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Sneeze
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Discussion Starter #1
On my way to work this morning the battery light kept turning on and then going off. Unsure what the problem would be. I'm thinking 1 of 3 things

1) Bad Battery
2) Bad Alternator
3) Bad Belt

I don't know for sure as the flickering was seemingly random. Anybody have any thoughts?

- Aku
 

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-check the connections first and see if there is any corrosion on the terminals
-check the voltage of the battery w/o running and then while running.

~when does the light go away? when you accelerate? any other probelms ( stalling, staggering, stumbling )
 

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It could be a lot of things. Is the car running alright? Anything else you've noticed?

My first guess would be the actual battery or the alternator. To test the alternator, disconnect the battery while the car is running. If it dies, the alternator is bad (or something else in the charging system). If you have access to a multimeter, test the battery. With the car off, it should be 12.6v and while running it should be in the mid 13's.

If it's not either of those...it could be something dumb like a wire grounding out and completing the circuit for that light. Mine does that with the e-brake light from time to time. I have no idea why, but it doesn't even happen often enough to diagnose it.
 

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Sneeze
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Discussion Starter #4
It has stumbled a bit once or twice. It didn't this morning though. It seems to go away when I start to accelerate a bit but if I just revved the motor up it wouldn't. It also didn't stay on for the same amount of time ever time. It would come on for like 10 seconds then go away.. then on and then off. sometimes i'd just be holding speed and it would go on and off. same with when idleing.
 

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Those are the same symptoms that I was having when my alternator went. I would crusie down the road and it would come on and off, and go away when I accelerated, but nothing when just sitting still. do the steps listed by Pkmgarf. That should tell you what is going wrong. I fried mine because of a loose cable (stupid mechanic replaced the alternator w/o checking the wire and fried the new one in a day)

Hopefully it is something simple.
 

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Hmm....it could be the belt, but you'd be having other problems as well then.

I'd say test the battery/alternator first to see what that tells you.
 

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Sneeze
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Discussion Starter #7
Ok thanks guys. I'll see how its running on the way home from work today and if its still flashing on and off i'll do the alternator/battery tests when I get home.
 

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do it even if you aren't having problems. If you have a loose connection, it could build up on the line and fry the alternator. So even if it isn't giving you any problems, go in and check it out.
 

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Never ever disconnect your battery while its running, sure it may work. but on computer controled systems this creates a shock, or an avalanche load on electrial systems, and you could end up doing more damage then good.
Period. this wasnt even a good idea to diagnose old school generator systems... dont do it. ever on anything. it may work once or twice.
this will create havok on your system, and i could not and would not suggest this on my worst enemy. its bad. [smackbum] [smackbum] [nono] [nono]
 

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Never ever disconnect your battery while its running, sure it may work. but on computer controlled systems this creates a shock, or an avalanche load on electrial systems, and you could end up doing more damage then good.
Period. this wasn't even a good idea to diagnose old school generator systems... dint do it. ever on anything. it may work once or twice.
this will create havok on your system, and i could not and would not suggest this on my worst enemy. its bad. [smackbum] [smackbum] [nono] [nono]
What he said IN SPADES!!! The battery is used as a reference voltage and if you disconnect it the ALT. may go as hi as 16VDC and stay there or it may go all over the map and take out your ECU, high dollar head unit,amps you name it!!!

Rick
 

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Sneeze
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Discussion Starter #11
^ Holy triple post batman

Update:

Didn't have time to test anything last night (looks like it was just as well as i coulda messed something up)

On the way home from work it lit up once and then went away while i was leaving my work parking lot and then it didnt' come back on at all the rest of the night.

This morning however same deal. I did notice 2 things this morning however as I was paying a little more attention.

1) when sitting at a stop light with my foot on the break, when the light came on it felt like the break pedal depressed a little bit more.

2) If i was driving and just holding speed and it came on, i could lift my foot off the gas and shut the light off temporarily, would usually come back on in like 20 seconds or so.
 

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Do the volt meter test at least to see if your battery is good, and if it is getting charged from the alternator. You can take it to Autozone and they will do it for free. Also, try driving with no pull on the battery ( no radio, no ac, no lights) and see if you are still getting the light to pop on.
 

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Did you at least check your battery terminals? I'd check and clean those, then use a voltage tester to make sure that the battery and alt were doing the correct job. A good battery will show just under 12v with the engine off, once you turn the engine on, and the alt is working correctly, the voltage across the battery terminals should read 13-14v.
 

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Sneeze
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Discussion Starter #14
Will do that tonight and report back in the morning.
 

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just take it into a local parts shop lkike shucks, or napa or autozone any place that does free battery checks and ask them to test it accurately and probably free. no worries about guessing about what a problem is.

my shop has a 13 point free battery/charging system check including terminals, corrosion, cables, fluids, alternator output, diodes, exessive starter draw, just to name a few. for free. and it takes all of 5 minutes of time.
 

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Have the same problem month ago. I was able to drive with that for almost two weeks, but when the battery light starts to come more often i take care of it. Spend 45 minutes to get the alternator of, go to AutoZone, and when one guy over there connect it to they tasting machine after 2 two seconds i read on monitor FAILED. Thanks to lifetime warranty they give me new one then i go back home, spend another 30 minutes putting everything back in place and TADA! Problem solved :)
 

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Sneeze
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Discussion Starter #18
Ok so I finally got around to checking my battery yesterday. I think i have an alternator problem.

Used the voltmeter with the car off. 12v. good

Turned the car on and let it get to normal idle. checked again.. 10v. not good.

I'm assuming that means alternator issue just wanna double check before I make the order cuz i'm running out of cash and need to make sure I actually need it first
 

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It's probably the alternator, but the battery may just not be accepting a charge at all. Was it exactly 12v with the car off? It should be 12.6v....
 

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10v running is showing due to the cars voltage draw to the ignition I would change that alternator out asap before you toast the battery which actually looks like its holding a good charge and sustaining the car running..

o_O odd my battery with the car off sits at 12.9 and charges while running at 15.3 volts

Pkmgarf: if the battery isn't accepting a charge it would of failed to start the car within 3-5 starts.. I think the alternator is giving off a residual charge keeping the battery at bare minimum
 
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