alternator giving me issues...sorrie for long post.

[digitaldrifter91]

well the other day at the local store, come out and my battery is dead, im like crap. so i got it jumped and it was fine, went home and tested the voltage, at idle it was about 11.3 volts.

recently (6mo ago) i checked the charging system and it wasnt really that great, numbers never went up past 12.3 so i knew my alternator was going to go out.

so i buy a new alternator and test the volts at idle...it goes anywhere between 12.6 to 13.30 which is great!!!

when my headlights are on and my stereo thevolts are around 12.9 or so. if i revv the engine it shoots to 13.2 or more

with my cooling fans on and headlights and stereo its about 12.3 if i rev the engine it shoots to about 13.1

with my cooling fans, my headlights, and my stereo and my AC its about 11.5 if i rev the engine it shoots to about 12.3

now i am letting my car sit, and notice the voltage on the battery at rest is around 12.2 which is pretty darn low i think...

so it got me thinking, and i put a new battery. (replacing the 7 year die hard)
...oh btw, there is no contamination or any corrosion on my battery terminals in case you were wondering.

now it runs at just about 14 volts at idle...

yet when everything is on with ac and lights and defog that sucker is still around 11.5 and if i revv it goes up slowly to 12 then barley hitting 13.

im beginning to think that the load is too much for the alternator to handle. i got the old alternator tested and it passed every time, so now im thinking.

what you guys think...most likley need some more amps?

i do have a thread about upgrading the alternator wire size but im not sure if this is the issue....

thank you!

 

[eljefino]

sounds somewhat normal. Alternators put out less juice at idle. That old battery wasn't helping anything but you got that fixed.

That's one reason cop cars have heavy duty batteries: they run all sorts of radios and computers and idle for half an hour sometimes. The battery gets recharged driving down the road.

An in-dash voltmeter sounds like a good investment for you. You could rig up a temporary one to a spare lighter plug.

 

[Papa Bear]

I replace my battery every 6 years.
It has been my experience over many years that the battery will fail in it's 7th year, usually in a parking lot in the middle of Winter at night in a town/city far from home !!
I prefer to change the battery on MY schedule, not fates schedule.
P.B.

 

[Matt_S]

I'd say to go ahead and do the wire upgrade and see where that leaves you. I suspect you'll see an improvement as the small stock wires can cause a voltage deficit, especially if there is any corrosion. That being said, check all the connections for cleanliness, especially body and engine grounds.

 

[RH+G]

A bigger alternator will help (provided all grounds and wirees are in good shape) but your numbers dont sound out of the ordinary.

 

[digitaldrifter91]

..really not out of the ordinary? gee i thought it was pretty low...my accord never goes below 12 wiht a full load, usually stays high.

ill probably do the whole thing, a bigger new alternator and upgrade the power and grounds since im down there.

question, with my new battery, after a night it still sits at 12.08 volts...i thought a battery at rest is about 12.25 at least.

 

[Rickey]

A fully charged 6 cell lead acid battery "should" be 12.6 VDC assuming that the voltmeter is accurate. 2.1 volts per cell is standard for lead acid chemistry. This also assumes a resting period of a few hours after being fully charged or a temporary light load applied after being fully charged. 12.2 vdc resting is too low by a bunch, the vehicle should barely crank on a cold morning with this resting voltage. I am really wondering about your voltmeters accuracy. I suggest a double check of the voltage with another meter against your meter. What amperage is the current alternator? Assuming an accurate voltmeter: with all electrical ascessories turned on, engine running at 2k rpm (fast idle), voltmeter "should" indicate at least 13.0 vdc worst case(14.8 vdc max). These are my figures obtained from experience. With all ascessories turned off you should obtain at least 13.2 and no more than 14.8 vdc at high idle. Most (all?) automotive alternators are calibrated to give more voltage output in cold temperature situations,this should be taken into account also. If the alternator runs extremly hot (spit test) under full electrical load it is too small. Ok I koow you are wondering what a "spit test" is. If you spit on the alternator and the spit just runs away while making a sizzling sound the alternators temperature has to be well in excess of 212F. This condition wil accelerate wearout of the alternator at an exponential rate relative to the actual temperature. Alternate hypothesismore likely ?) The original alternator was bad which destroyed your original battery. This bad (barely functioning) alternator proceded to damage your new battery. Now you have a good alternator and a bad (but new) battery? This is possible I have personaly seen it happen. If both the battery and the alternator get hot after driving 20 miles or so with minimum ascessories on then this would be suspect. Allmost forgot check the wiring: battery and alternator grounds etc. Good luck... Rickey.

[ May 20, 2006, 08:20 AM: Message edited by: Rickey ]

 

[brianl703]

Newer alternator designs often put out more current at idle than older ones did.

The 130 amp Ford 3G alternator puts out 80 amps at idle.

I think the old 75 amp alternator (was it a 2G?) with the external fan was lucky to put out 20 amps at idle.

 

[Gary Allan]

I say that he hasn't come clean on his "stereo" here. I have a feeling that he's got some mega amp'd unit that sucks more current then then a 40foot aquaduct.