GTO2

how to tell if alternator is not functioning as it suppose to, other than flat battery?
If voltage alone hits around 14V, battery is new, no other electrical load, yet battery seemed weak, could I check how much charging (Ampere) goes into the battery in relation with rpm; example what is the charging Ampere at 1krpm, 2krpm and so on?

thanks.

JRR

iTrader: (19)

well the battery should only be at 14v or around when the car is on and charging. if the car is running and yur getting less than like 13.5 volts then you may have a dieing alternator. check the power coming out of the alternator with a volt meter with the car on. that will tell you a lot

paul_nickolas

I have always had a difficult time trying to test with no load, so maybe with no load it should be above 13? Just make sure you turn off lights, HVAC, stereo, shut your door, and look for anything else that could be drawing electricity. Radar detector may or may not have any impact.

Earlier posters say 13.5 or less is a warning sign - and I would agree with that. Especially if you have tested your voltage with all your accessories off.

My general rule of thumb is that if the interior lights get brighter as you rev your engine, you may want to check your alternator. My 2005 ES started having a slight difference when revving, once I reached about 90K on the engine. Not significant though, and battery remains charged.

(I made some slight edits to my post after re-reading after posting.)

zebra4

Unless you have an underdrive pulley, which will also cause this. On and charging output should be 14.6 (mine runs at 14, never had an issue), and 12.6 when car is off with all accessories off.

GTO2

OK,
measured at 1krpm idle, it is 14.4V and current is 1-1.5A.
I am yet to measure how much the current will be on 2krpm and so on.
A diagram i found shows that i should expect a higher current reading as rpm increases to confirm if the alternator is functioning well.

not exactly the same alternator, but the curve should be quite similar perhaps with different readout.
about 20A+ on 2krpm..

source:moparstyle

mci2727

iTrader: (12)

Man you can take your car to most any auto parts store and they can hook-up and check both your battery and alternator, on the car.
That's what I do when I think I've got an issue.

Why do you think you may have a bad alternator?
What's goin' on with the car?

GTO2

the workshop said the alternator is fine, voltage measurement concurred that too.
Thing is even the battery is new, i always get the battery indicator light up every time i turn key to on and it stays on until engine cranked up.
I run into this before on my old battery, only 1 year old and it ended up dead.
So i would normally think there is something wrong with the charging, slow or anything, other than ECU or some other sensor problem.
Would alternator with dying brushes give this issue? i'm over 120k km mileage.