The AUSubaru.com.au Forums

I know, should be charging at about 13.5 to 14.2 Volts to charge a battery, but is your alternator really punching this voltage out?

If you could take the effort to measure safely with multi meter or such from your alternator output and report in it would be interesting to see.

My alt died during last weeks or so and it was a slow death until today when sometimes start, others not, leave it while and came good again, then that was it. Alternator read about 4 Volts.

Now , swapped in another alternator to find noisy bearings and only 11.98V, then another that I had on my wagon, clean and tidy and gave no problems for the three week test period. This also only gave out 11.98 volts, so thinkijng battery may be cause, swapped my new one in to then get 12.05 Volts

I propose a theory that unless an alternator is dead we don't often measure charge rate and that maybe it is possible that a lot of our subies are just pushing along for ages with a not so flash alternator output but enough to not kill battery or about 12V.


So... if you have time and means, please measure your output of old MY or L series and report back in with your findings

Ta, Jonno

Keep in mind alternators rarely provide full charge when the engine is idling, see what results you get at 1,500-2,000rpm.

Jordan.

14.2V at idle (drops to 13.9 minimum at idle if I turn everything on and turn everything up). Doesn't struggle at all when driving, no dimming of lights or anything.

Grafton now Jordan ! Yeah, aware of the need for a few revs - no change. Gave up on used idea and went for a reco non exchange unit with a warranty I didn't ask about. At first it gave 12.5V then after a few minutes the charge at all revs , a pleasing 14.5 V - that is factory specs. I hope youse will all grab a chance to check your own volts and keep a survey going - heading into cold weather may help you avert flat battery too

Tested mine last week - 14.4 volts at idle.
Cheers
AP

14.75 without accessories, 14.4 with stereo full, fans full, high beams and driving lights. Well, that was before I smashed it all....

Mines normally up around 14V, you sure the regulators in the alternators you have are in good working order?

On my various subies (L Touring Wag, G2 lib, G3 Lib twin turbo and now 07 H6 Outback), and the other 3 or 4 ive played with I've quite often seen low to mid 13's at idle but always hit just over 14 with a tickle of the throttle.

the one in our rally car got rebuilt weighs half as much as the original and puts 13.5 through an upraded adjustable regulator so it runs constant even with the spot lights on

Firstly to clear up any misconceptions people have about 12 volt systems.
1:A battery simply means a series of interconnected cells in traditional lead acid based cells one thing is constant a single cell fully charged is actually 2.2 volts,therefore a 6 cell 12volt battery is fully charged at 13.2 volts not 12 volts.
2:Required charge rate is acertained to be 1 volt~1.2 volts above nominal full charge to maintain full charge after the application of loads.
3:This therefore means as others have found that the actual required charging rate is 14.2~14.4 volts for a system operating within correct electrical spec.
4:Standard Subaru alternators vary,depending on year from Hitachi LT150 through to LR150 and LR160. LT is early spec with external Regulator,LR means internal regulation on later alternators.
Currently I am adapting an LR170 to my Brumby from a Nissan Maxima V6 it physically bolts up to either an EA81 or EA82 and requires changing the pulley to suit and then making sure the pulley offset is correct,This is thanks to GD and others on USMB and I can now confirm our Aussie spec cars are the same as US spec as far as interchangeability goes,some do have an LR190 as well if you are lucky enough to find one.
Do not forget to get the 2 pin wiring connector from the donor car as you will need it as well,Cheers Coxy.

That is a good explanation coxy, thanks. Openflame, yep, pretty sure the internal reg is not working as well as it should. One reason I asked auto elec and the supplier of the rebuilt one that I fitted that it has NEW reg. Diodes can still go and are new diodes are not part of reco as far as I understand.

Coxy just out of interest Jacko showed me an alternator off an import inline SR20 and it looks sort of similar to your Maxima one - same two spade plug .
The interesting thing is thats its 90a output . I sat it on top of "our" alternator and I reckon it'd almost fall in .
He has one off a turbo and one off an NA SR20 , both are the same .
Its for that R & R rally 16 we saw Saturday with the big lights across the front .

A .

One thing I noticed from some alternator specs is that the Amps rating is not achieved until some pretty high revs - like 5000 ! Just a healthy standard 60A is doing just fine now thanks.