I have a 91 ram d250 318 carb. my battery is new, alternater and voltage test out fine. Still wont hold a charge, Ive read that if all that checks out maybe the pcm is bad? anyone have this prob?
thanks alot
Ted

 

Voltage regulator is in the PCM and they are a problem area. You should check the codes in your PCM and see if you have a 41

 

2 weeks later back to same issue, sucks ***** here lol

 

I see you have a Code 47 and a Code 41 now. the Code 47 will usually precede the Code 41.

Code 41 Alternator field circuit
An open or shorted condition detected in the alternator field control circuit.
Code 47 Battery voltage low
Battery voltage sense input below target charging voltage during engine operation.

Ok, you have a new battery so lets rule that out for now.

1. Did you replace the battery cable assembly/s? Do not use emergency battery cable clamps at the battery.

2. Having the alternator checked just shows it's good "at that time"...there can be internal shorts, worn brushes,etc that wont show up until your engine is hot/cold or the truck hits a bump,etc.

3. You're gonna have to get into the wiring and check some things out or take the truck to an auto electric shop.
Do you want some further diagnostics for the wiring?


Description and Operation
Voltage regulation is necessary on all vehicles that have a charging system with an alternator. All voltage regulators limit the voltage the vehicle's charging system produces. The need for this regulation is most critical on vehicles with electronic devices, such as an engine controller, body controller, or ETR radio. Inconsistent voltage levels or excessively high or low voltage levels have a negative effect on the performance and durability of electronic components.
There are two basic functions of a voltage regulator:

To maintain a constant system voltage regardless of the vehicle's electrical load requirements or its engine speed.
To regulate system voltage to keep the battery at an optimum state of charge.
The engine controller contains the voltage regulator function. The engine controller uses the battery voltage sense, the battery temperature sensor, and its own program to determine the charging system's voltage goal. The voltage goal is adjusted by the controller based on changes in the voltage sense and temperature values.
The basic voltage regulating function is to keep the charging system voltage between 12.9 and 15.0 volts. The voltage regulator accomplishes this by controlling the current flow through the rotor. Since the rotor is electromagnetic, controlling the current through the rotor effectively limits the strength of the magnetic field and the output of the alternator.
BATTERY VOLTAGE SENSE
The battery voltage sense is the sensor value that establishes the basic charging rate of the alternator. The voltage level sensed is used by the engine controller to determine the vehicle's electrical load condition and the battery's state of charge.
The engine controller controls the alternator's field ground based on how close the battery sense voltage is to the voltage goal. If the battery sense voltage is below the voltage goal, the engine controller initiates the grounding of the field. If the battery sense voltage is above the voltage goal, the module stops grounding the field, thus effectively disabling the magnet and stopping output.
BATTERY TEMPERATURE SENSOR
The battery temperature sensor signal is a voltage used by the engine controller to report the temperature under the hood. This temperature is used to indicate the battery temperature. The battery's temperature is critical to its state of charge and to determining the charging rate.

sensor, and its own program to determine the charging system's voltage goal. The voltage goal is adjusted by the controller based on changes in the voltage sense and temperature values.
The basic voltage regulating function is to keep the charging system voltage between 12.9 and 15.0 volts. The voltage regulator accomplishes this by controlling the current flow through the rotor. Since the rotor is electromagnetic, controlling the current through the rotor effectively limits the strength of the magnetic field and the output of the alternator.
BATTERY VOLTAGE SENSE
The battery voltage sense is the sensor value that establishes the basic charging rate of the alternator. The voltage level sensed is used by the engine controller to determine the vehicle's electrical load condition and the battery's state of charge.
The engine controller controls the alternator's field ground based on how close the battery sense voltage is to the voltage goal. If the battery sense voltage is below the voltage goal, the engine controller initiates the grounding of the field. If the battery sense voltage is above the voltage goal, the module stops grounding the field, thus effectively disabling the magnet and stopping output.
BATTERY TEMPERATURE SENSOR
The battery temperature sensor signal is a voltage used by the engine controller to report the temperature under the hood. This temperature is used to indicate the battery temperature. The battery's temperature is critical to its state of charge and to determining the charging rate.