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2002 Forester
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Discussion Starter #1
I looked at a friend's 2002 Forester that had an unknown electrical issue that caused the car to die. I jumpstarted the car, and it started, but the battery voltage while running was very low, about 11.5V. It was about 11.8V with the car off.

The problem started soon after the car got hit in the front left corner. It's not serious, the fender is just a little crumpled. I'm not sure if this is just a coincidence, but when I saw that the battery is positioned in that corner under the hood, I was worried that the battery might have gotten damaged internally, so I swapped in another known good battery. It still didn't charge. The running voltage was about 12V, with the car off it was a little over 12V. So, I think the problem starting soon after the car got hit is just a coincidence.

Anyway, is there anything else I should check before replacing the alternator? From what I can see in the wiring diagram, this charging system is pretty old school. It doesn't seem to be controlled by the engine ECU or anything like that. So I can't really think of anything else that should cause it not to charge aside from a bad alternator. The accessory belt looks fine and it's spinning the alternator, but it's just not charging. Should I go ahead with replacing the alternator, or is there anything else I should check? I plan to make sure the fuses are good that go to the alternator, but otherwise I think it's probably a bad alternator. Also, I didn't think to check whether or not the battery light is on in the cluster. So, I'm not sure if it is or not. Thanks.
 

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2007 Forester Sports XT 4EAT
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@Justhere4thewiringdiagram I see this is your first forum post, so welcome to the forum from Oregon! :biggrin:

The grounds can be problematic on the earlier models, so that might be a place to start the troubleshooting.

If you suspect the battery, most auto parts stores will check the battery & alternator for free. :wink:

Yes, the charging circuit is pretty simple. The voltage regulator is built into the alternator. The regulator senses the battery charge voltage thru pin [2] in the alternator connector. This sense lead is fused in the engine compartment fuse box, fuse #3.

Also...
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Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 
2002 Forester
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9 Posts
Discussion Starter #3
Thanks, like I said initially I was a little worried that the battery had a shorted cell that might be dragging down the voltage even if the alternator was charging ok, but after putting a battery in the car out of another vehicle, the voltage was still only about 12V when running. So, probably not a battery.

It was kind of weird that after jumping the car and only letting it run for a minute or so, I was able to shut the car off and it cranked itself over and started under its own power, even though the car had been setting in one spot (in the cold, this is in Michigan) for a couple weeks. I didn't even try to start the car under its own power before I jumped it. I just assumed the battery would have been dead. I've also never really seen a car start by itself when the battery voltage is only about 11.8V when the car is off. So again, I'm a little suspect of the battery, but it's still not charging even with another known good battery installed. Also the battery that's in it has a manufacture date of December 2017, so it might still be good, just discharged.

If the grounds are known to be bad, couldn't I check the voltage between the alternator positive terminal and the case of the alternator? This should check the voltage right at the alternator itself, eliminating the possibility of a bad battery ground throwing off my reading at the battery. Although I guess a bad battery or engine ground might throw off the voltage on the sense circuit at the alternator, so still probably worth looking at the grounds.
 

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2007 Forester Sports XT 4EAT
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The ground for the alternator is thru the alternator frame to the engine block. Check that the alternator frame to the engine block reads close to zero ohms. If not, the pivot bolt could be loose or there's too much aluminum oxidation that may need to be cleaned off. :confused:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 
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2017 Forester XT Touring CVT
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@Justhere4thewiringdiagram I see this is your first forum post, so welcome to the forum from Oregon! :biggrin:

The grounds can be problematic on the earlier models, so that might be a place to start the troubleshooting.

If you suspect the battery, most auto parts stores will check the battery & alternator for free. :wink:

Yes, the charging circuit is pretty simple. The voltage regulator is built into the alternator. The regulator senses the battery charge voltage thru pin [2] in the alternator connector. This sense lead is fused in the engine compartment fuse box, fuse #3.

Also...

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
The ground for the alternator is thru the alternator frame to the engine block. Check that the alternator frame to the engine block reads close to zero ohms. If not, the pivot bolt could be loose or there's too much aluminum oxidation that may need to be cleaned off. :confused:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
excellent advice!!!!

I looked at a friend's 2002 Forester that had an unknown electrical issue that caused the car to die. I jumpstarted the car, and it started, but the battery voltage while running was very low, about 11.5V. It was about 11.8V with the car off.

The problem started soon after the car got hit in the front left corner. It's not serious, the fender is just a little crumpled. I'm not sure if this is just a coincidence, but when I saw that the battery is positioned in that corner under the hood, I was worried that the battery might have gotten damaged internally, so I swapped in another known good battery. It still didn't charge. The running voltage was about 12V, with the car off it was a little over 12V. So, I think the problem starting soon after the car got hit is just a coincidence.

Anyway, is there anything else I should check before replacing the alternator? From what I can see in the wiring diagram, this charging system is pretty old school. It doesn't seem to be controlled by the engine ECU or anything like that. So I can't really think of anything else that should cause it not to charge aside from a bad alternator. The accessory belt looks fine and it's spinning the alternator, but it's just not charging. Should I go ahead with replacing the alternator, or is there anything else I should check? I plan to make sure the fuses are good that go to the alternator, but otherwise I think it's probably a bad alternator. Also, I didn't think to check whether or not the battery light is on in the cluster. So, I'm not sure if it is or not. Thanks.

just to add something i once had this problem with my 01 forester. i changed the battery since it was old. still had issue, so i had alternator tested. still had problem so it be safe i threw in an alternator. still had problem.

while checking my work i realized that the wiring harness connector for the voltage regulator on the alternator actually had one of the wires leading in to the connector broken off.

i cut out the old connector and soldered in a new connector and wires for the voltage regulator.

totally fixed. just sharing my story so that you have another thing to look at.

i felt stupid because of how simple it was.

check all the connections for the alternator for broken wires or damaged insulation.
 
2002 Forester
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9 Posts
Discussion Starter #7
The ground for the alternator is thru the alternator frame to the engine block. Check that the alternator frame to the engine block reads close to zero ohms. If not, the pivot bolt could be loose or there's too much aluminum oxidation that may need to be cleaned off. :confused:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
This ended up being the problem.

I load tested the circuits on the connector at the alternator (FYI, only one of the two circuits, the voltage sensing circuit, load tests properly. The other one barely lights up a test light, but I'm sure this is normal since this is the circuit that turns on the indicator in the cluster.

Since both circuits seemed good, I was just about to call the alternator bad. But just to be sure, I clamped one end of a jumper cable to the case of the alternator, and the other end to the negative terminal of the battery. Sure enough, the battery voltage jumped right up to something close to a normal charging voltage. You could noticeably hear the change in the way the engine ran like this. I thought maybe the engine ground cable was bad, so then I clamped the jumper cable elsewhere on the engine. The alternator didn't charge like it did when I clamped it right to the case of the alternator, so I can only assume that the alternator mounting points had gotten enough corrosion on them that the alternator didn't have a good ground to the engine any more.

Just to be sure, and since it was a little corroded, I still replaced the engine ground cable, but then I took the alternator off. There was a pretty good amount of white aluminum corrosion at all of the mounting points on the engine.

The car has almost 200k miles on it, so I decided to just go ahead and replace the alternator while I had it off, even though I'm pretty sure the alternator itself was still ok. I could hear the bearings squeaking a little bit when I spun the alternator, so I figured it wasn't worth putting a 200,000 mile alternator back on the car.

After thoroughly cleaning off all of the mounting points on the engine with sandpaper and a wire brush, and installing the new alternator, the car is charging at a solid 14.4V. :icon_cool:
 
2002 Forester
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9 Posts
Discussion Starter #9
I was actually pretty surprised that it was possible for something physically bolted to the engine to have such a bad electrical connection to it, but I really think this was it. I've never seen a bad ground between an alternator and an engine like this.

I replaced the engine ground first, and just out of curiosity I checked to see if it was charging, and it wasn't. It didn't charge until I actually removed the alternator and cleaned its mounting points. Now, granted I replaced the alternator as well, but I was able to get the old one to still charge if I clamped a jumper cable to the alternator case and the negative battery terminal.
 

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2007 Forester Sports XT 4EAT
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The grounding is known is be deficient on the earlier models. We ran extra ground wires on both our Forester, the alternator frame being one of the added grounds.
+1 on deficient grounding - clearly an issue on my 2005 FX and 2006 FXT. But by 2012 someone at Subaru had received THE WORD. There are ground straps everywhere - really a big improvement in this one area my my 2012 FXT.
 
2002 Forester
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Discussion Starter #12
Right, but again, this was not a problem with the ground cables themselves. This was just that the alternator mounting points themselves were too corroded to allow the alternator to conduct electricity between it and the engine block. Clamping a grounded jumper cable to the engine did nothing. Clamping it right to the alternator corrected the issue. I'm just surprised alternator mounting points can get that corroded. They didn't look THAT bad, but I guess it was enough.
 

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Aluminum oxidation appears more on engines when the vehicle is parked outside & not in a garage. The oxidation will be much worse if you live in a State that salt the roads in the winter. :icon_eek:

If your alternator was oxidized enough to prevent a good connection, then one has to assume your other ground connections could be suspect, as the factory doesn't coat the connections with a grease, they're just screwed or bolted on.

We've gone thru most of our ground connections. Remove, clean, grease & reattach. Easy to do, as you happen across them. I'd start with the ground connections that are subject to road spray. :wink:

I've used Kopr-Shield, which is conductive, is also very messy! I've since switched to No-Ox-Id "A" or No.2-EJC (electrical joint compound). You can also use dielectric grease, but it's a very lightweight grease.

You don't need the grease to be conductive, it's to keep the moisture & air from the connection, which will prevent any corrosion. I lightly coat the parts to be connected together & the process of tightening the screw (or nut) will squeeze out the excess grease making a sealed bonding point. This process also works on the battery terminal connections & I can say I've never had any corrosion on our batteries.

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 
2002 Forester
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Discussion Starter #14
Good advice. Where are the other major grounds on this car? I saw the one running from the battery directly to the frame in front of it a few inches forward, and I cleaned that. Seems like there's another one that runs to the transmission? I didn't see that one, but I didn't look around too much. I also cleaned up one that seemed to go to the ABS module in the front right corner under the hood.
 

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2007 Forester Sports XT 4EAT
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There are lots of grounds! The ones that come to mind: :confused:

• The main battery to engine ground is near the starter, it a heavy cable directly from the battery.
• There's the battery to frame connection near the battery.
• There a ground on the firewall to the engine near the pitch stop.
• There a bunch of critical grounds on the intake manifold.
• There are ground near the strut towers (both sides) to the engine.
• There are grounds, either side, towards the front, low on the frame.

There are many more, as there's 3 pages of grounding points in the '99-'02 Subaru Technical service documents. The '03-'04 ground distribution has 11 pages! :icon_eek:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 
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