2009 Dodge Ram no charge

Tiny
TGWILSON13
  • MEMBER
  • 2009 DODGE RAM
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 2,000 MILES
I have a 2009 Dodge Ram and it will not charge I have put a brand new alternator battery and replaced the PCM and still it won't charge
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Monday, November 16th, 2015 AT 1:44 PM

15 Replies

Tiny
CARADIODOC
  • EXPERT
Measure the voltages on the three wires on the alternator. The large output wire should have battery voltage on it of 12.6 volts with the engine stopped, and it should go up to 13.75 to 14.75 with it running. The voltages on the two small terminals have to be taken with the engine running.
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Monday, November 16th, 2015 AT 2:22 PM
Tiny
TGWILSON13
  • MEMBER
The 2 wires on top are the voltage regulator to the PCM right
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Monday, November 16th, 2015 AT 8:31 PM
Tiny
CARADIODOC
  • EXPERT
Nope. Building the voltage regulator into the generator, like GM and Ford do, insures you have to buy more than what must be replaced. Chrysler never did that. The voltage regulator is inside the Engine Computer where it can adjust charging voltage or turn the alternator off based on air temperature, coolant temperature, wide-open-throttle, and anything else the computer knows. This makes their alternators real simple and the circuit is easy to test.
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Tuesday, November 17th, 2015 AT 4:14 PM
Tiny
TGWILSON13
  • MEMBER
I checked the volts and they are ok but when I turn it on it stays at 12.1 volts and says it's not charging and I have replaced the alternator battery and PCM still they won't charge
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Tuesday, November 17th, 2015 AT 5:36 PM
Tiny
CARADIODOC
  • EXPERT
You gotta be more specific so I can figure out what's working and what isn't. What are you turning on and what stays at 12.1 volts? What are the three voltages on the alternator wires when the engine is running?
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Tuesday, November 17th, 2015 AT 7:30 PM
Tiny
TGWILSON13
  • MEMBER
Ok I re check the connections in on top of the alternator there is a red wire in a black wire the black wire gets 12 volts but the red wire has nothing
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Wednesday, November 18th, 2015 AT 12:14 PM
Tiny
TGWILSON13
  • MEMBER
And the big wire that goes to the alternator reads 11.9 volts
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Wednesday, November 18th, 2015 AT 12:16 PM
Tiny
TGWILSON13
  • MEMBER
And when its off it has 12 volts to it but the top two wires have no voltage when it is off
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Wednesday, November 18th, 2015 AT 12:17 PM
Tiny
TGWILSON13
  • MEMBER
And I checked the wire that goes through the harness from end to end on the red wire that doesn't get no voltage and it's there's no brakes anywhere whenever I tested it with my voltmeter
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Wednesday, November 18th, 2015 AT 12:25 PM
Tiny
TGWILSON13
  • MEMBER
I really appreciate all the help that you can give me thank you once again it's all just been working on trying to figure out why it won't charge for about 3 months now I've gone through about for PCMs 3 alternators and two batteries and still can't figure it out
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Wednesday, November 18th, 2015 AT 3:32 PM
Tiny
CARADIODOC
  • EXPERT
The two small wires won't have voltage until the engine is running. I need to know what you find on them when the engine is running. In particular, the brown / gray wire has to have something, but I haven't worked on this new system so I don't know if it's a voltage or a square wave pulse. If you find 0 volts with a digital voltmeter, or if the reading is bouncing around, check it with a test light. According to what I've been reading, this is the only control wire so you'll rarely find full battery voltage on it, if ever. A digital voltmeter will get confused with a pulsing square wave, but a test light will smooth it out and give you a better indication. I think the light should be dimmer than when it's connected to the battery.
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Monday, November 23rd, 2015 AT 6:46 PM
Tiny
TGWILSON13
  • MEMBER
Ok with the truck on the brown and gray wire has no vvoltage but the other one has 12 volts
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Tuesday, November 24th, 2015 AT 8:09 PM
Tiny
CARADIODOC
  • EXPERT
This is exactly backward from what I've been reading. Just to double-check, your voltmeter's negative probe should be on ground or the battery's negative post, not on the positive post.

After conferring with a former student, there will not be a steady DC voltage on the brown / gray wire feeding the field winding in the alternator. That will be a square wave and its "duty cycle" will be varied to adjust output current. That will confuse a digital voltmeter so it won't read correctly. The red / gray wire carries the signal back to the computer that tells it the alternator is working. Either the 12 volts you found there is saying the alternator is working or you have the voltmeter grounded to the wrong place.

What is the voltage right on the large output stud on the back of the alternator when the engine is running?
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Wednesday, November 25th, 2015 AT 5:28 PM
Tiny
MICHAEL KUPHAL
  • MEMBER
Some going to finish this thread?
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Friday, December 22nd, 2017 AT 4:47 AM
Tiny
CARADIODOC
  • EXPERT
If you have a question, please start a new post specific to your vehicle, and be sure to list the engine size, transmission type, and mileage. Hopefully you will do a better job of reading voltages while the engine is running. I need those to know exactly what is working and what isn't.
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Friday, December 22nd, 2017 AT 11:47 AM

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