Subaru Outback Forums banner

1 - 18 of 18 Posts

·
Registered
Joined
·
33 Posts
Discussion Starter #1
So battery light came on and decided it was time for alternator. Done. Day later again, battery time. All good. No. Maybe bad alt. replaced. Since then the range seems to be between 12 and 14 volts. Light has not come back on since cleaned all the grounds and terminals. Is there a range of volts that subarus operate at? Two of my other vehicles both run at 14 volts at idle or 1500 2000 rpm. Just find it odd that suby runs at 11.5 -14 volts and not 14 volts. Time will tell. Is this common. Thanks jim
 

·
Registered
Joined
·
16,295 Posts
It should be much the same as your other cars -- around 14 V.

See http://www.subaruoutback.org/forums/110-gen-2-2000-2004/47323-dont-tell-me-these-things-dont-have-feelings-2.html#post454781. It too was about low voltage with a replaced alternator in a 2002 H6, where finally, after several aftermarket rebuilts were tried, and lots of measurements posted as part of our discussions, installing an original Subaru H6 alternator did the trick. Seems the aftermarket rebuilts somehow are not compatible with the H6 system. (It's a long thread, and one I won't likely forget . . . .)
 

·
Registered
Joined
·
4,439 Posts
My ultraguage shows just over 14V when I am driving.
 

·
Registered
Joined
·
187 Posts
Anywhere from about 12.5 to 14 volts is a normal voltage at idle. Some vehicles are closer to 12 while some idle at 14+. I haven't tested my new Subaru voltage so I don't know what the normal is for Subaru.

If all of your terminals are very clean, the battery is new, and the alternator is new, and you get 12.5 volts or more at idle at 14+ while driving, I'd say your good to go.
 

·
Registered
Joined
·
7,355 Posts
Alt output test is @1800 rpm everything on parked, and i mean everything, 13.5 volts or more. A little lower you have dirty or bad battery terminals.
 

·
Registered
Joined
·
33 Posts
Discussion Starter #6
Volts

Wow never thought that a reman would create this much trouble. Seems remains not compatible with subys. We'll continue to monitor and see what happens. I would assume that no lights everything's ok. Thanks for the help.
 

·
Registered
Joined
·
16,295 Posts
I would assume that no lights everything's ok.
I'm not sure I'd make that assumption. That was the case (no BATT light) in the linked thread, but it seems clear the problem was the rebuilt alternators.

Nevertheless, check the ground system in operation: Run the engine at an elevated rpm (1000 or more) with some load (headlights etc) turned on. Measure the Voltage from the battery negative post (not the cable clamp) to: a) the car body; b) the engine block; and c) the alternator housing. The Voltage should be not more than a few tenths of a Volt, and typically, far less. If it's higher, there's poor ground connections. If all is good, then I think you're facing the same or similar aftermarket/rebuilt alternator incompatabilty as pookie2 (linked thread).
 

·
Registered
Joined
·
514 Posts
Any vehicle I ever tested while engine running is about 12.5 to 14 volts, never higher than 14 volts, using a digital multimeter.
 

·
Registered
Joined
·
16,295 Posts
If the Voltage at the battery posts is continuously running around 12.5 Volts, the battery charge is not being maintained. The alternator is designed to put out a higher voltage in order to both supply the running needs of the engine and accessories AND to maintain the full charge on the battery so that it's able to start the car the next time.

According to the Subaru service manuals I have, the alternator regulating Voltage (Voltage at the alternator terminal) should be between 14 and 14.8 Volts, and if the connections are good, it should be close to that at the battery posts.

If the engine is idling and there's some accessories or lights on, it is possible that the Voltage measured at the battery posts, or at other points such as the accessory power outlets, will be down to around 12.5 V, but with the engine rpm raised, it should be close to 14 V. (There will always be some Voltage drop between the alternator and the measuring point, if that's at the battery or a power outlet. The spec for the alternator is at the alternator terminal. Nevertheless, if the alternator is putting out 14 V, there shouldn't be a 1.5 Volt drop in the wiring between the alternator and the battery.)

In the thread I linked in post #2, the final outcome was that the genuine Subaru alternator delivered 14 Volts where the parts store rebuilts didn't.
 

·
Registered
Joined
·
514 Posts
In the thread I linked in post #2, the final outcome was that the genuine Subaru alternator delivered 14 Volts where the parts store rebuilts didn't.
plain OM, that is worth remembering, I shall purchase a Subaru alternator when ours finally goes!
 

·
Registered
Joined
·
16,295 Posts
. . . that is worth remembering, I shall purchase a Subaru alternator when ours finally goes!
The problems experienced in the linked thread were with an H6 engine, which uses a different alternator, a distinct aspect of which is that it's controlled (at least in part) by the ECM. This is not the case with the H4.

Although there have been reports here of H4 rebuilt units not functioning properly, I wouldn't say that all parts store H4 alternator replacements should be suspect.

Incidentally, does your on-line service manual have a section on testing the alternator, and if so, what does it say for your 05?
 

·
Registered
Joined
·
210 Posts
The "ideal" voltage with the engine running above idle speed should be 13.8 V. Anything between 13.5 and 14.2 V is perfectly acceptable and normal. Between 13.5 and 13.2 V, and between 14.2 and 14.5 V is marginal - it won't cause any immediate damage, but will reduce your battery's capacity and lifespan. Below 13.2 and 14.5 V is bad.

Your should let the engine run for a minute or two before measuring the voltage. It's normal for the voltage to be on the high side for the first minute after starting the engine (somewhere between 14.2 and 14.5 V).
 

·
Registered
Joined
·
22,836 Posts
The "ideal" voltage with the engine running above idle speed should be 13.8 V. Anything between 13.5 and 14.2 V is perfectly acceptable and normal. Between 13.5 and 13.2 V, and between 14.2 and 14.5 V is marginal - it won't cause any immediate damage, but will reduce your battery's capacity and lifespan. Below 13.2 and 14.5 V is bad.

Your should let the engine run for a minute or two before measuring the voltage. It's normal for the voltage to be on the high side for the first minute after starting the engine (somewhere between 14.2 and 14.5 V).
^ what he said. Same voltage applies to any car or boat by the way.
 

·
Registered
Joined
·
33 Posts
Discussion Starter #14
Volts

So just got back from Subaru and did a battery test. 11.3 no load 11.0 at load. Got half way home and went downhill from there. Car completely dead in my. Driveway. Wait couple minutes and starts right up. Wtf. How do you go from all to nothing like that. Seems as if the alt. discharges at speed and once it's off ok. Never seen or heard of anything like this. Hate to spend upwards of $500 for oe but looks like I might have to. Thanks for the input and see what happens. Has anyone found an oe on the internet? Thanks jim
 

·
Registered
Joined
·
16,295 Posts
So just got back from Subaru and did a battery test. 11.3 no load 11.0 at load. . . .
Were you at a dealer? What did they say?

Car completely dead in my. Driveway. Wait couple minutes and starts right up. Wtf. How do you go from all to nothing like that.
A typical car battery is designed to deliver a high current for a short time, such as is needed to start the engine, and then "rest" while the alternator takes over both replenishing what was used and providing for the ongoing operation of the engine and other electrical loads in the car. But the battery is not really good for continuous discharge at the rate needed to run the car in the absence of the alternator's output. It all has to do with the way the battery actually works -- simply, electrical energy is "stored" (when the battery is charged) by a chemical transformation inside the battery, and then to recover that energy for use, the chemical activity has to be reversed. The battery can retain some electrical energy ready to go (e.g. for starting) but then the reverse chemical process has to ramp up to keep the battery delivering current. If it can't keep up, the battery Voltage dies away. If the load is removed and there's time for the chemical reaction to function, it can once again start the car. (But it probably won't last long if the alternator doesn't take over.)

It sure sounds as if that alternator isn't doing it's job. It could be the same situation as in the linked thread (post #2) -- the alternator starts out looking okay, but after a while seems to give up, leaving the battery to run the car.

As has been mentioned in other posts here and in the linked thread, to be sure, the wiring between the battery and the alternator should be verified. One of the ways is to measure the voltage between the battery negative post and the alternator case, and between the battery positive post and the alternator output post, when the engine is running above idle, there's some additional load (lights, heater fan etc), and the alternator output Voltage appears reasonable (i.e., above 13 Volts). The two Voltage measurements shouldn't be more than a few tenths of a Volt each.

The alternator you have now certainly doesn't seem to be doing its job, so it should go back. I wonder if they can identify the rebuilder, and maybe find an alternator from another source. That might be worth a try.

An original alternator from a scrap yard is a possibility if they are sure it comes from a similar H6. Or if there's a pick-and-pull scrap yard near you, that might be another way, that is, if you can find a similar H6 with the alternator still in it. Granted, it does entail some risk.

Perhaps someone here has one that you could strike a deal for.

The only reliable alternative seems to be getting a replacement from Subaru. I wonder if there are "genuine Subaru rebuilts" that I would expect should be done properly and equivalent to new.
 

·
Registered
Joined
·
16,295 Posts
Caveat

I thought I should add that all the references to what is, or should be, the "proper" Voltage at the battery or alternator are usually with a battery that is at 75% of full charge or more.

If a battery is discharged, the apparent alternator output Voltage will be lower.

For example, if a battery is run down and the car needs a boost to start, right after the car starts the measured Voltage can be significantly below the expected normal level, and will (or should) start to come up only after the alternator has a chance to build up the battery charge. The time will depend on the load from the engine and the rest of the car electrical functions, and the alternator's capacity, which is based in part on the rpm. It will also depend on the underlying condition of the battery.

If, in the above case, the battery is discharged to around 11 Volts, once the car is started, the Voltage might remain below the normal level, and any measurements will not be indicative of a malfunctioning alternator.
 

·
Registered
Joined
·
146 Posts
I had all kinds of weird electrical issues with my '02 VDC a couple of years ago. It would start with the compass going out, VDC and ABS turning off, followed by the tach and speedometer going crazy. If I kept driving my lights would all dim and my transmission would start shifting poorly before it would finally die. All of this would happen in a couple of miles. I cleaned up the grounds and that didn't fix it. My voltage would be anywhere from 11-14 with-in minutes of eachother. Finally I replaced the alternator with NAPA's premium rebuild and I haven't had any issues since. I think the NAPA one even puts out a couple more amps than the stock OEM one.

ETA: I think this was the one I bought.
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=RAL139538_0209556960
 

·
Registered
Joined
·
33 Posts
Discussion Starter #18
So Subaru said the voltage at the battery was low at idle. Otherwise ok. Car died on the way home. Picked up a mitsibishi alt. at a junk yard on the way home put it in and so far everything back to normal. Will drive for the next couple days to see how it reacts. Did several tests with the new alt. and all the readings look very promising. Cold start at 14.0 amps. Several minutes later with all acc. On no lower than 12.0 at idle. 13.0-.5 at 2000 rpm. Keeping my fingers crossed but all looks good. Never would imagine all this from an reman alt. by the way this was a napa premium. Thanks for all the help.
 
1 - 18 of 18 Posts
About this Discussion
17 Replies
9 Participants
scooby6
Subaru Outback Forums
Welcome to the Subaru Outback Owners Forum, we have tons of information about your Subaru Outback, from a Subaru Outback Wiki to customer reviews.
Full Forum Listing
Top