Brake and battery lights on

Tiny
ERIKA WALTERS
  • MEMBER
  • 2004 CHRYSLER SEBRING
  • 3.0L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 140,000 MILES
When I was driving yesterday, on my dash, the brake and battery light came on. What could be the problem?
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Monday, April 3rd, 2017 AT 8:08 PM

8 Replies

Tiny
CARADIODOC
  • EXPERT
Start by having the charging system tested by a mechanic, not at an auto parts store. Tell me what they find for "full-load output current", "charging voltage", and "ripple voltage". The test just takes a few minutes.

Is that the red "brake" warning light or the yellow "anti-lock" brake system light?
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Monday, April 3rd, 2017 AT 8:11 PM
Tiny
ERIKA WALTERS
  • MEMBER
It is the red brake light.
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Monday, April 3rd, 2017 AT 8:13 PM
Tiny
ERIKA WALTERS
  • MEMBER
My dad tested the alternator and it is putting out 17.8 at idle. He wants to know how to test the ripple voltage and the full load output current?
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Monday, April 3rd, 2017 AT 8:17 PM
Tiny
CARADIODOC
  • EXPERT
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.
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Monday, April 3rd, 2017 AT 8:19 PM
Tiny
CARADIODOC
  • EXPERT
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.
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Monday, April 3rd, 2017 AT 8:23 PM
Tiny
STEVE W.
  • EXPERT
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.
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Friday, April 7th, 2017 AT 10:34 PM
Tiny
ERIKA WALTERS
  • MEMBER
It is the limited coupe
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Saturday, April 8th, 2017 AT 5:40 PM
Tiny
CARADIODOC
  • EXPERT
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.
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Saturday, April 8th, 2017 AT 7:26 PM

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