Ford Focus Battery Light issue - Help

[abbasdr]

Hi,
I just recently bought a used Ford Focus 2006 sedan.

I started the car after 1 day of it being idle and it started immediately without any issues. The dash lights went out but, the Battery light kept on very faintly lit, not like it goes on when you turn the switch on. I kept the car running thinking that it might need charge or something, but, it remained on (dim). When I switched the car off the it is still on (again very very dim).

I checked online and some suggested that the diod for the alternate are going bad, and someone said that ground issue or something. I checked the battery terminals they seem clean (a bit greasy but no corrosive white stuff) and are really secure to the points.

I have zero knowledge of car repairs and stuff :

I am in school and have zero money to spare for repairs :\ and just want something that can get me through the winter (car used just around city, no highways) and uptill next May-June or so. So keeping these two things in mind what should be done, and is it safe to drive around? Off course if the battery light comes on full glow, that would probably mean the alternator is dead or something, then has to be replaced. But until then ...


Thanks


(Never knew anandtech had car section Kool!!!)

 

[LTC8K6]

That typically means an alternator problem.

If you have an auto zone or advance auto near you, they will test you battery and charging system for free.

If you can use a voltmeter, you can measure the battery voltage with the car running and get back to us.

 

[abbasdr]

Thanks for the reply. Had it checked, they said that the battery is the culprit. The charging was fine.
When I asked them about the light being dim on even when the car is shut off, they had no clue. Said they have never had seen/heard that one before...... Hmmmm!
Not sure what to do. If the battery is replaced and still the light stays there, what is the point. Also I am thinking that to continue with this battery until it dies out, and that most probably happens after car being idle for a long time. But can the battery die all of a sudden even if the car is running around?

 

[LTC8K6]

I would get a new battery anyway. It's relatively cheap insurance, especially if your battery is several years old.

There's no telling when the battery may quit, but it won't cause the car to stop running. It just won't start one day.

Could be the wiring on the alternator. Take a good look at the wiring and particularly the connections at the alternator. See if they are loose. You may need to unplug a connector to get a good look at the condition of the contacts.

One quick check would be to wiggle it and see if that battery light goes out. Maybe get a friend to help.

A few online threads suggested the pigtail at the alternator as a possible problem.

 

[phucheneh]

Batteries usually don't cause the light to come on. The light is basically an indicator of a lack of charging voltage. The caveat is that, yes, a bad battery CAN cause a lack of charging output...but it's somewhat uncommon.

Usually a bad battery will be functionally fine if it doesn't have much strain put on it. As in, you will see normal voltages, and the car will keep running indefinitely. But its reserve will become exhausted very quickly; even after running for a long time, or significant time on a battery charger, symptoms of a dead battery will appear quickly (slow cranking, very few starts before the battery is drained, ect).

But the alternator will keep trying to charge it. Which means charging output well above battery voltage...which means no battery light.

Still, I generally say worry about the battery first. You can vindicate or condemn it independent of the alternator; the inverse has those rare cases where you could possibly replace an alternator whose symptoms are being caused by the batt. Don't wanna do that.

Take the battery to whatever parts store you trust the most, and let them charge and test it. Then take your fully charged (possibly new) battery, reinstall it, and check the alternator output. If you find less than about 13.8v while the car is running, you need to check it at the alternator post. Testing at the battery is okay for declaring the charging system good. But if there's a problem at the batt, you have not pinpointed the problem. Proceed to testing at the alternator (positive probe on big post, neg on alternator casing).

Same as battery voltage: alt is putting out nothing. Possible bad alternator (usually the internal voltage regulator), but also very possibly an issue with the input wires for the alternator- there should be two small wires, and they should both have battery voltage with the ignition on. Lack of power at either can result in the alternator doing nothing.

No voltage: Typically a blown fuse. I believe your car has an alternator fuse in the engine fusebox. Unline most cars, the alternator cable (fat red wire) does not run straight to the battery. It and the battery both connect directly to the fusebox. The alt fuse will be 100a or higher; you may need to check your owners manual to find it. Ford doesn't like put labels under the fusebox cover, just numbers.

Normal charging voltage (but charging voltage at battery is low): excessive resistance in a cable.

 

[LTC8K6]

When I switched the car off the it is still on (again very very dim).

I have heard that if the light stays on with the key off, it could be a diode in the alternator.

 

[phucheneh]

I thought he was talking about the batt light with key on, engine off, and just didn't bother saying '...that's normal.'

On all the time, when everything else is off? That would be strange. A bad diode might make sense, but I don't think the typical alternator diodes one would think of (in the rectifier bridge) are in place there.

It's too late for me to think clearly about that...all I can say is that I just can't ever recall seeing that on a car. If I did, I didn't notice it and just went about fixing the charging system in my typical fashion.

I would wanna see a wiring diagram for his car to refresh my memory. I'll pull one up at work tomorrow if I think of it.

I'm reminded of the old GM trucks (might only be the military ones; not sure if the civvies with Detroits in them were the same) that would quit supplying voltage to the alternator if the batt light burned out. What a paradox. :awe:

 

[Danimal1209]

Had that light on in my eclipse for about 5 months and then the alternator died. Changing battery didn't help. After replacing the alternator the light went away.

 

[pcgeek11]

I have heard that if the light stays on with the key off, it could be a diode in the alternator.

Yes this. It is one of the Positive Diodes in the alternator rectifier circuit.

 

[abbasdr]

Thanks guys for the feedback.
O the light stays on even when I shut it off and remove the key (faint, faint) ...
The repair shop guy said the same thing That he has not heard of that one before.
Changing battery does make sense as it is gonna be winter soon, snow and all, and I read that battery output is halved at subzero temps.
As for the diodes, would I have to get the alternator changed too? O i so didn't wanted to spend any monies on the car

 

[LTC8K6]

Thanks guys for the feedback.
O the light stays on even when I shut it off and remove the key (faint, faint) ...
The repair shop guy said the same thing That he has not heard of that one before.
Changing battery does make sense as it is gonna be winter soon, snow and all, and I read that battery output is halved at subzero temps.
As for the diodes, would I have to get the alternator changed too? O i so didn't wanted to spend any monies on the car

Well, if it is an alternator diode, your battery is being drained even with the key off, I think. It could cause you to have a dead battery if the car sits for a couple of days.

I would wonder why the testing didn't catch the bad alternator diode?

 

[abbasdr]

I will take it to another repair guy and see what they say, just been busy with school.
I contacted someone else and they said it could be an earth issue? Hmm

 

[Zenmervolt]

I will take it to another repair guy and see what they say, just been busy with school.
I contacted someone else and they said it could be an earth issue? Hmm

A bad ground could make the light come on when the car is running, but it would NOT cause the light to stay on even when the key is out.

It really looks like the most likely culprit here is the rectifier circuit in the alternator. That's generally not a serviceable item and you'd need to replace the entire alternator. I recommend an OEM unit and NOT a "lifetime warranty" rebuilt part from AutoZone (or similar discount parts store). The cheap rebuilds tend to work for a while, but in my experience they have a shorter service life than a new OEM unit.

ZV

 

[pcgeek11]

The Diode "can" be replaced if you are handy with tools and a soldering iron. I've done it before, but I work in electronics daily. $1.00 for a diode or 200 for an alternator...

You will need a DVM to determine which diode is shorted. You may be able to locate a complete diode bridge assembly.

 

[abbasdr]

Thanks guys for the info. I am useless with repairs probably cannot fix a flash light if I had to '
Anyways, here is an update... I went to one repair shop and they checked everything, switched battery with a one that they had light remained on, no change.
Checked Alternator, everything fine.
Then they tell me that I should check with a car electric repair shop.
Anyways, went to one of the best (here), they went over everything again, checked battery under load etc etc...
They told me that Alternator is charging fine, the battery is accepting the charge and everything looks good. No issues. When I asked them that it can be a diode in the alternator, they said it would be difficult to point it out as they will have to take it out and it doesn't seem like there is an issue with it. And as for the light it might be something within the instrument cluster, and that would have to be scanned by Ford folks. They did say to me if it is not draining battery (which it is not), I should just let it run as such.
Ford repair is gonna be steep and probably not worth as the car is cheap.
Kinda confuse as what to do now I am thinking about just letting it run like that until (I hope not) it stalls........

 

[LTC8K6]

Hard to believe a competent mechanic can't test for a bad diode.

 

[pcgeek11]

Hard to believe a competent mechanic can't test for a bad diode.

The key word is Competent. He was not.

A shorted positive diode usually doesn't show up as the alternator will and does charge the battery when the engine is running. If you let it sit for a while it will discharge the battery.

 

[abbasdr]

Thanks guys for your input.
REALLY really frustrating, I mean I've been to 3 repair shops, they just shrug me off as if I'm an idiot. And tell me nothing is wrong and start moving to more expensive repairs without any rationale. They charge me for their time even though they don't even reach a conclusive diagnosis, even when told.

I tried talking to them that it can be a diode... and they said they probably cannot check for it. Car repair folks are just a pain in the back Haven't had to deal with them as had a new car for the past 7 years and now as I am back to school and money is tight I am at their mercy......

Just a quick question, if the light doesn't drain the battery and the car starts fine, do you think that the alternator can last for sometime without changing it. I know if the alternator goes I will be stuck on the road and probably that might kill the battery too (not sure though). OR I am thinking about talking to someone to just swap the alternator without going into "Diagnostics"

 

[LTC8K6]

Thanks guys for your input.
REALLY really frustrating, I mean I've been to 3 repair shops, they just shrug me off as if I'm an idiot. And tell me nothing is wrong and start moving to more expensive repairs without any rationale. They charge me for their time even though they don't even reach a conclusive diagnosis, even when told.

I tried talking to them that it can be a diode... and they said they probably cannot check for it. Car repair folks are just a pain in the back Haven't had to deal with them as had a new car for the past 7 years and now as I am back to school and money is tight I am at their mercy......

Just a quick question, if the light doesn't drain the battery and the car starts fine, do you think that the alternator can last for sometime without changing it. I know if the alternator goes I will be stuck on the road and probably that might kill the battery too (not sure though). OR I am thinking about talking to someone to just swap the alternator without going into "Diagnostics"

It's certainly draining the battery. The question is how quickly.

It may be fine if you drive it every day.

It may not start that one time you let it sit for a couple of days.

If you are not going to fix it, then I suggest you be prepared to deal with a dead battery, just in case.