Gilbert said:I am in UK, so quite possibly the US market is different. Do you have
charges based on CO2 emissions ? Are you using daytime driving lights,
or aircon frequently ?
When I talked to Subaru UK they were quite open about it, in fact I
only had to say I was monitoring the battery voltage and they went on
to describe exactly what I was seeing, and the things they had tried
while trying to fix it.
Gilbert
Hmmmm,Carl said:I have yet to experience a dead battery (due to my own negilgence OR the
'smart voltage regulatoer' issue you mention) in my '06 WRX. If the
system was incapable of keeping the battery charged, shouldn;t I have
had a dead battery several times by now?
I'm in the US - are you? Could this be specific to another market?
Carl
Tony Hwang said:Hmmmm,
Really? 3 Subaru cars in my family all later than '06 don't have that
problem. Driving with lights on? We have DRL. Fan on? most of time it's
on by default. Lemme see, typical alternator is 3 phase rull wave
rectified and it's output is controlled by field coil current supplied
by imbedded regulator. If yoy measure voltage going to F terminal of
alternator, you'll see whether it is charging or not and how hard it is
charging. As simple as that.
Gilbert said:Sorry, the field current is definitely controlled by the ECU since 04.
Monitoring the field current is an indication of the current being
delivered by the alternator, yes, but not an indication of battery
charging current. The voltage across the battery terminals shows this.
Rick Courtright said:Hi,
Something doesn't pass the "sniff test" here. Even the inafamous old
positive earth Lucas systems weren't any more bass-ackward than that
idea... dunno how the rest of the world runs their domestic market
alternators, but I'd be hard pressed to think of one, domestic or
imported, we have in the US today that doesn't have an integral voltage
regulator. Now, I'd understand the ECU monitoring output voltage so it
has a base line for comparison when it receives its various signals from
this sensor and that, but using the ECU to do the job of the voltage
regulator makes zero sense to me at this moment. Maybe I'm missing
something important?
IF the alternator IS putting out adequate current and voltage, but
you're not getting what's required at the battery, WHERE is the loss?
That's the question I'd be asking myself if it were my car.
Rick
Gilbert Smith said:Subaru tell me the alternator is taken off-line a.s.a.p so that it
presents no load to the engine during the emissions test, thereby
getting a better score. They say there is no voltage regulator inside
the alternator because the ECU controls the field current.
They also tell me that turning on the blower to its lowest setting is
programmed to restore normal generator action. I already proved this
myself, and driving lights will do it also.
Don't forget this is an 05 car in pristine condition, and it passes
the Subaru electronic test equipment run with flying colours.
Bottom line is if you have an 04 or later car, and rarely use the fan
or the lights, you end up with a flat battery - believe me, I know.
Gilbert.
Hi,Gilbert said:Sorry, the field current is definitely controlled by the ECU since 04.
Monitoring the field current is an indication of the current being
delivered by the alternator, yes, but not an indication of battery
charging current. The voltage across the battery terminals shows this.
I posted one reply at the top (sorry) - here it is again:
I just talked to the Subaru importers, and they know all about this
problem, including having looked for ways of fixing it without
modifying the ECU software. They can offer no solution other than
driving with the fan or lights on all the time. Apparently it affects
all models since 2004, and is due to trying to get the best results
from carbon emission tests by keeping the generator off-load.
Gilbert
Hi,Rick said:Hi,
Something doesn't pass the "sniff test" here. Even the inafamous old
positive earth Lucas systems weren't any more bass-ackward than that
idea... dunno how the rest of the world runs their domestic market
alternators, but I'd be hard pressed to think of one, domestic or
imported, we have in the US today that doesn't have an integral voltage
regulator. Now, I'd understand the ECU monitoring output voltage so it
has a base line for comparison when it receives its various signals from
this sensor and that, but using the ECU to do the job of the voltage
regulator makes zero sense to me at this moment. Maybe I'm missing
something important?
IF the alternator IS putting out adequate current and voltage, but
you're not getting what's required at the battery, WHERE is the loss?
That's the question I'd be asking myself if it were my car.
Rick
Hmmm,Gilbert said:Subaru tell me the alternator is taken off-line a.s.a.p so that it
presents no load to the engine during the emissions test, thereby
getting a better score. They say there is no voltage regulator inside
the alternator because the ECU controls the field current.
They also tell me that turning on the blower to its lowest setting is
programmed to restore normal generator action. I already proved this
myself, and driving lights will do it also.
Don't forget this is an 05 car in pristine condition, and it passes
the Subaru electronic test equipment run with flying colours.
Bottom line is if you have an 04 or later car, and rarely use the fan
or the lights, you end up with a flat battery - believe me, I know.
Gilbert.
Bruce Armstrong said:Sorry for top posting.
Instead of insulting Gilbert, do as I did yesterday and google "ecu control
field current alternator" or similar.
The ECU does indeed control the field current on many alternators these
days. The idea is to effectively turn the alternator "off" or control it to
only produce the current actually needed, apparently by applying square wave
pulses of varying width as field current. It will turn the field off at
full throttle to lessen the load on the engine, for example, when you have
drive by wire throttle. That started in 2004 on Legacies, dunno about the
rest of the line.
The ECU gets its electrical load info from the body control modules,
electronic blocks that react to switch settings on the dash, steering wheel,
climate control and the RFID keyless entry system. My Legacy has several of
these modules up behind the dash, and you have to add a couple more if you
want memory on your power seats and remote start. Amazingly, Subaru expects
you to hold these extra things in place with plastic ties around the
steering column, and the wiring makes my head ache. Got the .pdf for
installing the remote start from subarugenuineparts online, and decided I
can brave the snow instead!
The voltage regulator itself is of course still in the circuit to control
the voltage produced after the change from 3 phase AC to DC at the current
output prescribed by the ECU.
What Gilbert has discovered in his particular car is that unless there is a
minimal load at all times, like the fan, or here in Canada DRLs, the system
goes into some kind of funk mode and allows the battery to go flat. I guess
the solution in his case is to always run a load. I assume something else
is wrong, maybe with his ECU and how it interfaces with the alternator,
because one would hope that Subaru would have covered the scenario where
there is no electrical load beyond the ignition system. But maybe not.
The dealer should know more, but we have all run unto dumb dealers.
Bruce Armstrong
Tony Hwang said:Hi,
You are full of it. You don't even know what you are talking about.
Amount of field current controls the output of alternator. It's closed
loop servo kinda circuit if you see this electro mechanical device as a
electrical simulation. Read your post, ---field current is an indication
of the current deliverd by the alternator---- What does that suppose to
mean? Do you know what field coil does? Do you know what stator windings
do? I think your Subie dealer is full of it too. I live in Foothills in
Western Canada. If charging system does not perform well we can even
start our cars in the morning with dead battery with slush formed
inside. Poential difference(voltage) makes the current flow. Ever looked
into dynamic parameters when alternator is under load and charging at
the same time. Battery voltage sensing line, F terminal, lternator
output terminal, temerature compensation status, etc. with proper
instrument.
Bruce said:The ECU does indeed control the field current on many alternators these
days. The idea is to effectively turn the alternator "off" or control it to
only produce the current actually needed, apparently by applying square wave
pulses of varying width as field current. It will turn the field off at
full throttle to lessen the load on the engine, for example, when you have
I frequently end up with a flat battery in my Forester05, despite the
garage test rig reporting that the alternator and battery are in
perfect condition.
What am I doing wrong ? I am driving without the heater fan or
sidelights on. If you run the battery low by parking with the lights
on (say), there is no way the battery will ever recover unless you
drive with the fan on. (I am not joking). Short journeys or long.
Charging lead-acid batteries is not rocket science, all you do is put
14.6v across the terminals until the charge current shows it to be
fully charged, then maintain a 14.2v trickle charge. Try plugging a
voltmeter into your cigar lighter socket and watch what happens on
your lovely Subaru, then compare it to any other make.
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