9 volts on Tribeca- can a bad battery cause low alt voltage?

[idosubaru]

Can a bad battery cause a low alternator output?

I get 9 volts while running, belt and balancer look fine.

Is that definitely alternator or could be battery?

Edited June 26, 2022 by idosubaru

[lmdew]

Check all the connections, clean and tight.

Load test on the battery.

Have the Alt Tested.

 

[idosubaru]

Measured 9 volts at battery terminals and at alt output. Test more when I get home or take battery in tomorrow for testing  

Trying to decide wether to make it home I’d rather not try to find a battery Sunday night. I guess Walmart is open, but I try hard to avoid that hole. Lol

Edited June 27, 2022 by idosubaru

[lmdew]

Hope you made it.

 

[forester2002s]

What voltage do you read at the battery terminals, with everything off, engine not running?

If you have normal battery voltage  (~12V), then I would also suspect a failing battery.  My logic is that to get to ~12V, the alternator must be charging properly, otherwise where does the ~12V come from?

Edited June 27, 2022 by forester2002s

[idosubaru]

On 6/27/2022 at 7:14 AM, lmdew said:

Hope you made it.

 

Yep. Installed a new battery, it was 6+ years old though it did charge back up fine. Used genius boost for starting, pulled day time running light fuse, tried to avoid brake pedal (to limit rear tail light usage).  Made it home, put it on charger, drove to work today with no alt.  I'll keep doing that until the ordered one arrives in the mail.

 

On 6/27/2022 at 11:30 AM, forester2002s said:

What voltage do you read at the battery terminals, with everything off, engine not running?

If you have normal battery voltage  (~12V), then I would also suspect a failing battery.  My logic is that to get to ~12V, the alternator must be charging properly, otherwise where does the ~12V come from?

6 cylinder subaru's use a three wire alternator (4 cylinders are 2 wire and simpler) with reference voltage the ECU uses to affect alternator charging.  In rare cases the alternator will put out less, like 9 volts, due to poor grounding compromising that reference signal. Measure the voltage at the battery posts and ground via the alternator body.  If there's a large voltage difference there's a reference wire grounding issue. 

It's really rare and I assumed it was the alternator, but it was a good opportunity for me to experientially learn to test for it. I've worked on some triple digit number of Subaru's so there's a reasonable chance I'll see it some day and part of my seemingly irrelevant questions. 

Edited June 28, 2022 by idosubaru

[idosubaru]

Drove one hour, 30 mile round trip, mountain roads on just the battery today while starting with the NOCO genius boost. Battery showed 12.47 V when I got home. 

[jonathan909]

This shouldn't be taking this long to sort out.  When you say "on just the battery", what do you mean?  That you had the alternator disconnected?

[idosubaru]

13 hours ago, jonathan909 said:

This shouldn't be taking this long to sort out.  When you say "on just the battery", what do you mean?  That you had the alternator disconnected?

It didn’t take long, I ordered an alt right away. I also wanted to clarify how 3 wire alternator reference voltage issues may differ from typical 4 cylinder 2 wire alts when testing. I realize most people don’t care.

Alternator is connected, but output is zero even at high rpm. 

[jonathan909]

1 hour ago, idosubaru said:

It didn’t take long, I ordered an alt right away. I also wanted to clarify how 3 wire alternator reference voltage issues may differ from typical 4 cylinder 2 wire alts when testing. I realize most people don’t care.

I appreciate that it may not always be the best approach, but it's usually how we roll:  Don't bother with extremely detailed minutae that's only going to be useful once in a lifetime - until you need to.

1 hour ago, idosubaru said:

Alternator is connected, but output is zero even at high rpm. 

Okay, this is getting stupid.  I'm irritated by the idea that the ECU should somehow be involved in making an alternator run, because it's easier not to put it in the loop.  Leave well enough alone and don't be a busybody engineer getting a computer in the way of things that don't need a computer - it only reduces reliability.  Before I crack the schematics out of sheer annoyance, have you checked all of the alternator wires end-to-end for shorts and opens?  Do you see the same voltage at both ends of each of those wires with the engine running?

[jonathan909]

Just so I'm looking at the right drawing, which year is it?

Edited June 30, 2022 by jonathan909

[1 Lucky Texan]

CAFE rules kinda force manufacturers to do some weird things. I doubt Ford wanted to make an aluminum truck.....

[jonathan909]

I'm not sure I buy that argument.  Might be a factor, but there are just too few engineers out there who know when to take a step back and say, "I know I can do this.  The question is, should I do this?"

Ford:  I just finished a timing job on my daughters' '05 4.0 V6 Mustang (the plastic chain guides went to pieces).  We had to pull the motor to do it because those morons took a perfectly good V6 and made it OHC by replacing the usual V cam (with lifters and push rods) with a jackshaft that in turn feeds the cams, one of the chains for which is at the back of the block.  As if that isn't bad enough, we had to buy a special toolkit to time it because none of the timing sprockets are actually keyed to their shafts and are kept in time by hugs and prayer.

And on their aluminum trucks:  I know an aeronautical engineer (through sailing - he used to build Tornado catamarans).  This is a brother who knows his alloys.  I told him the ads for those trucks made me yell at the TV, and here's his reply:

> Incidentally, the Canadian TV commercials for the Ford F150 truck
> boasts that the body is made of Military grade aluminum.  There is
> no such material as military grade aluminum, so it must be a figment
> of some marketeers imagination.  Who would knowingly buy a truck
> with a body made of an imaginary material?

 

Edited July 1, 2022 by jonathan909

[idosubaru]

19 hours ago, jonathan909 said:

I'm irritated by the idea that the ECU should somehow be involved in making an alternator run, 

Yes. Cheers! Preach it!  That's one reason I've paid attention to these 3 wire alternators over the years, asking/paying attention to comments about them.  Why? How does this impact testing?  Can they be swapped with 2 wire alts?  I haven't heard good reasons for why. 

18 hours ago, jonathan909 said:

Just so I'm looking at the right drawing, which year is it?

06 but I think all 6 cylinder Subaru's are this way - I think my H6 outbacks are the same.  IOW it's a "feature" of the higher end trims. LMAO

 

7 hours ago, jonathan909 said:

 

And on their aluminum trucks:  I know an aeronautical engineer (through sailing - he used to build Tornado catamarans).  This is a brother who knows his alloys.  I told him the ads for those trucks made me yell at the TV, and here's his reply:

> Incidentally, the Canadian TV commercials for the Ford F150 truck
> boasts that the body is made of Military grade aluminum.  There is
> no such material as military grade aluminum, so it must be a figment
> of some marketeers imagination.  Who would knowingly buy a truck
> with a body made of an imaginary material?

Your friend is right - The nature of metallurgical grades make it a stretch to act like it's better than steel or offer value for a new truck buyer. He is right, but in the way us engineers are right when we (I have to try hard to be self aware and manage this) complain about marketing, management, business, accounting, law, social matters and other topics where we talk like we can do another persons job better than others and can't see the forest for the trees. Meanwhile all those other departments are complaining about us engineers social skills, designs, attitudes, complaints, critical nature...see previous comments about the 3 wire alternator. Although Aero's generally don't know alloys.  Specifically one individual may, but academically they often have one basic materials 101, or none. 

"Military Grade" or military reference has been used for decades as marketing tools, some more accurate than others. Over zealous marketing works and should surprise no one, particularly well educated people. People today have highly tuned BS meters, marketing is closely aligned with "might be somewhat true" now. We've moved from suggestive to directly disingenuous. Marketing researches how many adds people see, what it takes to get through the sheer volume. My favorite marketing pro comment ever that is never heard outside of board rooms: "The best consumer is an unhappy one".  Welcome to 2022.   At a minimum the Military does "spec" things to the extent their process doesn't allow a manufacturer to use a bunch of road side cans smashed together to build a rotor. And there are existing generic aluminum grades that are used by the military. So here are two expanded constructions of the phrase "Military grade":

1. military *only* grade

2. Military *uses this* grade

This is an over simplification and stepping out of the metallurgical weeds, but at least makes it easier to see. When truncated by the asterisks, both of those sentences say "military grade" but mean different things.  Again, over simplification, but your friend is rightfully arguing for a #1 interpretation since that's almost implied, while Ford is taking......(drum roll please) A NUMBER 2!   (comedy points please!).  (hit the cymbals). 

Speaking of fun, crushable, cans - the perception most Americans have of aluminum - is crush beer cans Friday night, "my machinist won't touch aluminum, says it's garbage" and "aluminum welds like !)(*)%!", or "i hate aluminum I have to carry two welders" or "remember that bent Iphone ad - I bow down to the competition, that was brilliant!".  Ford was wise to make some steps to temper perception of aluminum for new truck buyers. I got phone calls when those ads and trucks came out (by friends who currently own them). And who cares - I don't think anyone believes their aluminum truck will be a military tank, bullet proof, or will surpass steel.  If they do, like many over zealous high expectation consumers, they'll just trade it in and move on. If there's a problem there are lemon laws, warranties, recalls, TSB's, and truck body parts and beds are 100 times easier to replace than a Subaru rear quarter panel. 

 

[jonathan909]

All on the mark.  I'd say, though, that you're probably being overly generous in your lexical interpretation.  Simple fact is that alloys are described (by number) in the UNS, and within those alloys there are grades, and the word "military" has no place at all in that taxonomy, hence Geoff's highly amusing dismissal.

Of course, GM did a much simpler takedown of that twaddle in their ad, in which they pitched an empty toolbox into the back of an F-150, resulting in a hole punched in the bed.  Sadly, Mencken (though it's been more broadly attributed in various forms) remains right:  "No one in this world... has ever lost money by underestimating the intelligence of the great masses of the plain people."  The F-150 remains the best-selling vehicle in North America.

But we're getting pretty OT here.  Lemme pull that schematic.

[jonathan909]

On 6/28/2022 at 2:29 PM, idosubaru said:

6 cylinder subaru's use a three wire alternator (4 cylinders are 2 wire and simpler) with reference voltage the ECU uses to affect alternator charging.

It looks like this is going to take a little digging, because the relevant circuits are spread across a bunch of pages all over the manual.

However, at first glance I'd question the above statement.  If you arrived at "reference voltage the ECU uses" by reading "REF. TO ENGINGE (sic) ELECTRICAL SYSTEM [E/G-01]" on the schematic, my interpretation would instead be "refer to engine electrical system drawing", based on similar indicators on the schematic.

Edited July 1, 2022 by jonathan909

[jonathan909]

I think that anyone interested in figuring out the difference (I include myself, but don't have an H6 running at the moment - it's next in the garage queue) should take a look at that extra alternator signal.  Pin 3, black w/ red tracer, goes to pin C10 aka pin 10 of ECU connector B136 (this is the '06 Tribeca).  My guess would be that it's an output that the ECU senses, but I could be wrong.  Throw a meter on it.  Try disconnecting it, probing the two sides to see which side is driving and which is listening, see what the ECU thinks of that signal going away and whether the alternator continues to output properly.  Should be able to figure out pretty fast whether it matters.

[forester2002s]

Lots of stuff online about 3-wire alternators.

Here's one: Alternator System in Your Subaru

[1197sts]

I recently went through an extended period of troubleshooting a charging problem on a 2001 LL Bean (3 wire system). To make a very long story short it was a bad alternator. It started out intermittently with several warning lights flashing, eventually total loss of charging. When measuring voltage at the battery it should read approx 14 to 14.5 volts when initially started, and depending on load and state of charge will then modulate between approx. 12v to 14.5v. When we had the total failure the voltage while running was erratic, but less than 10v. 

There are people who have de pinned pin C (black/red wire), and the car electrical system works fine. Some say this is hard on the system, but apparently the internal voltage regulator in the alternator works just like the 2 pin systems in the 4 cyl cars where there is no signal at pin C which should produce approx. 14.5v with no problem. There is also some info floating around about a Subaru service bulletin for certain Foresters that changes the signal to the ECU, simulating a load, presumably to  influence the signal at pin C. I have also read several reports of people trying to determine what the signal is supposed to be at Pin C, there does not seem to be a consensus on what the signal is supposed to be.

There are tons of people that have had trouble fixing charging issues with the H6 I think a lot of it is due to not understanding the system. Also the aftermarket alternators have a bad reputation. Also I don't think the local parts store can do a good test on a 3 wire system, most don't know what it is.

[idosubaru]

3 hours ago, 1197sts said:

I recently went through an extended period of troubleshooting a charging problem on a 2001 LL Bean (3 wire system). To make a very long story short it was a bad alternator. It started out intermittently with several warning lights flashing, eventually total loss of charging. When measuring voltage at the battery it should read approx 14 to 14.5 volts when initially started, and depending on load and state of charge will then modulate between approx. 12v to 14.5v. When we had the total failure the voltage while running was erratic, but less than 10v. 

There are people who have de pinned pin C (black/red wire), and the car electrical system works fine. Some say this is hard on the system, but apparently the internal voltage regulator in the alternator works just like the 2 pin systems in the 4 cyl cars where there is no signal at pin C which should produce approx. 14.5v with no problem. There is also some info floating around about a Subaru service bulletin for certain Foresters that changes the signal to the ECU, simulating a load, presumably to  influence the signal at pin C. I have also read several reports of people trying to determine what the signal is supposed to be at Pin C, there does not seem to be a consensus on what the signal is supposed to be.

There are tons of people that have had trouble fixing charging issues with the H6 I think a lot of it is due to not understanding the system. Also the aftermarket alternators have a bad reputation. Also I don't think the local parts store can do a good test on a 3 wire system, most don't know what it is.

Excellent - thanks for posting that.  I just get low mileage OEM units, I won't install aftermarket on alternator on a Subaru unless i absolutely have to. 

[1997reduxe]

Thank you for this post and all the replies. I have a 2002 L.L. Bean H-6 Outback that I’ve been having all kinds of electrical problems with. I can see this is going to be more complicated than my old 2.2 legacys.

👀

[1997reduxe]

I’ll post my story about what happened with my alternator just so that anybody who finds this post in the future can hear what happened to me. This message board has mentioned in it and this post I haven’t been here for a while but it used to be my favorite place for Subaru stuff. It still is. 💚

Well I kind of fixed it myself. I guess it wasn't the battery by itself after all. I replaced the battery two Thursdays ago if you remember. And the car ran OK since then, except the lights were still coming on the battery light and the brake light to be honest with you I realized this car has had electrical problems for the whole time I had it and that's about a year. And when I got the car from my mechanic he gave me another alternator to take with me that was he said it was new but I could tell it was probably new used. I don't know if he was going to put it in the car and just didn't get around to it or whatever. So Saturday morning I went to get tacos while it was still dark out at 6 o'clock and I went down a couple miles down the highway and just in that length of time it was ready to die from no electricity. I had to shut the lights off and use no turn signals or anything just to get back to my house. I had already been planning on maybe replacing the alternator. So it was in my car. And I went through the process of doing it by watching a YouTube video luckily I could do it. I noticed when I was taking the little connector off of the alternator not the one that bolts on but the one that comes off in a plastic housing that the plastic housing was cracked. But it was still usable I'm gonna get a new one.
I was researching about it Friday night after work when it was already having problems and it turns out this car, The H-6 version of the outbacks after 2000 or so, they have a different wiring set up compared to the earlier versions which other ones I owned all the time I've had these cars. The ones from the 90s with the 2.2 and the 2.5 engines. The older ones have a two wire system going to a lot of the wiring the lights the alternator but I guess especially with the H6 they went to a three wire alternator. So one wire to ground I guess one wire to power and one wire to the computing system. So all of the wiring and devices on the car are also wired into the computer. I'll post a link about it below if you want to look at it it's pretty interesting actually I'm glad I saw it before I tried to do it. Because the reason I'm saying this is the one guy comments that when you take these cars in to get the alternator checked, a lot of the basic standard places that people get parts like AutoZone etc., don't have the ability to know how to test a three wire alternator. Also, they said that these outback's since they had this more enhanced wiring system, they had a lot of problems with breaking ground wires etc. going back to the back hatches and the rear lights and all of that. That they were notorious for the wires in the hatches breaking and things. I can very easily see that and now this car is basically 20 years old. So I was imagining a nightmare of trying to figure out what the problem is. Well luckily for me, I replaced the alternator and when I did it I noticed that the wires inside the little connector that I said was broken that connects into the alternator they were all corroded like not really badly like they were eaten away but they had a lot of dirt and a lot of corrosion that happens on electrical systems. And I didn't have any baking soda to make into a solution to wash them with but I did have some Arm and Hammer baking soda toothpaste which I used. With a toothbrush and water and believe it or not it worked. I washed down inside the little connectors that connect to the prongs that come out of the alternator and I did it about four or five times. And then rinsed it all off and connected it up to the new or new used alternator, and believe it or not it seems to have solved all the problems. Just telling you this so you can know for your future because I guess the six-cylinder Subarus can be a pain. Thank you for your help by the way. I will still contact you if I need other work done.
 

[heartless]

Any time there are flickering dash lights on a Subaru (possibly other makes as well) one should suspect the alternator. This is true from the old GL/DL days right on thru to present - makes no difference if it is a 4cyl or 6 - the symptoms are pretty much the same.

I have said this before, but it bears repeating....
A bad battery can kill a good alternator - and - a bad alternator can kill a good battery..  the two are very closely related.

troubleshooting the problem can be as simple as making a trip to your local chain auto parts store (Advance, O'Reilly's, etc) and asking them to do a charging system check.
Granted, there are occasions when the alternator shows ok on one of these tests, but is still bad.. have had it happen to me personally.. the alternator was only failing under very specific circumstances, but I still had the flickering dash lights (especially noticeable at night) which led to a correct diagnoses.

Generally speaking, aftermarket alternators for Subarus are usually crap and fail pretty quickly. I have had excellent results getting a stock alternator rebuilt at a place that specializes in such work.. cost was comparable to a "new" aftermarket unit at a parts store, but far more reliable.

[jonathan909]

On 9/18/2022 at 7:31 AM, 1997reduxe said:

Well luckily for me, I replaced the alternator and when I did it I noticed that the wires inside the little connector that I said was broken that connects into the alternator they were all corroded like not really badly like they were eaten away but they had a lot of dirt and a lot of corrosion that happens on electrical systems. And I didn't have any baking soda to make into a solution to wash them with but I did have some Arm and Hammer baking soda toothpaste which I used. With a toothbrush and water and believe it or not it worked. I washed down inside the little connectors that connect to the prongs that come out of the alternator and I did it about four or five times. And then rinsed it all off and connected it up to the new or new used alternator, and believe it or not it seems to have solved all the problems. Just telling you this so you can know for your future because I guess the six-cylinder Subarus can be a pain.

I'm glad you were able to solve your problem, but what you did can only be described as a "cargo cult" repair.  Baking soda does not contain electrical repair magic.  It's used to clean BATTERY contacts because batteries contain acid, and the acid creeps out to the post and causes corrosion.

There is no acid in an alternator (H4 or H6), and thus no acid to neutralize with an alkali such as sodium bicarbonate.  You might as well have cleaned that connector with snot, because it was probably the act of cleaning the toothpaste out of it that restored the contact's functionality.  Granted, baking soda toothpaste is probably a little more abrasive than non-baking soda types, so that may have helped, but that still doesn't make it appropriate for this application, any more than it would be for relighting a burned-out headlight.

Go get a can of electronic contact/control cleaner/lube.  In a pinch even brake cleaner is okay, because the combination of aerosol spray and degreaser will help free up crap from the contacts and not leave residue.

Edited September 20, 2022 by jonathan909