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Old 07-02-2016
EugeJK  EugeJK is offline
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Join Date: Jan 2008
Location: Adelaide
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Default CRD Alternator voltage

Mine is MY08 and just started on its forth D31A battery. They all lasted only ~3 years. I decided to look into the issue and share my findings here.

The alternator is modern type, internally regulated and has LIN bus for diagnostic and control from the ECU, just one wire on the 3-pin connector. My charging voltage has been randomly anywhere from 13.4 to 15.8. The ECU is meant to temperature compensate it 10mV/C. But I just monitored the opposite - the hotter it gets, the higher is the alternator output. The three of my batteries died during or after hot weather. Nothing wrong with either alternator or ECU hardware. It's Chrysler shitty software that killed my batteries. I approached two stealerships, but they had no updates for that. Neither they could tweaked the ECU via OBD2 to change charging voltage.

I worked through documentation on the alternator. It's got an electronics controller inside and for Chrysler it's factory programmed with default voltage of 14.3 that makes sense as this is mid point for D31A recommended charging voltage by alternator (13.6-15.0). If there's no LIN comms with the ECU, the alternator regulates to the default voltage.

So, the solution was to unplug the connector. I got the battery warning light on the dash, but now my charging voltage is dead steady to 14.3 and it works like old school type.
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Last edited by EugeJK; 08-10-2017 at 03:29 PM.

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