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2003 Forester Electrical issues - voltage loss? - SOLVED!

8011 Views 11 Replies 4 Participants Last post by  Billgiblet, 
S
Hi all!

I have a 2003 Subaru Forester with 250+k miles :)

I started having an issue starting it, for a while it struggled on and off then eventually it stopped. Boosting allowed the car to run fine.
I had the battery tested, the guy said it was under warranty and swapped it.

That didnt seem to help started once and then needed a boost again, I had checked for any leaks and i dint seem to find any-

I had the alternator tested and the starter tested both came back good- I replaced them both anyways.

So essentially I have now a new starter new alternator and new battery.

The voltage reads at the terminals 12.5 volts while the car is on.

If I read it by the alternator (meaning the positive "nut" to the housing of the alternator) i get 14.6v)

If I read it from the alternator nut to battery (negative) or the starter (ground nut) I get the same reading that the battery has.

Could my issue boil down to not enough juice is being past to the battery? and if so any thoughts on how to find the voltage loss?
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2.5x_sleeper
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I see this is your first forum post, so welcome to the forum from Oregon! :biggrin:

Have you checked for corrosion, loose battery or ground connections? Have you verified the alternator pivot bolt is tight, as that's the grounding point to the engine.

Refer to the wiring diagram below, the wiring from the alternator to battery is pretty simple & easy to trace thru. :wink:

Bobby...

'03-'04

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

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Kevin
G'day & Welcome aboard!

You should definitely be getting 14.6 or thereabouts at the battery when the engine is running. Have you checked the condition of the cables and especially earthing points?

If you connect a jumper lead from the battery negative to the engine (running) what reading do you then get at the battery?
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B
When you say you measure 12.5 across the terminals with the car on, you mean the battery terminals, with the engine running? If so it sounds like the alternator is trying (14.6V) to push current to the battery but it isn't getting there.

My wild guess would be that you have a bad connection to the battery, possibly in the ground legs of the circuit. Leave the negative voltmeter lead connected in one place, like the alternator housing or the negative battery terminal, then walk the positive lead around the system, you'll probably find a voltage difference across a cable or connection where there shouldn't be one. Or just do the right thing and clean ALL the battery cable connections. Winter is coming, and it's no fun to do it out in the cold.
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S
@2.5x_sleeper @Kevin @Billgiblet

Thank you for your suggestions much appreciated!

With the multimeter on the ground terminal I didnt find a voltage drop to any where I tested.
I checked for voltage drop up until the casing of the alternator the screw that mounts through the alternator had no drop.

The alternator did (almost 3v).

Based on the responses I took a jumper from negative on the battery and clamped it to the alternator casing (It made sense to me as it was just giving it a direct ground) it sparked, the car sounded like it was slightly working harder, with that said I was able to get 14+v at the battery terminals.

I am completely confused now :)

Any thoughts?
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2.5x_sleeper
Based on the responses I took a jumper from negative on the battery and clamped it to the alternator casing (It made sense to me as it was just giving it a direct ground) it sparked, the car sounded like it was slightly working harder, with that said I was able to get 14+v at the battery terminals.
Click to expand...
This tells me either the alternator frame is not grounded to the engine OR the battery is not grounded tightly to the engine. Assuming the alternator is tight, that connects it to the engine. Now you need to get from the engine to the battery negative terminal. You could have a poor ground or grounds between the battery negative & the engine.

Assuming the battery clamp is good... those have been thought to be tight to be found corroded! The main ground... battery negative to engine is at the starter. Make sure that connection is tight & free of corrosion.

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
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B
<If> I understand what you just posted, sounds like the alternator has a bad connection to the engine block. If the block showed no voltage drop, but the altn frame did, that sorta has to be the problem. Unusual but not impossible. Try loosening the alternator and working the pivot back up and down, maybe get some anti-seize in that joint.

I was about to replace a slow running wiper motor on my old S-10, started to remove it, and when I cracked the bolt where the ground was made to the firewall, it started working just fine. Grounds can definitely go bad. I see you live in CT, possibly near salt water?
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S
@Billgiblet @2.5x_sleeper

Thank you!

I took out the alternator and took fine sand paper and cleaned the two "brackets" the hold the alternator in place.

Now I am getting 14.6 when the car is on :)

I tested voltage drop from the negative of the battery to the housing of the alternator I was still getting some loss 0.09 to the bracket it was closer to 0.032.

Sounds strange, no?

Would it be beneficial to just ground the housing with a new wire to the battery?

I was able to drive it to work today :)

Thanks again!
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2.5x_sleeper
@samf we ran an extra ground from the alternator to the engine on our Foresters. We actually added several additional grounds to supplement the factory grounding throughout the engine compartment, which is known it be deficient. We figured it couldn't hurt. :icon_eek:

If you live in an area that uses winter road salt, I'd recommend checking the ground connections for tightness & corrosion. Apply dielectric grease when you reassemble the connections for added protection.

It sounds like you resolved your problem, so I'll add "SOLVED!" to your thread title. :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
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Kevin
2.5x_sleeper said:
@samf We actually added several additional grounds to supplement the factory grounding throughout the engine compartment
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Me too!
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S
Thanks! I will do the same :)

Live and learn..
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B
I'll add a postscript. I've been chasing down a recurring P304 misfire code in my 2006. Right after I changed the coil pack a week ago I started having problems starting(cranking without firing, and noticed the voltage was dropping into the 9's while starting. Then found that the battery connections had gone crappy, since when I put the charger clip on, it didn't start drawing heavy current till I touched the actual post. I don't think the battery was getting charged well while the car was running.

Cleaned the battery posts and clamps, then thought about Samf's experience, and loosened the alternator and cleaned the surfaces of the frame and clamps, brushing on some anti-seize, which is basically powdered zinc in grease. The idea is to help exclude water and prevent future corrosion. Then went around and cleaned all the ground connections I could see. Things seems a bit better, and the battery is getting a healthy charge. Don't want to have to do this when it's -10F in January.

Still getting the P304, but that's for another topic. Next stop, injectors.
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