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Dashboard lights on and off, battery light on and off

Tiny
SIH2442
  • MEMBER
  • 2014 CHRYSLER 200
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
Hi! We recently changed the alternator in my car. Immediately after the dashboard lights were going on and off but the car was driving fine. It eventually stopped and was driving completely fine. But today I went to drive and it started happening again. The lights were flashing on and off, battery light on, all electrical systems going in and out; radio, air, lights, turn signal, speedometer not working etc. This time there were longer pauses between when it went out. We decided to test the battery and it was around 12 volts when the car wasn’t on, went to 14 when just starting the car, but we noticed when the battery light came on in the car it shot up to around 16. What could be the reason for this?
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Tuesday, August 20th, 2019 AT 6:02 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Welcome to 2CarPros.

If it shot up to 16V, that is too high and can cause electrical damage. Now, you replaced the alternator, which appears to be working. It is my believe that the problem lies in the power-train control module (PCM) and here is why.

Most cars have a voltage regulator built into the alternator. On this vehicle, the voltage regulator is built into the PCM. If that fails, it will either not charge or as in this case, overcharge. This can be dangerous because it can overheat electrical wiring or components and lead to a fire.

What I recommend is this. Unless you are really knowledgeable with automotive wiring and have the proper test equipment, I would have it inspected by a knowledgeable tech. Normally, I try to explain what needs check and how to do it, but in this case there are risks.

I attached a portion of the charging system wiring schematic so you can see that power comes in to the alternator (generator on schematic) via the starter, and then it splits off to the PCM. Two wires enter the PCM. The "gen fld ctrl" is where power is regulated.

Let me know if I can help or if you have other questions.

Take care,
Joe
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Tuesday, August 20th, 2019 AT 7:16 PM
Tiny
SIH2442
  • MEMBER
  • 2 POSTS
Thank you for the reply! That’s very helpful. Could it be that even if the battery isn’t at 16 constantly? The battery light goes on and off along with the rest of the electrical system. But for about a week the light didn’t come on and everything worked perfect.
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Tuesday, August 20th, 2019 AT 8:25 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Welcome back:

It is possible. The PCM controls a lot of electrical components, so I have a feeling that is where the problem lies. And yes, it is possible that it isn't always at 16v.

Let me know if I can help in any way.

Take care,
Joe
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Tuesday, August 20th, 2019 AT 8:33 PM

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