Check Gauges Light - Alternator not charging

Hi dcamiro,

It sounds like you have a battery temperature sensor that has gone out or have corroded wiring. Here is the alternator wiring diagrams below with a guide so you can do some testing and get back to us.

https://www.2carpros.com/articles/how-to-check-wiring

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.

Check out the diagrams (Below). Please let us know what you find. We are interested to see what it is.

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

Measure the three voltages on the terminals on the back of the alternator and tell me what you find. The large output wire should have battery voltage on it all the time. The voltages on the two smaller terminals must be measured while the engine is running.

If there is 0 volts on the output stud, the problem is diagnosed. Look for a very large fuse that is bolted into the under-hood fuse box. That is blown, most likely from the original alternator, or it has a loose connection.

To verify this, measure the voltage on that stud on the back of the alternator, with the engine running. You'll find around 14 to 15 volts, but the battery voltage will still be low, at around 12.6 volts. Those two points are supposed to have the same voltage all the time.

It could be a few things. Have you had it checked at a parts store? Most will do it for free.

I'm in pain; why is that?

What is the symptom? Do the headlights dim when trying to start the engine? Is there one loud clunk? Rapid clicking when trying to start the engine? Engine cranks but will not start or run?

Do you have a basic understanding of electronics? If so, this system is extremely reliable and easy to troubleshoot. The most common cause of an alternator problem is worn brushes. These are very easy to replace by a competent do-it-yourselfer.

Caradiodoc

Ensure connections are hooked up properly and inspect drive belt tension.

Thanks for using 2CarPros. Com!

Sorry it's been three weeks since you posted this, but I'm here now. We had a '97 Dakota that I planted a half dozen bugs in for my students to troubleshoot. They found out that this is a very simple circuit that Chrysler made very complicated-looking. It's also very reliable.