The battery light is on?

Tiny
DARKCALISTO
  • MEMBER
  • 2014 FORD FOCUS
  • AUTOMATIC
  • 89,000 MILES
I live in Texas and I need to get my car inspected. Recently my battery light keeps coming on. There is no sign that there is any problem with the car itself. I replaced the battery just in case and it's working great. The light turns off sometimes when it's cold out but comes back on after I have been driving for a while. My check engine light and my battery light are two different lights on my dash and the check engine light is off. Can I pass inspection without fixing whatever is causing this problem with the battery light?
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Tuesday, March 19th, 2019 AT 4:26 PM

35 Replies

Tiny
CARADIODOC
  • EXPERT
Why would you want to risk sitting on the side of the road? There seems to be a lot misconception about the "Battery" warning light. It has nothing to do with the condition of the battery. That light refers to the charging system that keeps the battery recharged after starting the engine, and it supplies all the electrical power to the car. Intermittent failures like you described are fairly common. The most common cause is worn brushes inside the generator, although it's a little early for the mileage you listed. Worn brushes fail to make a solid contact, and as they wear more, the problem will occur more often and for longer periods of time. This can go on for weeks or even months. Once the failure becomes permanent, the battery will have to provide the electrical power by itself, and it can only do that for up to an hour.

A wiring problem can cause this too, but it is much less common. The typical causes are corroded connector terminals, and even spread terminals in the fuse box for the fuse for the generator.

Here's a link to an article about testing the charging system, but it's important to understand any testing has to be done while the warning light is on. Everything is working properly when the warning light is off, so there's nothing wrong at that time.

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

There's more involved testing that requires a professional load tester, but that isn't really needed for this problem. The best test you can do yourself is to measure the battery voltage with the engine running, when the warning light is on. Besides a no-charge condition, the light on your car will also turn on for a low-charge or an over-charge condition. All of those can be identified by the battery voltage reading. An over-charge condition is probably the least common of failures, but that won't take long to damage the battery.

This article explains how to use a digital voltmeter:

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

The meter shown is an "auto-ranging" meter that selects the proper range on its own. Many voltmeters have a switch that allows you to select the range you want to use. The best one for this purpose is the "20-volt DC" range. On that range, the meter will read anything between 0.00 volts and 19.99 volts. That will cover anything on your car, and with the most accuracy.
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Tuesday, March 19th, 2019 AT 4:55 PM
Tiny
RLAW91
  • MEMBER
  • 2005 FORD FOCUS
  • 2.0L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 112,500 MILES
About a month ago, I noticed that my battery light on my dashboard came on. Within a few days, I felt the car slowly losing power and eventually once even shut off. I took it to a local mechanic and had it tested, for them to say that I had no issues, but my battery was testing on the lower side so they recommend that I replace it, which I did. However, a few days later my car started doing the same thing (losing power, battery light still on), so I returned to the mechanic where they ended up having to replace my alternator as well. Now, a few weeks later, my battery light still comes on and I still feel as if my car isn't using as much power as it should, especially when I'm idle or at a stop. The car even sputters sometimes and has an intention vibration whenever I'm sitting still (in park or in drive). PLEASE HELP.
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Friday, June 12th, 2020 AT 12:16 PM (Merged)
Tiny
KNOWLEDGE IS POWER
  • EXPERT
It sounds like the alternator was your problem the entire time and the rebuilt one they installed has gone bad, I would replace it with a Motorcraft unit here is a guide to walk you through the steps and instructions for your can in the diagrams below.

https://www.2carpros.com/articles/how-to-replace-an-alternator

Check out the diagrams (Below). Please let us know what happens.
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Friday, June 12th, 2020 AT 12:16 PM (Merged)
Tiny
PROSPECTOR01
  • MEMBER
Thank you for this post I had this problem had to get a motorcraft unit from Amazon for $143.00 fixed it! I love this site.
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Friday, June 12th, 2020 AT 12:16 PM (Merged)
Tiny
C3DADDYO
  • MEMBER
  • 2005 FORD FOCUS
Ford Focus 05, milage 32000, 2.0 engine.

I changed the battery in my Focus. Now the battery light on the dash stays on even when the car is off. I checked all the fuses. What else could be causing this? Also, how would I disconnect the little flashing LED that the dealer installed to look like an alarm system?
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Friday, June 12th, 2020 AT 12:16 PM (Merged)
Tiny
JET1000
  • MEMBER
We had the same problem in ours, replaced battery and alternator, still stayed lit up. Hubby checked fuses in fuse box in engine, there was a burnt out fuse there, replaced it and light went off.
Hope that solves it.

Good luck!
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Friday, June 12th, 2020 AT 12:16 PM (Merged)
Tiny
BDOYLE53
  • MEMBER
  • 2005 FORD FOCUS
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 62,000 MILES
My battery light keeps coming on, I have checked belts, battery and all connections. Next step is my alternator. How can I check it without having to go completly through the process of removing it and then finding out it is ok?
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Friday, June 12th, 2020 AT 12:16 PM (Merged)
Tiny
DAVE H
  • MEMBER
Generator On-Vehicle Tests - Load Test
Switch the tester to the ammeter function.
Connect the positive and negative leads of the tester to the corresponding battery terminals.
Connect the current probe to the generator B+ output terminal, circuit 30-BA6 (RD).
With the engine running at approximately 2,000 RPM, adjust the tester load bank to determine the output of the generator. Generator output should be greater than the graph shown below in order to pass this test. If the test is passed, refer back to the pinpoint test or GO to SYMPTOM CHART. If the test is not passed, install a new generator. For additional information, refer to GENERATOR AND REGULATOR .
Fig. 11: Generator Output Graph
Courtesy of FORD MOTOR CO.


http://www.2carpros.com/forum/automotive_pictures/266999_focus_2.jpg



Generator On-Vehicle Tests - No Load Test
Switch the tester to the voltmeter function.
Connect the voltmeter positive lead to the generator B+ terminal, circuit 30-BA6 (RD) and the negative lead to ground.
Turn all electrical accessories off.
With the engine running at approximately 2,000 RPM, check the generator output voltage. The voltage should be between 13.0 and 15.0 volts in order to pass this test. If the test is passed, refer back to the pinpoint test or GO to SYMPTOM CHART. If the test is not passed, install a new generator.
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Friday, June 12th, 2020 AT 12:16 PM (Merged)
Tiny
JULIESCLOWN
  • MEMBER
  • 2005 FORD FOCUS
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 118,000 MILES
Battery light came on and I cleaned connections. Started car light came on in seconds so I checked battery voltage it was 12.4. Started car and then checked voltage it was 12.5 and then dropped. I charged battery to 12.8 and then started car checked voltage 4 times while running voltage dropped each time to 12.3. Wiring seems tight and ground seems good. Do you think I should change alt.
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Friday, June 12th, 2020 AT 12:16 PM (Merged)
Tiny
RENAUDTN
  • MEMBER
It does sound like an alternator problem indeed. Have it checked at your local auto part store.
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Friday, June 12th, 2020 AT 12:16 PM (Merged)
Tiny
SKYGOG1310
  • MEMBER
  • 2005 FORD FOCUS
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 101,000 MILES
My battery light comes on occasionally for a few seconds when I run my air conditioner. It doesn't happen when the a/c isn't running.
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Friday, June 12th, 2020 AT 12:17 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Have the alternator load tested with a VAT machine-Sounds like its not compensating for the additional load from the AC
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Friday, June 12th, 2020 AT 12:17 PM (Merged)
Tiny
SKYGOG1310
  • MEMBER
That makes sense. Thank you very much.
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Friday, June 12th, 2020 AT 12:17 PM (Merged)
Tiny
TONYB121707
  • MEMBER
  • 2004 FORD FOCUS
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 99,815 MILES
Battery light on (but very dim) stays on while running while key is in off position, does not flicker get brighter get dimmer just stays very dim no matter if the car is running or turned off, replaced alternator last year and replace battery 3 days ago, all fuses are good all connections good car starts and drives without stalling but light stays on
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Friday, June 12th, 2020 AT 12:17 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
Unplug the connector on the back of the generator. If the light goes off, the voltage regulator is not turning off. Replace either the regulator or the entire generator. On the unlikely chance the light stays on when the regulator is unplugged, the green / red wire is grounded someplace. A dead short should cause the light to be bright so you would not be looking for a dead short. You'd be looking for the wire melted to another wire. Even that isn't likely.
Be sure to check all connectors and grounds for good contact

caradiodoc

Attached below is the wiring diagram for your charging system
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Friday, June 12th, 2020 AT 12:17 PM (Merged)
Tiny
DAVIDCHIARAVALLI
  • MEMBER
  • 2004 FORD FOCUS
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 125,000 MILES
I have a ford focus zx5 2004. My engine shook then my oil light came on and went to the red. Then my check engine light came on and my battery light came on. Whats wrong with my car?
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Friday, June 12th, 2020 AT 12:17 PM (Merged)
Tiny
RIVERMIKERAT
  • MEMBER
Does the engine still run? Your engine shaking tells me something internal might have broken, or a motor mount broke. Have the computer scanned for codes in the memory. Use a voltmeter to check the voltage in the battery. Have the battery load tested to see if it holds a charge. The oil light being on normally means that the sensor is not detecting oil pressure. Make sure there is oil in it. Remove the valve cover and crank the engine over. You should see oil flowing on top of the cylinder head. No oil flow means a faulty oil pump.
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Friday, June 12th, 2020 AT 12:17 PM (Merged)
Tiny
ANOSAL
  • MEMBER
  • 2003 FORD FOCUS
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 10,500 MILES
The battery light recently came on so I checked the voltage and saw that the voltage hung around 12.5 while the car was off and on. The serpentine belt was in good shape and the wires were in good shape so I decided to replace the alternator. I replaced the alternator using the Haynes recommended 33 ft-lbs torque and the cars voltage remained 12.5 area while running. Then I replaced the battery which I planned to do anyways because it was about five years old, that didn't change a thing. Any help or tests would be appreciated.
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Friday, June 12th, 2020 AT 12:18 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Hi anosal, Welcome to 2carpros and TY for the donation

Check and test fuse no. 10 10amp and fuse no. 61 7.5amp if both fuses are okay -have the computer controlled field generation circuit checked and tested.

See below:


http://www.2carpros.com/forum/automotive_pictures/12900_alty_70.jpg

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Friday, June 12th, 2020 AT 12:18 PM (Merged)
Tiny
AWALKER
  • MEMBER
  • 2003 FORD FOCUS
2003 Ford focus, 78,000 miles, 2.0 zetec. My battery light comes on at 35 mph. And will go off at 55 mph. It does not have any other symptoms or noises. I chked the battery with a volt meter and it chked ok. No other engine lights have come on. I have changed the drive belt and chked all connections. What could this on off battery light mean?
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Friday, June 12th, 2020 AT 12:18 PM (Merged)

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