Check Gauges Light - Alternator not charging

Tiny
DCAMIRO
  • MEMBER
  • 2002 DODGE DAKOTA
  • V8
  • 2WD
  • AUTOMATIC
  • 145,000 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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Saturday, November 6th, 2010 AT 2:16 PM

16 Replies

Tiny
KHLOW2008
  • EXPERT
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.
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Saturday, November 6th, 2010 AT 3:18 PM
Tiny
DCAMIRO
  • MEMBER
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!
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Saturday, November 6th, 2010 AT 6:25 PM
Tiny
KHLOW2008
  • EXPERT
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
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Sunday, November 7th, 2010 AT 1:22 AM
Tiny
DANO69R
  • MEMBER
My 02 Dakota is doing the same thing but this time after restarting several times, it acted as if the battery was dead. After disconnecting the battery for maybe 20 or 30 minutes, everything was fine and this time the voltage gauge showed everything was normal. Everything will normally be ok until I don't drive it again for a day and then I have to start this whole process over although having to disconnect the battery has only occurred twice. Usually it's a matter of shutting the truck off and restarting it 5-10 times before everything goes back to normal. I had to replace the PCM with a used one cost me $150.00 all fixed. I love this site.
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Monday, August 17th, 2015 AT 4:55 AM
Tiny
JACOB CARDWELL
  • MEMBER
  • 2002 DODGE DAKOTA
  • 4.7L
  • 4 CYL
  • 4WD
  • 128 MILES
I have replaced battery twice, alternator and had it checked twice and PCM. I can charge battery and truck will start and run like a top, but as soon as battery life goes down the check gauges light comes on and boom trucks dead. So I jumped it with jumper cables and it will start just fine, but as soon as I unhook cables boom it's dead. What else could be the problem? I have checked connections and everything I know to. Please help thanks in advance
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
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.
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)
Tiny
JACOB CARDWELL
  • MEMBER
I will do that this weekend. I did this yesterday on the large cable and it had nothing putting out. Even though I had the truck running with the jumper cables attached to it. The battery is good but stays dead cause it's not getting charge, I will check the 2 small cables while running this weekend
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
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.
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)
Tiny
GREGSMITH545
  • MEMBER
  • 2002 DODGE DAKOTA
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
My alternator is not charging the battery why is that
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
It could be a few things. Have you had it checked at a parts store? Most will do it for free.
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
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
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)
Tiny
BARBARABARN
  • MEMBER
  • 1999 DODGE DAKOTA
Electrical problem
1999 Dodge Dakota 6 cyl Two Wheel Drive Automatic

We changed the thermostat. Unplugged the alternator and moved it out of the way to clean off old gasket. Replaced alternator and plugged in in. Put the belt back on. Now not charging the battery. Any suggestions?
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)
Tiny
BLUELIGHTNIN6
  • EXPERT
Ensure connections are hooked up properly and inspect drive belt tension.

Thanks for using 2CarPros. Com!
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)
Tiny
BARBARABARN
  • MEMBER
[quote="barbarabarn"]Electrical problem
1999 Dodge Dakota 6 cyl Two Wheel Drive Automatic

We changed the thermostat. Unplugged the alternator and moved it out of the way to clean off old gasket. Replaced alternator and plugged in in. Put the belt back on. Now not charging the battery. Any suggestions

We found the problem. Blown fusible link. Replaced it now works great Thank you
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)
Tiny
REDMAN79
  • MEMBER
  • 1999 DODGE DAKOTA
Computer problem
1999 Dodge Dakota V8 Four Wheel Drive Automatic

How can check to see if my ECM is working or not.
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
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.
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Thursday, January 24th, 2019 AT 3:00 PM (Merged)

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