) monitors critical input and output circuits of the charging system, making sure they are operational. A Diagnostic Trouble Code (DTC) is assigned to each input and output circuit monitored by the OBD system. Some circuits are checked continuously and some are checked only under certain conditions.

If the OBD system senses that a monitored circuit is bad, it will put a DTC into electronic memory. The DTC will stay in electronic memory as long as the circuit continues to be bad. The PCM is programmed to clear the memory after 40 good trip if the problem does not occur again.

A DTC description can be read using the DRBIII(R) scan tool.

A DTC does not identify which component in a circuit is bad. Thus, a DTC should be treated as a symptom, not as the cause for the problem. In some cases, because of the design of the diagnostic test procedure, a DTC can be the reason for another DTC to be set. Therefore, it is important that the test procedures be followed in sequence, to understand what caused a DTC to be set.

The DRBIII(R) Scan Tool must be used to erase a DTC.

The following procedures may be used to diagnose the charging system if:

  • the check gauges lamp or battery lamp is illuminated with the engine running
  • the voltmeter (if equipped) does not register properly
  • an undercharged or overcharged battery condition occurs.

Remember that an undercharged battery is often caused by:

  • accessories being left on with the engine not running
  • a faulty or improperly adjusted switch that allows a lamp to stay on.
  • loose generation belt.

The Powertrain Control Module (PCM) monitors critical input and output circuits of the charging system, making sure they are operational. A Diagnostic Trouble Code (DTC) is assigned to each input and output circuit monitored by the On-Board Diagnostic (OBD) system. Some charging system circuits are checked continuously, and some are checked only under certain conditions.

This will include a complete list of DTC's including DTC's for the charging system.

To perform a complete test of the charging system, refer to the appropriate Powertrain Diagnostic Procedures the DRBIII(R) scan tool. Perform the following inspections before attaching the scan tool.

  1. Inspect the battery condition.
  2. Inspect condition of battery cable terminals, battery posts, connections at engine block, starter solenoid and relay. They should be clean and tight. Repair as required.
  3. Inspect all fuses in both the fuse block and Power Distribution Center (PDC) or IPM (if equipped) for tightness in receptacles. They should be properly installed and tight. Repair or replace as required.
  4. Inspect generator mounting bolts for tightness. Replace or tighten bolts if required. Refer to the Generator Removal/Installation section for torque specifications.
  5. Inspect generator drive belt condition and tension. Tighten or replace belt as required. Refer to Belt Tension Specifications.
  6. Inspect decoupler pulley (if equipped). Ensure decoupler pulley is driving the alternator rotor.
  7. Inspect automatic belt tensioner (if equipped). Refer to the Cooling System for more information.
  8. Inspect generator electrical connections at generator field, battery output, and ground terminal (if equipped). Also check generator ground wire connection at engine (if equipped). They should all be clean and tight. Repair as required.

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