GC8 MY2000 UK turbo.

I've noticed that the dash clock flickers slightly and also the front sidelights (ebay white LED's). Suspecting that the alternator might be faulty I checked the battery with my multimeter:
12.2 v when not running, rising to 14.4 when running with headlights on and revving the engine to 2000 rpm. The reading when not running is too low but does the latter indicate that the alternator is ok?

Thanks

 

14.4v output from the alternator given the charge held by your battery seems fine.

You can use this as a guide to the determine the state of charge in the battery

 

Generator info from a "Classic" Model Workshop Manual........

 

Thanks Don, appreciate it.

 

The regulated voltage varies between 14.1 & 14.8.

Please explain to me how the regulator knows: -
1) how to regulated 14.8V
2) how to regulate at 14.1V

Some background information.
I think 14.8V will boil a sealed lead acid battery.

Our 2000, 2.5 the float on our Subaru's battery Yuasa battery
has sunk almost out of sight.
Yuasa tell me I can't get the top off to top it up.

My certificated meter showed 12.5V across the posts before starting
14.8V immediately after starting with the engine ticking over..
Around 26 Amp along the battery cable after say 10 mins.

After a run, the meter showed 14V with the engine ticking over.

Could 14.8V be a correct charge voltage for a flattish, suspect
battery on start-up please?

:

 

The alternator monitors the battery's output load and adjusts accordingly both voltage and current. (known as a smart charger)
Only if the alternator current output is not regulated correctly.

Will be a sealed for life battery.
When you say "the float on our Subaru's Yuasa battery has sunk almost out of sight".
Are you refering to the green/black telltale? green for good; black for recharge?
A reading of 12.5v is about 90% charged depending upon temperature at the time and if the battery has lost it surface charge from previous charging.
It's CCA reading would tell you it's condition and whether it is suffering from sulphation.

To charge a 6 cell 12v battery you need to supply a voltage greater than 12v usually somewhere starting between 2.35v/cell (14.1v) and 2.45v/cell (14.7v) depending upon the charging method and the battery's temperature.
https://www.power-sonic.com/blog/how...-acid-battery/
The more crucial question is what is the battery's capacity/condition when charged or it's CCA (cold cranking amps) value.
The typical Yuasa battery for a Subaru is the Silver YBX5005 12v 65Ah with a CCA of 580A when new and fully charged.

So in answer to
My answer would be yes and to get yourself something like a Ctek battery charger and conditioner.

 

Thanks Don, you really know your stuff don't you.
Do you train auto electricians by any chance?

I am very sorry I'm so late responding.

 

Google assistant and Alexa will give You the same answers

 

jdmSti2006;12131597]Google assistant and Alexa will give You the same answers

Thanks Jd.

How do I change the background around your words,
the words that are in violet above please

 

I have an MXS 5.0 Don.
And an external connector.
But I have to admit to being too dumb
to disconnect before I drive off

The alternator in question is a simple 3 wire one.
Are there Smart 3 wire alternators please?

 

What is it you are trying to say???
You have to switch off and disconnect the Ctek before driving off, why would you leave it attached??
What alternator /car model are we talking about??

 

2000 2.5 Legacy..

 

What do you mean by "3 wire" - One on the stud and two in the plug socket? or 3 in the plug socket (total 4 wire)??

If it's 2 in the plug (feedback and charge circuit light on dash), then it's just voltage regulated.

If it's three in the plug socket (feedback, charge circuit light on dash and ECU link) then it's a smart alternator regulating both voltage and load.

 

Thanks Don.

I mean 2 in the plug (feedback and charge circuit light on dash), and 1 under the nut.

If it's a dumb alternator, how come I get
14.8v at start-up, which falls to 14v after a run please?

I can't remember meeting a dumb alternator
that varies the charging voltage.

 

https://smartercharger.com/blogs/new...ernator-enough
https://www.autoelectro.co.uk/alternators

 

Thanks Don, Interesting.

 

Have you got a clamp ammeter Nick?
How many volts at tick over with headlights on.
How many volts at your battery in the morning
before you start please?
How long since you last replaced & then tighten
your fan belt please?

How old is your car please?

 

https://axleaddict.com/auto-repair/A...Regulator-Test

 

My word, that a very nice reference Don, thanks.

There seems to be a lot of white space.
Are there a lot of pictures + missing please?