Battery Light on my F-150

[Capt Steve]

I was driving home from San Diego on Monday and got the red battery warning light - it looks like a little red battery on the dash display. The voltage was normal but 80 miles from nowhere in the Arizona desert it was a tad disconcerting. I stopped and checked the battery, not hot or even warm, connections tight with no visible corrosion. The owners manual says absolutely nothing about this so I have that going for me...can't be confused by any misprints in the manual. (o;

Knowing the battery was 5 years, I old figured it was time to replace. I drove on and if I put in the clutch and dropped the rpms to idle the light immediately went off. Resume normal driving and after a few minutes it was back on. This cycle repeated it self all the way home to Tucson. I pulled the battery and the hydrometer showed it pretty well gone. I dropped a new one in and the damned light stays on all the time. I have full electrical function and good voltage. The Ford dealer says maybe it will go off on its own, if not, bring it in to have the electrical system checked ($Cha Ching$!).

Any ideas guys? I am going on vacation for a couple of weeks so will probably just let it sit in the garage until I get back.

 

[Crazy K38]

have the alternator and solinoid checked immediatly it sounds like the alternator is going out

 

[gunsmith11]

check the alternator and the connections

 

[GatorFarmer]

You could put a piece of tape over the light. Problem fixed.

Alternately, go to an auto parts store, I think one chain - Auto Zone? - will do a free diagnostic to tell you lights coming on mean. Failing that, somewhere there might know.

But yeah, probably the alternator.

 

[2Loud4You]

have the alternator and solinoid checked immediatly it sounds like the alternator is going out

Bingo! The battery light is kind of a misnomer. It really means you're not charging vs. something wrong with your battery but the engineers knew the a battery pic was the smartest to go with because people would hopefully go get it checked.

 

[zercool]

Bingo! The battery light is kind of a misnomer. It really means you're not charging vs. something wrong with your battery but the engineers knew the a battery pic was the smartest to go with because people would hopefully go get it checked.

Well, that's part of it - but have you ever tried to make a line drawing of an alternator that's 3/8" high and any schmoe with a driver's license would recognize?

There's a reason they just went to one red light that says 'CHECK ENGINE'.

 

[windjammer]

Capt Steve......I had a 98 Crown Vic. the Battery light came on. I had the Battery checked at Auto Zone. It was 5 years old. They said it had a week cell. I replaced it.

The darn light still came on. Sometime it would stay on, the next time, it might go out after running 15 minutes, then come on again.

I took it to the Ford dealer. They tested everything and couldn't find anything wrong.

I drove it for another 5 years with the light coming on and off.......I traded it off a year ago and never found out about that light. It always bothered me. Never found the answer. Bothered me every time I took a trip.

 

[Landpimp]

most likely the alt, but I only know Toyota's

 

[Spotteddog]

Voltage regulator and/or connections @ alternator.
Also, check engine/body grounds.
What year/mileage?

 

[2Loud4You]

Well, that's part of it - but have you ever tried to make a line drawing of an alternator that's 3/8" high and any schmoe with a driver's license would recognize?

There's a reason they just went to one red light that says 'CHECK ENGINE'.

Actually the Check Engine light is Amber while your Battery and Brake warning lights are Red. Red means it's a more serious problem that needs to be addressed immediately while Amber indicates less severity BUT I know what you were getting at.

 

[Capt Steve]

It is a 1998, 4.2 liter V6, 5 speed with 96,000 miles. I spoke to the local repair shop and he said it sounds like it is either over/undercharging or a bad warning light. We will find out on Monday. In the meantime I drive the golf cart or the brides Solara Coupe. I'll let you know what we find on Monday. Thanks to one and all for your input. It's nice to know I can count on this bunch for answers.

I do kinda of miss the political forum though. Seems like a lot of the most entertaining folks to be found there have gone elsewhere. Ironically one of the most frequent complaints they had was that some folks only posted there, and now they are gone. Hmmm? Maybe the spaceship that got Jimmy Hoffa has been cruising the forum??? Tin foil hats anyone? (o;

 

[windjammer]

It is a 1998, 4.2 liter V6, 5 speed with 96,000 miles. I spoke to the local repair shop and he said it sounds like it is either over/undercharging or a bad warning light. We will find out on Monday. In the meantime I drive the golf cart or the brides Solara Coupe. I'll let you know what we find on Monday. Thanks to one and all for your input. It's nice to know I can count on this bunch for answers.

Although I no longer have my '98 Crown Vic. I always wondered about that battery light staying on 50% of the time.....No one could find anything wrong, including the dealer.

 

[MK]

I don't know if this is the case, but I remember cases where the failure
of one of the diodes in the alternator can cause the light to stay on.
In this case, I think the alternator still works to some degree, but not to
full capacity. Most of the auto zones, etc have testers that can check alternators.
I dunno if they can sense a single failed diode, but might be worth a check.
Also, I kind of doubt this is the problem, but make sure the belt is not slipping or
loose.

 

[Crazy K38]

if it were loose it would squeal like a live pig on a spit though, and the only thing they test for is a short, so if it is a single diode I think it would pick it up though, but thanks I had forgotten about that

 

[Spotteddog]

The diode trio short/open should have been picked up during the testing? Question. Was the alternator "bench tested", or while actually on the vehicle? Also, if done on an oscilloscope the sine wave form of the trio can be be displayed to look for raggy wave forms. Is this a model that runs an "integral" or "stand alone" voltage regulator? If a stand alone (as I mentioned earlier) it's ground quality is critical. Last question, does the relative brightness of the battery indicator lamp go up and down with "loads" (lights, heater motor, etc.) will the battery lights output be affected by dimming the dash lighting?

 

[Capt Steve]

I'm having it tested on Monday at the local auto repair shop (not the dealer). The red battery light has the same brightness regardless of the load. Don't know off the top of my head if there is a stand alone regulator or not.

 

[Capt Steve]

It's fixed!

Well they checked the charging system this morning and while the alternator was charging its output was marginal. I told them to go ahead and replace the alternator. Total came to $254 with $187 of that the alternator the rest was labor and tax. I expect that will be the last alternator I buy for this truck given that the first one lasted 11 years. Thanks for all of the help.

 

[2Loud4You]

Just what I expected.

 

[Crazy K38]

that is what I figured, glad you got it fixed