Brand new battery, brand new alternator, battery light still on after resetting it

Dandy. You might want to charge the battery at a slow rate for an hour, with a portable charger, but I will be back tomorrow to see if you had the charging system tested. No need to waste time looking for other causes that may not exist until we know the test results.

Check the level of the brake fluid in the reservoir too. If you have to add a little, do not fill it very much or to the top. Be very careful to not get any petroleum product in there, like engine oil or power steering fluid. That would create a very expensive repair.

You cannot test anything else without a professional load tester, but it is irrelevant. 17.8 volts is way too high and is going to destroy the battery and numerous computers and bulbs. The acceptable range is 13.75 to 14.75 volts.

Measure the voltages on the two smaller terminals on the back of the alternator and the larger output stud. The first two must be done with the engine running. I will need to dig up a service manual at home to see where to go next. This charging system is different from what I have memorized.

Is this a Sebring Coupe, Convertible or Sedan The Sedan and Convertible are built on a different chassis than the Coupe and use different wiring.

17.8 is very high for charging but if the battery was faulty it may put out a higher voltage to try to compensate for the problem. Testing for ripple is done by checking for an AC voltage across the battery terminals with the engine running. Load testing requires either a carbon pile tester or a charging system analyzer.

Do you have the domestic convertible or sedan model, or the Mitsubishi-built model?
Here is an article to get you started:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Did you measure the voltages I asked about?

Ripple voltage can be misleading. Digital volt / ohm meters measure AC voltage accurately only at 60 HZ, which is house current. Their accuracy drops way off at higher frequencies. To add to the misery, I've been doing these tests for well over 35 years, but I never used a tester that displayed a voltage for ripple voltage, so I don't know what "normal" is. Every tester I've ever used shows the relative ripple voltage as "low", "high", or somewhere in between. It's not common to find something in between. Normally ripple voltage will be low AND full-load output current will be close to the alternator's rated capacity, or ripple voltage will be high, AND the most you can get on the full-load test is exactly one-third of the alternator's rated capacity. That is caused by one failed internal diode of the six, but that won't result in the severe over-charge condition you found.

I can see that I added some confusion to the story. The diagram shows three wires, plus the output wires, at the alternator. This circuit is different from the simple and common Chrysler circuit that worked well for decades. You have a Mitsubishi alternator with an internal voltage regulator. The regulator can be replaced separately to try to solve the over-charging condition, but the Engine Computer is involved too. In the Chrysler system, the regulator is built into the Engine Computer so it can modify charging voltage according to a number of variables. The Engine Computer in your car also has some say in the desired charging voltage, but I don't know what voltages to expect on the wires. I DO know the computer would never request 17.8 volts. That leaves the voltage regulator or entire alternator as what needs to be replaced.

I am going to guess you have the domestic model. That will have three wires on the alternator to take voltage readings. So we do not overlook anything, start out by measuring the battery's voltage with the engine off. You should find 12.6 volts. If it is closer to 12.2 volts, the battery is run down and should be recharged at a slow rate for an hour or two. If you should find it around 11 volts or less, it has a shorted cell and must be replaced.

Once the engine is running, measure the battery's voltage again and tell me what you find. Go to the large output stud on the back of the alternator and measure the voltage there. It must be exactly the same as what you found at the battery, well, within a tenth or two of a volt.

Next, there is two small wires plugged in on the back. You will need to back-probe through the connector to take those readings because they are only valid when they are plugged in and the engine is running. Tell me what you find on those two.

If you have trouble getting stable readings on the smaller wires, it is because Chrysler changed the layout of the circuit a few years earlier. Operation is the same, but all the voltages we had memorized for the last forty years are different. If your voltmeter's display is bouncing around too much to read, use a test light instead. All we need to know is the relative brightness. Poke it across the battery and you will see what full brightness looks like. Compare that to its brightness on the two smaller wires. Again, these readings must be taken with the engine running.

Hi,

I need you to check the alternator output. On these vehicles, the regulator is integral with the power-train control module (PCM). It isn't a separate component. If charging is not happening when the light comes on, the regulator is most likely bad.

Here is a link that explains how to test an alternator. I need you to first check battery voltage with the engine off. It should be right around 12v. Then test it with the engine running and the light off. It should be around 14v. Last, test it with the light on and let me know the results. Here is a link that will help:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Let me know what you find.

Joe

Acts like the belt is loose. Can you connect a voltmeter to watch what happens when the lights come on? The system voltage must be between 13.75 and 14.75 volts.

Caradiodoc

How does this happen? Does the "battery" light turn on after the engine stalls or does the light come on while you're driving, then the engine stalls a while later? Will it restart with a jump-start? Was the alternator tested while the "battery" light was on? If not, it was tested while an intermittent problem wasn't occurring.

What is the voltage at the battery with the engine running?

Roy

Ok, tighten the lug that the cable is mounted on.

What is the voltage at the battery with the engine running?

Roy