Mechanics

CHECK GAUGES

2002 Dodge Dakota

Electrical problem
2002 Dodge Dakota V8 Two Wheel Drive Automatic 145000 miles

This happened a few months ago and now its happening again. The check gauges light comes on and the battery gauge drops from the middle down to nothing. I replaced the alternator and the battery and got the amps tested and they were coming out low. They exchanged my alternator for another new one and still only about 11 volts instead of the 13.5 or 14 that its supposed to put out. Now, everytime I turn the engine off and back on, the volt gauge goes back to just above low with no check gauges light on and within a few minutes the gauge drops again to nothing and the light turns back on. Truck still starts and runs but the voltage isnt right. Now I was told that the voltage regulator is controlled by the computer. Does this sound like I have it right? Can I bypass the computer and externally control the voltage instead of going through the computer? I want to replace the computer as a last resort. Where can I get an external voltage regulator if it is in fact this that is my problem.
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Dcamiro
November 6, 2010.



Hi dcamiro,

Here is a description of the voltage regulator and you have no alternative except to replace the PCM if the voltage regulator is bad.

VOLTAGE REGULATOR
DESCRIPTION
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.

OPERATION
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.

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. 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 (100 Hz), 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. Also refer to OPERATION for additional information.

KHLow2008
Nov 6, 2010.
I thought I did ask correctly. I need to bypass the PCM so the alternator is ALWAYS on at 13.5 Volts when the engine is running.

How can I do that?

Never say never, ANYTHING is possible!

Tiny
Dcamiro
Nov 6, 2010.
You need to get an alternator that has inbuilt voltage regulator or install an external voltage regulator and rewire the system if you wish to by bypass the PCM.

You stand the risk of the PCM not working correctly and other problems when the PCM is not getting the correct signal from the charging system

KHLow2008
Nov 7, 2010.