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Intermittent Battery icon lamp

Discussion in 'Neon' started by AllanC, Sep 24, 2016.

  1. AllanC

    AllanC Well-Known Member

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    Vehicle is a 2003 Dodge Neon, 2.0 liter 4 cylinder engine, 4 speed automatic transaxle. Odometer reading is 290,000+ miles. On Aug 20, 2016 I had to replace the battery due to a weak cell. The starter was laboring in spinning the engine. A battery test at a local auto parts store confirmed a weak cell. Battery was 5 years old so it was not completely unexpected.

    After replacing the battery and driving the vehicle, the red battery icon lamp illuminated. In the 12 years of owning the vehicle I have never had problems with this lamp illuminating. I used a volt ohm meter to check the charging voltage with engine running at idle. Voltage was 13.0 volts. I used a scan tool and found no diagnostic codes associated with battery charging in the PCM (powertrain control module). I concluded that the alternator was not at fault the charging voltage with engine running at idle. Voltage was 13.0 volts.

    On Sep 21 the battery icon lamp turned on again. Now it seems more consistent in staying illuminated. Yet I have had no problems in starting and running the vehicle and using all accessories. Last night Sep 23 on a 15 minute trip with vehicle lights and air conditioning operational, I barely made it home with headlamps dimming, air bag lamp illuminating, instrument cluster gauges sweeping clockwise and counterclockwise. Turned engine off and attempted to restart vehicle. Dead battery.

    There are no diagnostic codes in the PCM related to alternator charging or low system voltage. Today I charged the battery. At engine idle volt meter only shows 12.2 volts. So the alternator is not charging. Local Advance Auto tested the charging system and came to the same conclusion: failed alternator. But I am not so sure. Maybe the field control circuit that regulates the alternator field has an issue - excessive resistance, poor connection, broken wire. The wiring schematic for this vehicle shows a fusible link in the wire that connects the alternator output terminal to the battery wire at the starter. I need to make sure that link has not failed.

    I want to test the field control circuit. The wiring schematic shows the PCM switches the power side to the generator field. The return wire from the field goes to ground. Can I use a test lamp with one wire connected to engine ground and the other test lamp probe touched to the control wire from the PCM to the generator field? I do not want to overload the PCM generator field driver circuit but need to check that the PCM is supplying electrical power to the field.
     
  2. ImperialCrown

    Level III Supporter

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    A test light should be a low load for the PCM field current. It shouldn't hurt anything to see what is there voltage-wise.
     
  3. PCRMike

    PCRMike Well-Known Member

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    Keep in mind, worn out brushes in the alternator can cause exactly this. I have seen it many times on many vehicles. Change either the brushes or the alternator.
     
  4. AllanC

    AllanC Well-Known Member

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    Good reminder point. Slip ring brushes can wear sufficiently that spring pressure is reduced and cannot maintain proper electrical contact between the rotating ring and the stationary brush. On OBD I vehicles that could produce code 41 - alternator field circuit. On OBD II vehicles such as this Neon one would expect a code with the generator field circuit and/or low battery voltage. Unfortunately I have no diagnostic codes in the PCM. So the condition is intermittent and does not meet the duration criteria for setting a diagnostic code.

    What is frustrating is that logic has been added in the PCM to detect an electrical problem and turn on the battery icon lamp. But no code. So one has to methodically check and follow hunches as to what could possibly be the problem.

    The alternator is not easily accessible since it is mounted low on the engine block and close to the firewall. I want to be absolutely sure it is an alternator failure before removing it.
     
  5. PCRMike

    PCRMike Well-Known Member

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    After years of experience with fleet management of different brands, and several high miles Neon and Breeze, I would bet a steak dinner on it.
     
  6. AllanC

    AllanC Well-Known Member

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    Well I guess someone owes you a steak dinner :)

    I checked the battery terminal at the alternator and it had 12 volts. So that told me the electrical cable between the alternator and starter battery terminal was good. No problem with the internal fusible link. I checked the alternator field control circuit between the PCM and the alternator and it was good with no shorts. I checked the resistance on the 2 terminals at the alternator for the field circuit. Open circuit when you would expect several ohms. So that was the problem.

    I had previously replaced the alternator 5 years ago at 164,000 miles. I had a lifetime warranty on the unit so the replacement did not cost me any money. Cost was frustration and my time. Replaced the alternator, system charging properly at 13.64 volts and no battery icon lamp illuminated.

    I really got "slammed" on this diagnosis. I would not expect the alternator to develop an intermittent charging condition within 1 day of replacing the battery. What a coincidence! Voltage checks showed the alternator putting out 13 volts to the battery at idle. That was within limits that I would expect There were no diagnostic codes in the PCM indicating low charging voltage or an intermittent field condition in the alternator. I even checked the ohm resistance in the battery temperature sensor thinking that might be causing the problem but it met specifications.

    Twice each week the car is driven on a 120 mile highway trip and all accessories including air conditioning were in use. No problems with vehicle operation or starting. It took a complete failure of the alternator (still no diagnostic codes) to get me onto the right track of diagnosis. So one is never too old to experience bizarre operational conditions.
     
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  7. Doug D

    Doug D Virginia Gentleman

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    Years ago I had a '86 GTS. I can't remember the symptoms it was having, but I ended up taking to a nearby shop. He diagnosed it as a weak battery and installed a new battery. Picked it up and by the time I got home (less than a mile away) the voltage meter was below 12 volts. Took it right back and left the engine running to show him. He couldn't believe it. He said when he tested it, it showed 13+ volts. Long story short, a new alternator was installed.
     
  8. pt006

    pt006 Active Member

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    Allen; back in the day of Chrysler alternators; the brushes were spring loaded and there was a short soft copper wire that carried the current to the field and ALSO limited the brushes travel to prevent the brushes from getting too thin and jamming up inside. Pretty clever!

    Doug; my electric start lawnmower started easily after months of sitting thru a cold New England winter. Mowed for 15 minutes. Stopped to talk to a friend next to the road. [note that the road is the farthest point from and uphill to the garage]. 10 minutes later I turned the key. Nothing. Not even a click from the solenoid.
     
  9. pt006

    pt006 Active Member

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    so, I push the mower to the garage, run a jumper from the battery pos terminal to the solenoid 'start' coil terminal. Nothing. Not even a click. Ah haa; Solenoid coil must have gone bad. Rush to store before closing time. Come home. Install solenoid. Nothing. Get out test light. Test the light. Nothing. Wiggle the wires and bulb. Nothing. Open hood on car. Test light works!!! Retest light on mower battery. Nothing, not even a dim glow. Put a jumper battery on the mower. Fires instantly. Replaced the battery and it's been fine ever since. -------But why me??? -------
     
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  10. PCRMike

    PCRMike Well-Known Member

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    Glad it got fixed buddy!
     
  11. AllanC

    AllanC Well-Known Member

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    Murphy's Law: Anything that can go wrong, will go wrong. Murphy is equal opportunity; no discrimination.
     
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  12. AllanC

    AllanC Well-Known Member

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    I will add some interesting phenomena that I observed with the battery icon lamp on the Neon. I reported on Tuesday, Sep 27 that I had fixed the problem. Intermittent alternator charging which turned into permanent no charge. Replaced alternator. All is good. Lamp has not turned on for several days after replacement.

    On Friday afternoon I had to give a jump start to another vehicle with a dead battery. So I attach battery cables from the Neon battery to the disabled vehicle all the while making sure I observed correct polarity. I had to run the Neon at fast idle for a few minutes to get sufficient charge into the dead battery so that vehicle would start. Finally get disabled vehicle to crank and start.

    Disconnect jumper cable and re-enter the Neon. Battery icon lamp illuminated. $#@%$@$/. How could a jump start cause an electrical problem??? Turned off the Neon engine, restart and battery lamp not illuminated. But it typically waits several minutes, senses a problem and then turns on the lamp. I used a volt-ohm meter and verified I still had good charging at 13.5 volts from the alternator. Car was driven 120 miles on Saturday and no electrical issues.

    So I am thinking that when the Neon battery was collected properly (in parallel) to the dead battery, the sudden voltage drop and load placed on the Neon electrical system caused the engine management software to detect an abnormal condition and turn on the battery icon lamp. Obviously engine management software can detect abnormal conditions so you have to be alert and think through all the possible situations and actions you do to understand false warnings.

    I talked about Murphy in a previous post. Maybe this is revenge :)
     
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  13. pt006

    pt006 Active Member

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    Allan; Your reasoning sounds good to me. Glad all seems OK now. Take a couple of nitroglycerin pills and things will be back to normal.
     

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