Well if anyone remembers I had an alternator failure, ended up
replacing the alternator and battery. Well at idle when I applied the
brake pedal, my interior dash lights, headlights, etc would dim. If
the blower is on high it will slow. Sometimes they recovered and
sometimes they did not and would stay dim until I released the brakes.
I said the heck with it and swapped out the new alternator for another
unit (Hitachi). The lights are still dimming at idle. And like I said
sometimes the alternator will recover and other times it will not.

I can understand if there is a very heavy load on the alternator, but
even if I have the interior lights on only, apply the brakes, the
interior lights will dim.

I took it to a good mech he said everything was fine and that the
voltage drop is normal at idle. This is the first car that I have had,
that when at idle the alternator has trouble putting out enough power.


Anyone have more ideas?

Thanks,
Matt
1996 Subaru Outback wagon

fly1747 (AT) aol (DOT) com wrote:

Did someone own the car before you and perhaps put an underdrive pulley
on it?(smaller than stock crank pulley) That would reduce alt. output
somewhat.

That's all I got. Other than refreshing all the ground connections as
suggested earlier.

Carl


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to reply, change ( .not) to ( .net)

Might want to check the battery for a bad cell. Check all battery
grounds.

fly1747 (AT) aol (DOT) com writes:
I agree with the mechanic. Some dimming at idle with the increase of
load on the engine and brake lights with the brake pedal, that does
slow the alternator a bit. I only notice this when my fan is running
on 3 or 4 though.

Dunno if that helps.

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Todd H.
2001 Legacy Outback Wagon, 2.5L H-4
Chicago, Illinois USA

Not a question of alternator. Its a question of post-voltage regulator amps
to power 4 lights or 9 lights.

Think about it as a flashlight battery (the cicuit the lights and switches
that turn the lights on and off). There is X amout of amps doing Y amount
of light power. If you take X amount and divide it by Y + Z light power,
what happens if it's evenly distributed?

Less power to the bulb and a dimmer light. On the headlights, it's
noticable.

If the regulator is not letting more power through, it could be a design
flaw, or a design to keep the lights from using too much juice when you need
it elsewhere.

Yeah, it's a little worrying the first time you notice. But it is not
unusual for a Scoob.

Uh....Carl.....smaller makes it spin FASTER..........it would put out
MORE..not less.......

Eric Cartman wrote:

Uh,,,,,Eric....I said CRANK (not alt.)pulley - decreased circumference
at the SAME engine RPM = less distance traveled.

I think???

whatever - there are folks who swap out crank (and, indeed, access.)
pulleys for lighter - and sometimes smaller CRANK, pulleys. Redused
rotating mass and quicker 'spin-up' of the engine. Like a lighter
flywheel sorta.

lol!

Carl


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"Carl 1 Lucky Texan" <alckytxn (AT) swbell (DOT) not> wrote


Good thing they dont know an alternator eats between 3 and 5 hp....they
might get rid of that too for more power...

Eric Cartman wrote:

Trust me, they do.

So this is something that I should not worry about?

Thanks for all the help.

Matt