Mightymouse is right, it's a traditional type of alternator with the voltage regulation done by the TIPM. The TIPM has some sort of feedback from the battery, presumably temperature. I have potentiometers on my dash and voltage seems to be highest on a hot day, but there is not really any logical trend that I've noticed to be honest. Voltage seems to bounce between 14.5 and 15.3 (2009 CRD) most of the time at the higher end (that's what kills batteries).

The system is perfectly suitable for a VSR dual bat system if that's what you're getting at.

That might be a 3.6 thing..... my 3.8 doesn't have a battery temp sensor ( that I can see or find on the schematic ) and doesn't drop voltage as things warm up.

Pity... its a good idea.

No battery temp sensor on CDR. There is one inside the TIPM (I call it ECU). But Chrysler software is dodgy and commands the alternator (via LIN bus) to go over 15.0V on hot days (noted 15.8V on mine). That's exactly what shortens the life of D31A to ridicules max 3 years. When I unplugged it from the ECU, it went to default 14.3 that's exactly midpoint of D31A charging range 13.6 to 15.0.

The alternator is not on LIN.....

Here's the description of the systems operation straight from the manual.

"Voltage is regulated by cycling the ground path to control the strength of the rotor magnetic field. The EVR circuitry monitors system line voltage (B+) and battery temperature (refer to Battery Temperature Sensor for more information). It then determines a target charging voltage. If sensed battery voltage is 0.5 volts or lower than the target voltage, the PCM grounds the field winding until sensed battery voltage is 0.5 volts above target voltage. A circuit in the PCM cycles the ground side of the generator field up to 100 times per second (100Hz), but has the capability to ground the field control wire 100% of the time (full field) to achieve the target voltage. If the charging rate cannot be monitored (limp-in), a duty cycle of 25% is used by the PCM in order to have some generator output."

You described the old school system with field excite control by internal regulator. On newer systems the internal regulator can be adjusted by the car ECU.

This is what I read in my service manual for CRD, and and this is exactly what's on my JK (diesel):

1 - PCM
2 - TIPM
3 - Battery
4 - Generator
5 - Feed Back Circuit B+
6 - Control Circuit
7 - Battery Sense

On gasoline powered engines, the charging system is turned on and off with the PCM (Powertrain Control Module) and ignition switch with engine running. On diesel powered engines, the charging system is turned on and off with the ECM (Engine Control Module) and ignition switch with engine running. The field circuit will not be energized until engine is running and ignition switch on. This voltage is connected through the PCM and supplied to one of the generator field terminals (Gen. Source B+) at the back of the generator. The generator is internally grounded. The generator regulates the field using pin-1 of the field connector (high side driver).

The generator is driven by the engine through a serpentine belt and pulley, or a decoupler pulley arrangement.

The PCM, or ECM receives a voltage input from the generator (5) and also a battery voltage input (7) from the TIPM (Totally Integrated Power Module), it then compares the voltages to the desired voltage programed in the EVR (Electronic Voltage Regulator) software, and, if there is a difference it sends a signal to the generator EVR circuit to increase or decrease output. It uses a Pulse Width Modulation (PWM) to send signals to the generator circuitry to control the amount of output from the generator. The amount of DC current produced by the generator is controlled by the EVR circuitry contained within the generator.

*****

Voltage is monitored at the B+ terminal stud to insure it is connected. If the B+ cable is loose, the PCM will shut down generator field. Because of this new feature, pin-2 of the field connector is internally connected to the B+ terminal.

The generator used with diesel engines is internally regulated. The generator and ECM communicate for diagnostics, etc. If the generator regulator becomes disconnected from the ECM, it will still operate, but in a default mode.

That's the current system for PETROL engines....... straight from the FSM. The TIPM functions as the "voltage regulator" the alternator itself is simple... i.e. it doesn't have any internal electronics apart from the rectifier diodes.

Yes the control signal for a petrol engine is PWM as stated

The diesel alternators are electrically and mechanically different from the petrol system and use an internal regulator with communication to the Engine control module via LIN.....

So depending on what engine we are working with different technologies are involved.

Hey Guys

2010 CRD here

I have 2 optimas linked up in a dual battery system.

Is there a way to set the alternator to the 14.3 volts default output by unplugging something?

I have relocated both batteries to the rear of the Jeep so I'm not worried about temps.

I usually see 13.9v - 14.2v on my scangauge and would like a bit more juice



EugeJK - I read your post, where is the connector that you unplugged?

In the early CRD days the system would overcharge the CRD's battery so the dealers apparently did a reflash of the TIPM to lower the charge voltage. So technically it is a programmable parameter. However..... the chances of getting a dealer to reverse this i'd guess is pretty low. In most cases they just reflash via a download and going backwards on revisions isn't something they do. Still you could ask..... but given the CRD's history of failed batteries I think they would say no.

IMHO just get a Dc to DC battery management system - at least its a known thing with no downsides except cost :-)