alternator on its way out?

[ToothbrushMan]

evening people.
just need some pointers on these battery and alternator readings.
alternator is 5 years old.
battery is 4 months old.
battery at rest 12.22v
battery on idle no load 13.93v
battery on idle with load 12.3v quickly falling and then hovering at about 11.85v


is that last reading cause to suspect the alternator is on its way out. shouldnt this voltage reading rise not fall?

when revved under load it does rise to 13.2v

[andyiley]

Alternator with no load should be around 14.5 volts.

Measure it at the battery wiring (not terminals) with the positive disconnected from the battery.

[Steve_D]

Depending on the drive ratio the alternator is often not charging at idle so you should be testing at about 1500rpm.

See what you get then.
I'm betting it will be OK.

Steve

[andyiley]

Good point, yes it can be a "fast idle" before there is full charge.

[Doctor Volt]

andyiley

671 posts

35 months

[report]
[news]
09:39 quote quote all
Alternator with no load should be around 14.5 volts.

• ****Measure it at the battery wiring (not terminals) with the positive disconnected from the battery.******

Do Not Under Any Circumstances Disconnect The Battery
That one above is one of the funniest posts I have read Here

[Doctor Volt]

ToothbrushMan, those readings you posted look good to me

What problems are you experiencing?

[trickywoo]

A charged battery in good condition should be 12.5 / 12.6 V static. Your 12.2 sounds low to me.

Charging should be 14 to 14.5 V.

[andyiley]

Doctor Volt.

So how do you suggest being able to absolutely prove that a stuffed battery is not dragging the voltage down?