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1995 Plymoth Neon Alt wont charge Battery HELP!


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thebsuguy
New User

Sep 8, 2011, 5:24 PM

Post #1 of 4 (3233 views)
post icon 1995 Plymoth Neon Alt wont charge Battery HELP! Sign In

Hello, And thank you for taking the time to help me!

Here is my problem. Going to be as detailed as i can, so bare with me please!

About a month ago, my speaker had been making some funny sounds for no reason at all, and a week later, it stops. two week later, my car wont start due to no charge in battery. (I do not know if speaker thing has anything to do with it, just including details).

My problem is I have a good Battery, and Good Alternator. But the alternator WILL NOT charge the battery! Battery light IS on.

Car Details:
1995 Plymoth Neon

These are the steps I have Taken:
-Put Battery on a low charge for a few hours, and then was able to drive the car in to get battery checked. Battery is GOOD.

-Pulled the altinator out and got it checked. Altinator is GOOD.

-Checked EVERY fuse. All was GOOD.

-Checked all wires and connections on wire harness from altinator to PCM box. all looked GOOD.

-Checked all connections to the battery, ALL was GOOD.

-Pulled out my CD player to check all connections to make sure it wasnt shorting out some where. All was GOOD.

-Haynes Repair Manual suggests that I check the engine CODEs by doing some funky stuff. And then the Check Engine Light is suppose to blink them out...I HAVE NO IDEA WHAT ITS BLINKING. CAN YOU TELL?
http://www.youtube.com/watch?v=l7iOTmtCiwc
To me it looks like: 1 2 4 1 5 5 .
This mean CODE 12, 41, 55?
If so, this is what the codes are, NO idea how to fix them, please suggest.
CODE 12: Problem with the battery connections. Direct battery input to PCM disconnected within the last 50 ignition key-on cycles.
CODE 41: Problem with the charging system. an open or shorted condition detected in the generator field control circuit.
CODE 55: Completion of Fault Code display on CHECK ENGINE lamp. this is an end of message code.

-Check the conductivity of the Fusible Link from altinator to starter by probing the wire. It was GOOD.

-Checked the wireing from Altinator to Automatic Shut Down Relay, All was GOOD.


PLEASE HELP! I am Clueless what to try next! Could you please give me detailed suggestions of what else I might try? Also, maybe you could give the engine CODEs a shot? (video listed above).

Thank you!


(This post was edited by thebsuguy on Sep 8, 2011, 5:31 PM)


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Sep 8, 2011, 5:58 PM

Post #2 of 4 (3205 views)
Re: 1995 Plymoth Neon Alt wont charge Battery HELP! Sign In


Quote
CODE 41: Problem with the charging system. an open or shorted condition detected in the generator field control circuit.


You need to inspect this circuit (dark green wire). Chrysler did a dumb thing and put the alternator's regulator inside the engine computer. The engine computer commands the charging of alternator by duty cycling the field ground circuit. When the field circuit is grounded by the engine computer the alternator charges.

You can back probe the field circuit at the engine computer connector with a volt meter to see if the engine controller is even attempting to toggle the voltage to ground. Using a oscilloscope is even better when checking this type of circuit out. If the regulator is bad, you have to replace the engine computer.





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thebsuguy
New User

Sep 8, 2011, 6:27 PM

Post #3 of 4 (3194 views)
Re: 1995 Plymoth Neon Alt wont charge Battery HELP! Sign In


In Reply To
You can back probe the field circuit at the engine computer connector with a volt meter to see if the engine controller is even attempting to toggle the voltage to ground. Using a oscilloscope is even better when checking this type of circuit out. If the regulator is bad, you have to replace the engine computer.


First, Thank you!

I was afriad that it was the Computer, But seems like you hinted on the right direction.

However, Im a little fuzzy on how I would go about testing this. my knowledge is limited.

I Did check the Dark green wire from the alternator up to the computer, passing the Automatic Shut down Relay.

You stated "When the field circuit is grounded by the engine computer the alternator charges."

Does this mean Starting the car, and check to see if the Dark Green wire is grounded? And if it is, its working properly, if not, time to buy new computer? is this correct?

If you could, go in as much detail as you are able to on how I would go about checking this!

Thanks!


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Sep 8, 2011, 8:28 PM

Post #4 of 4 (3162 views)
Re: 1995 Plymoth Neon Alt wont charge Battery HELP! Sign In

You really have to check the field ground circuit at the computer itself. The connector has to be plugged in of course or the engine doesn't run, so you have to back probe connector on PIN 41 dark green with a paper clip or small needle. Connect the red lead of your meter to the back probe and ground the black lead to the battery negative post.

Set your meter for DC VOLTS on a scale so you can view 12 volts.

When you have your meter connected this way you are reading the voltage dropping through the computer and the wiring back to the battery negative. This means that when the computer wants to turn the alternator on you will see a low voltage. When the computer isn't turning on the alternator you will see battery voltage (around 12-13 volts). If you see 12 volts dropping through the computer, that means the computer isn't doing anything and you probably have a faulty regulator inside the computer. That's as long as the computer is monitoring electrical system voltage and is sensing the battery temperature through the battery temperature sensor.

The computer is going to pulse the ground, so your meter is going to average out the voltage reading. The meter does this because it isn't fast enough to display the actual voltage reading when voltage is being modulated. Let's say the computer wants to have the alternator put out 50% power. That means you'll see an average of 6-7 volts on your meter.

If you ground that wire, that will full field the alternator and cause the alternator to charge at full power. Voltage on a full fielded alternator can get up to 15 volts with it cranking out an ass load of amps. You have to be careful if you do that because you don't want to cook any of your electronics leaving it like that too long, but that is one way to see if your alternator is able to charge.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.






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