Battery Light is On?

Tiny
LINDSAYB87
  • MEMBER
  • 2003 FORD FOCUS
  • 112,000 MILES
I have a 2003 Ford Focus SE. 4 Cylinder. The battery light has been coming on for a few months, it will come on, and go off. I can hear a difference in the engine when the light comes on.I took it to a auto parts store and had them do a diagnosis on it, the guy said something about the diodes not charging/holding a charge. Last weekend I took it to a mechanic who did another diagnostic test and said the battery is fine, the starter is fine, and the alternator is fine. They were unable to tell me what the problem was because the battery light wasn't ON when I brought it in.I've had the car about 7 years and i've never changed spark plugs or O2 sensors, which are things the mechanic said it could be. Can you shed any light for me?
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Thursday, September 12th, 2013 AT 6:07 AM

19 Replies

Tiny
WRENCHER1
  • MEMBER
It sounds like you have a alternator that is going out which is common to be intermittent. Here is a guide to help you see what you are in for when doing the job.

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

You will need to remove the serpentine belt.

https://www.2carpros.com/articles/replace-serpentine-belt

Check out the diagrams (Below)

Please let us know if you need anything else to get the problem fixed.

Cheers
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Friday, June 12th, 2020 AT 12:18 PM
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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Wednesday, November 25th, 2020 AT 9:01 AM (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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Wednesday, November 25th, 2020 AT 9:01 AM (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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Wednesday, November 25th, 2020 AT 9:01 AM (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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Wednesday, November 25th, 2020 AT 9:01 AM (Merged)
Tiny
DESHON01
  • MEMBER
  • 2003 FORD FOCUS
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 53,000 MILES
Hi, my battery indicator light just came on today. It comes on about 30 seconds after I start my car. I retightend my battery cables which really wasen't loose to begin with. I've started and restarted my car over and over today, and tonight, and it seems to be starting ok. Should I chance it and drive to work tomorrow? What should I do?
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Wednesday, November 25th, 2020 AT 9:03 AM (Merged)
Tiny
BLUELIGHTNIN6
  • EXPERT
Your alternator is most likely starting to fail. Your vehicle runs using the alternator, only uses the battery to start or uses the battery as back up if the alternator does fail during driving. Most part stores will test your charging system free of charge. I suggest having your battery and alternator tested.
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Wednesday, November 25th, 2020 AT 9:03 AM (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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Wednesday, November 25th, 2020 AT 9:03 AM (Merged)
Tiny
JWALTH02
  • MEMBER
I would suggest taking it to an autozone or checker when you get the time and have them test the battery and altenator. You might have a bad altenator if it's dropping while driving at the lower speed since it's using power but when you ramp up the speed it makes up for the drain. So just take it in and have them hook it up for free.
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Wednesday, November 25th, 2020 AT 9:03 AM (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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Wednesday, November 25th, 2020 AT 9:03 AM (Merged)
Tiny
2CEXPT
  • 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:


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

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Wednesday, November 25th, 2020 AT 9:03 AM (Merged)
Tiny
BKHOMEMAKER
  • MEMBER
  • 2003 FORD FOCUS
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 126,141 MILES
2003 ford focus se starts and runs but check engine light, and sometimes battery light comes on. A mechanic want to be stated it needs a head gasket but I think it may need more than that, from what I stated what do you think. Tired of driving Mom's car

BKL
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Wednesday, November 25th, 2020 AT 9:03 AM (Merged)
Tiny
DRCRANKNWRENCH
  • EXPERT
If the check enginne light is on, go to another mechanic and have them use an On-Board Diagnostid, (OBD) reader which will tell the mechanic the error codes that are triggering the check engine light.
As far as the battery light, the diagnostic might bring an error code that explains that as well.
As far as the head gasket, I would need to know why he thinks it needs it. Usually things like poor performance, smoke in the exhaust and milky engine oil are signs of a leaking head gasket.

Getting the error codes from an OBD will gi ve you more insight into the problems that the car has.
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Wednesday, November 25th, 2020 AT 9:03 AM (Merged)
Tiny
TAYLORG165
  • MEMBER
  • 2003 FORD FOCUS
  • 2WD
  • AUTOMATIC
  • 196,000 MILES
Hi, I have the car listed above Zx3. My battery light comes on randomly when I m driving sometimes when I just start the car. I had the battery tested and the battery is good as well as having my alternator which is also good. I do not know what could be causing this. As well as sometimes all the needles on my dash spin all the way around and go wacky and my lights will flicker. My left headlight blew twice when this happened. Any ideas what s going on with my car?
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Wednesday, November 25th, 2020 AT 9:03 AM (Merged)
Tiny
CARADIODOC
  • EXPERT
This is an intermittent problem, so any testing has to be done while the problem is occurring, otherwise everything is going to test okay.

This type of problem is usually caused by a failing generator, and this type of failure is most commonly attributed to worn internal brushes that are making intermittent contact. This can be expected at the mileage you listed.

The warning light can be misleading. It's not related to the condition of the battery. It means the charging system is not keeping the battery charged while you're driving, and that involves the generator and its built-in voltage regulator. In your application, the voltage regulator turns the "Battery" warning light on during a no-charge condition, like on all other cars, but also for an under-charge or an over-charge condition. Voltage regulators can fail in multiple ways. One way results in system voltage going too high. That might explain the bulbs flickering and burning out.

Corroded connector terminals can cause all the same intermittent symptoms as a failing generator. Check for corrosion or spread terminals in the connector at the rear / side of the generator. If you follow that wire harness, there is usually another two-wire connector about 10 to 15 inches from the generator. Check those terminals too.

While you're under the hood, follow the smaller battery positive wire to the under-hood fuse box and be sure that connection is clean and tight. That is a real common source of trouble on all car brands. When using metal tools on that connection, don't let them make contact with any metal part of the car at the same time. Doing so will result in huge sparks. Follow the smaller negative battery wire to where it bolts to the body sheet metal and be sure that connection is tight and not rusty.
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Wednesday, November 25th, 2020 AT 9:04 AM (Merged)
Tiny
TAYLORG165
  • MEMBER
Can you please explain this to me a little simpler? I don t understand cars, haha. What would be the best solution for this?
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Wednesday, November 25th, 2020 AT 9:04 AM (Merged)
Tiny
CARADIODOC
  • EXPERT
You already did the correct first step, but at the wrong time. The defect only shows up once in a while. If any testing is done when the "Battery" light is not on, everything is working so there will be no defect to be found.

Have the charging system tested again, but your mechanic should understand the problem doesn't act up all the time, so the system has to be tested while the warning light is on.

All of the symptoms you described can be caused by a failing generator, but a poor connection in an electrical plug can cause the same thing. Once your mechanic confirms the problem is occurring, it should only take a few voltage tests to narrow this down to a defective generator, (alternator), or a wiring problem.
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Wednesday, November 25th, 2020 AT 9:04 AM (Merged)
Tiny
BMDOUBLE
  • EXPERT
Classic bad ground issue on the Focus. While the engine is running, feel the negative cable near the battery while the headlamps are on bright, A/C on, rear window defrost on, radio on, and any other electrical load is on. More than likely it will be too hot to hold. Add extra 4 gauge wire between the body to engine, body to negative battery.
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Wednesday, November 25th, 2020 AT 9:04 AM (Merged)
Tiny
CARADIODOC
  • EXPERT
Wouldn't that also show up as slow cranking?
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Wednesday, November 25th, 2020 AT 9:04 AM (Merged)

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