Alternator bad? Voltage regulator maybe?

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Car wouldn't start (an old '92 Subaru Legacy L wagon).  Battery is about
3 years old and the car started a week ago.  However, today it just
cranked like one turn and died.  I can hear the relay click as I turn
the key but the engine doesn't budge.  I also noticed the electric seat
belt moved slowly.

I popped the hood, jumped started from my other car, and with a
voltmeter measured across the battery.  It measured 12.5V.  As I recall,
each cell in a new battery should be 2.2 volts and there are 6 cells so
a new battery should measure 13.2 volts, so 12.5V isn't bad for a
middle-aged battery.  However, I expected the voltage to be higher while
the car was running due to the output from the alternator.  The voltage
also did not fluctuate when I revved the engine.  It dropped a volt when
I turned on the headlights.  So it looks like the alternator is bad.
While 16 years old, mileage is only 135K so, on average, the 2
alternators have lasted only about 67K which seems a bit short-lived
(actually the first one probably lasted 105K and the 2nd died after
another 30K).

I had to replace this alternator about 4 years ago.  The prior run
burned up.  Its bearing went bad and it heated up so you could smell the
varnish on the windings within a few blocks of driving from cold.  It
was a rebuilt and is now out of warranty.  I got it for around $80.  The
salvage place doesn't have another alternator (except for a
retail-priced new one).  I can get one for $118 at PepBoys with a
lifetime warranty; however, I'm wondering if just the voltage regulator
is shot.  I can't see what the module is on the outside so maybe the
regulator is inside.  If inside, I'm not dismantling it to replace that
module.  I suspect if it is inside that it'll be riveted and positioned
where it won't be easy to get out to replace it, assuming that just the
regulator can be purchased and is much cheaper.  If the voltage doesn't
get above what the battery alone will provide, is it even a voltage
regulator problem?

I can't find my battery charger so I'll call a buddy to drop by with
his.  I need to charge the battery so I can get to PepBoys to have them
do an alternator test and have enough juice in the battery to start it
again to get the old Subie back home.


What should be the voltage across the battery while the car is running
and with a working alternator?  I thought it was 14.4V.  It would have
to be higher than the 13.2V for a new battery.

Is the voltage regulator inside or outside?

How trustworthy are these parts shop alternator testers?

Suggestions on how to go cheap on the alternator replacement?  The
1-year salvaged rebuilt alternator lasted 4 years.  Considering it was a
third the price, another 4 years is just fine with me.  

Re: Alternator bad? Voltage regulator maybe?


This alternator has an IR.  Problem probably is the alternator has lost a
diode.  Not worth tinkering with if you haven't rebuilt a few.  You can
use a much newer alternator if willing to change the wiring plug.
Thinking 1994 was the year the plug changed.  

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Re: Alternator bad? Voltage regulator maybe?


"johninKY" wrote in

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Sorry, but my primary career has been in computers.  IR, to me, means
InfraRed, as in the light spectrum used by communication
transmitters/receivers.  Maybe IR means Internal Regulator?

I just looked again at the alternator in my car and see nothing that is
accessible from the outside to let me swap out a regulator module.  I
couldn't even find a tag that listed the amp rating.  Any idea how many
amps the replacement alternator should supply?  I think it is 70 or
maybe 80 amps.  This car does have air conditioning (the compressor is
still in place but the system sprung a leak after a recharge and hasn't
worked in over 10 years - I'd like to remove the compressor to remove
any drag, if there was any since it is never turned on, but don't see
how to put a pulley there for the belt).  Of the few places that
mentioned a rating, I usually see 70A units although 50A and 90A were
also mentioned.

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Never rebuilt an alternator.  My guess, based on the assumption that bad
luck is likely, is that I would open it up and find I had to dismantle
everything to get at a module that is riveted behind everything else.  I
found a diagram of the alternator at http://tinyurl.com/6rx7so .  Yep,
the voltage regulator is inside (on item #2).  Looks like it might be
possible to open it up to replace just the "plate" holding the
regulator; however, the prices that I've seen for the regulator alone
are higher than the entire rebuilt alternator.

Splicing in a new plug wouldn't be a problem for me.  I'm very handy
with soldering and heatshrink tubing to make a solid inline splice.  The
problem would be getting the plug.  I don't know that a new alternator
would include a matching plug.  The rebuild that I bought last time
didn't include one.  If I don't get one spec'ed for my car, I'm also
guessing the mounting plates and holes won't line up.

After checking some other maintenance receipts to figure out what the
mileage might've been at the time I replaced the alternator, the 2nd
alternator now in the car (which was the rebuilt replacement from the
salvage shop with 1-year warranty) only lasted maybe all of 20K miles
which seems damn short.  The 72-month battery is only 16 months old.  Is
it possible a weak or defective battery would result in the voltage
readings that I saw (12.5V across the battery terminals with the car
running)?  It'd be easier to dump in a new battery than take off the fan
belts to remove the alternator and have to do it in reverse again.  Even
if the battery were defective, I still expected the voltage to rise when
I revved the engine.  Apparently to have the alternator tested at the
parts store means having to remove it from the car; i.e., they can't
test it /in situ/.

I have the following choices (for cheapest prices found so far), all of
which are rebuilds:

- ProStart brand: $118.99 (PepBoys; also at Advance Auto but I can't get
a price online and too late to call right now).
- Autolite (Pro-Tech) brand: $129.99 (Advance Auto or Checker Auto Parts
since both use PartsAmerica.com).
- O'Reilly Auto Parts (no brand identified other than "Ultima"): $119.

All have lifetime warranties.  The Autolite unit includes a roadside
assistance perk (with a $60 max reimbursement).  They didn't mention the
amperage rating so I'll have to check that tomorrow.  Any experience in
which brand or store you like best for an alternator?

Re: Alternator bad? Voltage regulator maybe?


VanguardLH wrote:
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Hi,
I'd rather think I in this case stand for integrated or imbedded.
If alternator is really proven bad, it can be rebuilt if you want to.
Or hen you bring bad one it's worh a few bucks in exhcange.

Re: Alternator bad? Voltage regulator maybe?


The only difficult part opening up an alternator is removing the pulley.
Only thing I found that always works is an impact gun.  Once the pulley is
off just remove those long bolts running through the case and everything
falls apart.  Just mentioning this if you decide to open it to inspect the
insides.  When a diode fails the battery "back drains" through the
alternator which I think is your problem.  Or at least part of the
problem.  There are companies out there that sell new connectors but the
easy way to get the newer connector is to just cut one from a newer
wrecking yard car.  You don't have a 90A alternator now.  Use to know the
amperage output but now guessing in the 75A range.  I have never had good
results with using rebuilds, or at least the kind sold at auto parts
stores.  Quality over the years has been very poor.  

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Re: Alternator bad? Voltage regulator maybe?


"johninKY" wrote in

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While I might attempt dismantling the alternator (although I don't have
an impact wrench), the deterring factor now is the high price for the
voltage regulator replacement part.  It costs more than the rebuilt
alternator, and the same price as a new alternator.  No point in buying
just the part when I can get the entire unit for the same or cheaper
price.  With a lifetime warranty (limited to the original car it was
installed in) and the much reduced price of a rebuild and the ease of
replacing the alternator (the belt and a couple bolts), I'll probably go
with the rebuild.  

Re: Alternator bad? Voltage regulator maybe?


VanguardLH wrote:
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Hi,
Sounds like your battery is drained by some unknown load or it is bad.
Probably one cell gone bad. If you can't test battery, try another one
then yo can decide. When charging the voltage should be ~14V. Is the
battery warm to touch?

Re: Alternator bad? Voltage regulator maybe?



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No warmth to the battery (when unused or with the car running).

Even if the battery was bad, wouldn't the voltage across it go up due to
output from the alternator (when the car is running)?

Re: Alternator bad? Voltage regulator maybe?


VanguardLH wrote:
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Hi,
No. because bad battery will load down the alternator like a partial
short. It happens when one electrodes inside battery cell shorts out.
Generally batteries cause more trouble than alternaotr/VG. Even brand
new battery can fail. One factor of better battery is mechanical rigidity.

Re: Alternator bad? Voltage regulator maybe?



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Took the battery to the car shop.  The first handheld tester said Good
(but a recharge was needed but I already knew that).  That included a
check for the short condition.  Then they shoved in the big tester that
first charges the battery for 30 minutes (ho hum, wander the store) and
it tested okay.  They also plug in the cold-cranking amp rating to check
the battery can supply that load (although 85F outside and 70F in the
store isn't really "cold").  Couldn't find my trickle charger at home so
picked up a 3-stage one at a different store where it was cheaper and am
charging the battery tonight.  That's because this car shop says they
can test the alternator while in-place but it requires the car can
startup on its own while testing.  They have an emergency jump kit to
let me start and drive back home but they need the car to be able to
start itself using the battery and alternator without being jumped.  So
tomorrow I find out more.

Re: Alternator bad? Voltage regulator maybe?


May want to read this.  Mitsubishi, not a Subaru, but essentially the same
design.

http://www.stealth316.com/2-alt-rebuild.htm

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Re: Alternator bad? Voltage regulator maybe?


Ok, just my 2 cents.

Before killing the alternator, a battery with a dead cell can prevent
the voltage from the alternator from going to normal charge levels when
measured at the battery.

Clean the alternator connections, make sure that the Alt S fuse
connections are clean, make sure that the connector that plugs into the
alternator is clean.  Make sure that the fusible link and main fuses are
clean.  Mind the ground connections and battery terminals as well.

Also, make sure that the v-belt is in good shape and that i has the
proper tension.  I have seen them slipping with no squeal.

Charge the battery and measure the voltage at the battery when cranking.
  It should be more than 9 volts.  When the motor is running, a properly
charged battery should see 14.2 to 14.8 volts in a properly regulated
system (those that allow batteries to last for 7 years, ;) )

Good luck!





VanguardLH wrote:

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Re: Any follow up?


johninKY wrote:

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Been busy replacing air conditioners, rebuilding windows, and cleaning
the yard of debris and hauling it away.  Just haven't gotten to working
on the car yet this week beyond getting the battery charged.  My buddy
is coming over (maybe) this Saturday or Sunday to help with more debris
(which reminds me that I have to get busy with the chainsaw) and getting
rid of a removed water heater.  Afterward, he'll accompany me when
testing the alternator just in case I need a ride back or a battery jump
(although the store says they have an emergency boost kit).  While some
car shops say the alternator must be removed, this one says they can
test with the alternator in place but the battery must be in the car and
capable of starting the car itself (no boost, no jump).  So, for now, it
looks like this job waits until this next weekend.

Hmm, come to think of it, I should put the charged battery back into the
car and connect it up.  If there is a leak in the wiring or other
component (or even through the alternator) then I might see this by next
weekend (although the battery might still be good enough to start the
car so I'm not sure this test will reveal anything).

Re: Any follow up?


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Before you reconnect the battery, put an ammeter in series with the
positive cable. You will see any current draw. If you get a current draw
pull the plug on the alternator and see if goes away.

Re: Any follow up?


Mike Copeland wrote:

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Good idea.  I've got an old ammeter (Amp Probe) that I inherited from
dad.

Re: Any follow up?


Mike Copeland wrote:

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Did as you mentioned.  The old ammeter didn't budge when I put it across
the "+" on the battery to the positive cable (with the negative cable
already connected to the "-" battery post), even on the 6A range.  That
seemed weird since I know the radio is still hooked up and has a clock
in it.  So I got out my DVM which has a 2A scale and it showed 0.438A,
or a little under half an amp.  Odd part was that it showed -0.438A
(with red probe to cable and black probe on "+" battery post), as though
current was running to the battery instead of out.  In any case, there
is a little bit less than an ampere showing on the DVM from the battery.

I left the battery disconnected until it's time to take in the car to
have the alternator tested.  My buddy isn't showing up today so maybe
tomorrow.

Re: Any follow up?


VanguardLH wrote:
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Hi,
Simple way to see excess ghost current is using a small 12V bulb in
seiries with battery cable. There is a very very small amount of current
flowing at all times for clock and such.

Re: Any follow up?


The DVM reading (-) is correct.  The battery being the source would read
drain current as positive if the red lead was connected to the battery +
post.

As far as the magnitude goes, did you read with all the accesories off?
  It strikes me as a tad high, was the dome light on? something else on?

Good luck.

VanguardLH wrote:
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Re: Any follow up?


AS wrote:

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Yeah, I figured that after thinking about it.  The current would go out
from the "+" battery post so the red probe on the DVM on there would've
been backwards to the electron flow.

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The only device that I know of that would've been on was the clock in
the radio.  No lights, including dome lights, were on.  The key was not
in the ignition switch so it wasn't even partially turned to enable some
of those circuits.  

I figured if a diode in the rectifier were shorted then that might be
the cause of the drain through it.  I found a basic schematic at:

http://www.alternatorparts.com/understanding_alternators.htm

If a diode were shorted, wouldn't that mean that there would be current
flowing through it (back to ground)?  I always thought a diode would
blow open due to the heat of the leakage current but then these are
high-current diodes and the leakage current is only half an ampere.

Re: Any follow up?


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The reason the amp draw may be a little high is because of the keep alive
memory in the radio and computer. Here's how to get around that. Hook up
your amp probe as before between the +post and +cable. Now take a jumper
wire and place it between the +post and +cable. Leave it there for at least
15 seconds (some take up to a minute). At this point your amp probe will
read zero. Once you remove the jumper wire the probe should read much lower
than in your initial test.

All that is moot though as I agree with JohninKY's original post, you have a
bad diode since it's only charging 12.5 volts. BTW... that shop that says
they can't jump the car, then test the alt is suspect. It sounds like they
have an idiot proof tester of some sort and only have idiots to test with.
;-)

 NAPA sells a very good reman alt with a lifetime warranty. Be sure to ask
for their premium line as they also have a cheaper line with a 3 year
warranty. They also sell a new one for many applications for not too much
more.


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