Battery Light Just Came ON

[beaudeen]

G'day....
Just about to head out to the parents place
350 miles north...battery light just came on..car started
normal the last 4 stops today..just metered the battery
and it was 11.80v with engine off but starts normally..3 of
the cells were low...topped them up a few years ago when
had difficulty starting her up 2 winters ago..battery is 7 plus
years old...lol...BUT
here's what I have with engine running.
800 rpm
no assy on....14.2v
assy on lights/defrost/a/c/fog lights....12.4v

1500 rpm
assy on....14.2v
assy off....14.4v

Question is...is my alt over charging ..??
is my battery pooched...??
Alt is original with 250km(150k miles)

Stores close in an hour and a half
I've used the search, but most seem to be on under charging.

Help appreciated...thanx

 

[kevinspann]

Both most likely. Change the battery first.

 

[beaudeen]

Just went for a 1/2 hour drive on the hwy
at 60 mph..battery light on the whole time.
Checked battery voltage when I got home..13.2v
Disconnected battery while engine running..still runs fine
Battery light still on..alt voltage is at 14.25v..is this too high..?? IIRC
it should be 13.8ish...is this what it triggering the battery light..??
The battery light should have gone out when it charged up
to 13.2 volts..no..?? I'll leave the charger on it for the night
and check the draw on start-up to see if the battery is pooched.

 

[SHOZ123]

The proper running voltage should be 14.4 V. It sounds like the battery is dragging down the alternator. How are you reading the alternator voltage?

 

[beaudeen]

Positive lead of the battery removed..metered with the
engine running..I would think that would be the alt output
voltage right..?

 

[Phoenix]

The batt light comes on cause it has issues with the alt , or the wires.

Before you drain the batt I suggest you check it out.

 

[beaudeen]

I read a few of your post stating it's the alt 99% of the time
when the battery light comes on..I'll take it to my guy in the
morning to rebuild...He has one in stock for $130, but i'd prefer
him to rebuild mine...
So...my battery is fine for the time being then...if it holds
a good charge right. I'll replace it before the winter.

 

[TimboSHO]

Check your power wire from the alternator. I've just had one of those come apart. Just pull on it a bit and see if the eyelet comes off. I also had a SHO that had sat for awhile that was overcharging, it ended up being the alternator.

 

[beaudeen]

Charged battery over night..13.2v

engine running......14.90v

battery voltage drop on
warm engine start....10.98v
then back up to 14.9v
Battery light is now off..i cleaned all the alt
connections and the main power connection is
clean and solid..
Should I be good to go...or...is it going to
fail on me on my trip...not feeling too confident..
Going for a 15 minute drive to see how things pan out.

 

[Phoenix]

Charged battery over night..13.2v

engine running......14.90v

battery voltage drop on
warm engine start....10.98v
then back up to 14.9v
Battery light is now off..i cleaned all the alt
connections and the main power connection is
clean and solid..
Should I be good to go...or...is it going to
fail on me on my trip...not feeling too confident..
Going for a 15 minute drive to see how things pan out.

Maybe cause its overcharging , it shouldnt be more then 14,4.

Maybe it was your wire , tripping the light.

Depends on where is your destination , for me , if it was more then a 50 mile trip , I wouldnt take the risk - but that depends on the person.

 

[SHOZ123]

14.9v means a bad voltage regulator. It will cook the battery after a while. As the battery cooks the acid gets stronger due to the water being driven off through electrolysis. This shortens the life of the battery quickly and also shows a higher open circuit voltage due to a higher specific gravity of the electrolyte, it also raises the temperature of the battery which looses more water through evaporation Capacity is way down though.

 

[beaudeen]

Thanks for the reply guys..I hear both of you
loud and clear..!!!

20 minute test drive ..no issues...no light

The over charging point makes total sense as to why
I had to top up the electrolyte in the front 3 cells.

6 hour drive up to Sudbury will probably worsen matters
so off to my rebuild guy...Thanks again for the help..!!!

 

[SHOZ123]

If only three of the cells were low on water then the battery is bad too. If it was just the alternator then all 6 cells would be low with the inside ones the lowest due to internal heat.

A bad battery can cause a bad alternator by over stressing it causing it to put out too much load. Usually this is seen by low voltage running voltage in an otherwise good alternator. Thought the alternator will not stay good for long.

A bad alternator can cook a battery and cause internal cell failure because of too much current and the resulting heat.

 

[beaudeen]

So...what should I do now..??
Start with a new battery then..?? It is almost 8 years new..

Am in the process of removing the alt..elect disconnected
2 bolts out and the tensioner is backed off, but no slack
in the belt yet..how many bolts hold this thing on..??

The rebuild guy asked what condition the battery
was in..he says that these numbers seem fine to him, but
point to a bad battery..??

 

[SHOZ123]

I would replace both. Take the belt completely off.

 

[beaudeen]

OK..got her off..forgot to loosen the tensioner
pulley bolt..and missed the 12mm bolt on the rear
of the alt...
Replace both you say...OUCH,,,$$$
$130 for the rebuild and another $100 for a battery.
Oh well...both have seen better days...alt is original Motorcraft.

He wants to bench check it, but rebuild wouldn't hurt..best elect
shop in town.
Thanks again...it's friggin pouring rain now..trip can be postponed..

 

[beaudeen]

All done..
Battery tested ..volts drop like a rock under load.
It was hanging on by the skin of her teeth...odd thing
was, I never had a problem starting..turned over just fine

Alternator tested BAD...over charging 15 plus volts.
The shop did a really nice job..looks and smells like a
brand new unit...good for another 16 years..lol

Thanks again for your help guys...much appreciated..!!!

 

[SHO_ROLLER_2]

I know I'm a little late, but why rebuild it for $130 when you can get one with a lifetime warranty for $180?

I just went and picked up alt. number two. The first one went out after two and a half years, but hey, went in and they handed me a new one.

 

[beaudeen]

Just got back from my 600 mile trouble free trip.
The reason I rebuilt my original Motorcraft alt was
It's built better than the Chinese junk you get at the
big parts stores. Also, why not support your local shops
rather than sourcing out jobs to China.