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Old 07-31-2016, 05:12 PM   #1
scooby4u
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Default 2015 WRX Charging Fix

Many of you may have noticed the poor charging characteristics of the 2015 and up wrx's. The problem lies in the ECM's ability to control the alternator output to try and achieve better fuel mileage. The result is unfortunately a charging system that allows battery voltage to drop down to 10.1 volts at times.

This low voltage can cause any different issues. Some noted have been poor lighting, accessport rebooting, rebooting of power socket accessories, and much more.

In the video I've posted, I've included visual instruction as well as links to images for electrical system diagrams. Myself and some others have beta tested these systems and data collection and have found no notable negative side affects for allowing the system to operate in this way.

Please note that this is a reference only and performing wiring alteration should be done by someone with proper skill to do so. I do not take responsibility for any damage you may cause to your vehicle.

https://youtu.be/j4Hv4VKvygs
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Old 07-31-2016, 05:56 PM   #2
tank the ek
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I haven't had any issues with this on my car. Interested to hear of others experiences
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Old 07-31-2016, 06:38 PM   #3
absolutezero
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Wow, this totally explains why my AP may have restarted the other day while I was driving. I haven't noticed any other issues with lighting or electronics, and the AP issue only happened once and hasn't happened since. I thought it might have been a connection issue at the port or possibly a short in the wire but I couldn't replicate it restarting. Weird
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Old 07-31-2016, 06:44 PM   #4
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Doesn't it crank up voltage when you turn the headlights on? That is how the newer hondas do it, otherwise it only charges to 12.5v which is all the battery needs and this saves hp and battery life. Connect a voltmeter to the battery with the car running and headlights off and check voltage, then turn the headlights on and check. I'm curious if they run the same type of setup.
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Old 07-31-2016, 07:02 PM   #5
ArmyOfSkittles
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Havent heard of anyone having alternator issues so i guess im here to find iut
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Old 07-31-2016, 07:07 PM   #6
2slofouru
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Something I would do to would be check if the headlight switch sends a simple input to the bcm, cluster, or ecm to trigger higher voltage charging mode. If so, you can install a switch in one of the oem knock out locations that mimics this signal, to crank the voltage. This would of course require a tiny amount of extra hp which would drop mileage a tad. My old impreza has an aftermarket 210a alternator, no switches required.
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Old 07-31-2016, 07:19 PM   #7
scooby4u
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The only time I have found that this system turns off and allows full charging is when the blower motor speed is on full. You can easily monitor battery voltage through the access port. No it does not crank up the voltage with the headlamps on. Please note that the alternator still has its own voltage regulator built in so you will see 12.4 - 14.0 after this fix. This mod eliminates the ecm control over the alternator. I have seen the voltage in the 10.5 range on wot which is dangerous to the injector drive circuits. I have also seen this system over time cause premature failure of ecm injector drive circuits of other vehicles.
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Old 07-31-2016, 07:33 PM   #8
2slofouru
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Quote:
Originally Posted by scooby4u View Post
The only time I have found that this system turns off and allows full charging is when the blower motor speed is on full. You can easily monitor battery voltage through the access port. No it does not crank up the voltage with the headlamps on. Please note that the alternator still has its own voltage regulator built in so you will see 12.4 - 14.0 after this fix. This mod eliminates the ecm control over the alternator. I have seen the voltage in the 10.5 range on wot which is dangerous to the injector drive circuits. I have also seen this system over time cause premature failure of ecm injector drive circuits of other vehicles.
You are saying the ecm controls the alternator yet also that the alternator has its own regulator built in. If this is the case, what triggers the ecm to "allow" the alternator to break free of its bonds and regulate itself?
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Old 07-31-2016, 07:53 PM   #9
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So since watching videos are like torture for me, you appear to be disconnecting the black/red wire that runs from the ECM to the Alternator. I'm assuming this makes the regulator charge at full voltage since it is no longer receiving a signal (fail safe to full power).

This would be the B/R wire on the Alt side and B/Cr on the ECM side.


I guess it's time to hook my scope up and figure out what the signal actually is.
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Old 07-31-2016, 09:19 PM   #10
clark4131
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My AP somewhat regularly reboots, maybe a couple times a month. This would seem to explain it. I'm interested in seeing how this works out...SC
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Old 07-31-2016, 10:15 PM   #11
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2sloforu the alternator can open and close its charging circuit. Most alternators are intelligent in their charging cycles. In this instance the alternator has an override function that the ecm controls.

Sparc, yes you are correct on the wiring. No it doesn't go full charge as that would burn up the battery, but it uses its own voltage regulator. I haven't looks at any terminal reference values but I would assume it's a 5 volt pulse signal control.
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Old 07-31-2016, 10:29 PM   #12
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What input to the ecm initiates its overriding of the alternator's internal control? Would it be a software issue or an external input the ecm monitors?

Quote:
Originally Posted by scooby4u View Post
2sloforu the alternator can open and close its charging circuit. Most alternators are intelligent in their charging cycles. In this instance the alternator has an override function that the ecm controls.

Sparc, yes you are correct on the wiring. No it doesn't go full charge as that would burn up the battery, but it uses its own voltage regulator. I haven't looks at any terminal reference values but I would assume it's a 5 volt pulse signal control.
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Old 07-31-2016, 10:47 PM   #13
gtztdm
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Default 2015 WRX Charging Fix

I would see the dealer about any of this BS or just drive your freaking car. Until it's broke don't f with it.
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Old 08-01-2016, 10:12 AM   #14
scooby4u
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The ecm has a load signal just as they always have. Based on my viewing the ecm is always regulating the voltage in these card unless the blower fan speed is on high then it allows the alternator to charge in normal capacity. This function is there solely for fuel mileage as it allows the alternator to essentially turn off. This is not a programming error. This is mod is mainly for performance gains and people with sound systems that may draw heavily on the battery.
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Old 08-01-2016, 10:39 AM   #15
gosefroba
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I had my alternator replaced at 700 miles.... Had problems starting in the cold. Been 22k miles later and everything is running smooth
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Old 08-02-2016, 11:26 AM   #16
boostingwrx12
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hmmm interesting.. not sure if i should do this mod or not
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Old 08-03-2016, 06:48 PM   #17
lame
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Yo!

anyone try this on a 2016? And know the proper wires to modify?

Cheers!

josh
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Old 08-04-2016, 10:57 PM   #18
2slofouru
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May be a good idea to use warranty if you are having a charging issue...I wouldn't tamper with anything that could void the 36k
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Old 08-07-2016, 02:12 PM   #19
razasharp
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I used to get drop to 10.78 lots of times.. I took the wire out and now it's been 12.86 to 14xx. So far no problem... But I'll keep checking everyday see how cars run. But so car runs smooth..
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Old 08-11-2016, 11:37 PM   #20
-Raven-
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Very interesting! I'll have to try this out for sure!

I regularly put my charger on the battery, and it always takes a while to charge. I put it down to my stereo system draining it, which just runs off a Alpine PDX-V9 amplifier - not that serious at all.....

I haven't checked voltage, and I haven't had an issue with Cobb AP shutting off. But the car does run better with a fully charged battery. Will try this out for sure.
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Old 08-18-2016, 11:34 PM   #21
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I've been testing this out over the last week. Monitoring on the Cobb AP before the wire removal mod, the battery voltage would drop down in the 11's regularly. Now it's constantly near 14.

Now putting my battery on charge with my CTEK battery charger, it goes straight to step 4 (absorption charge mode, basically the charger winding down to float mode) instead of the usual step 3 (bulk charge mode). This quick mod is a certain improvement in my case.
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Old 09-23-2016, 08:13 PM   #22
boostingwrx12
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any more reviews or updates on this mod?
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Old 09-23-2016, 10:29 PM   #23
jlevy
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I did this mod about 2-3 weeks ago and no issues at all since then. Before the mod, I noticed sometimes the windows rolled up more slowly. There didn't seem to be any pattern to it. That's totally gone now. The lights also seem more consistent.

-JL
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Old 09-24-2016, 04:01 AM   #24
jw4902
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This is very interesting, my stock sound system gets louder sometimes on its own as if its getting more power than when I had set the volume. Maybe I was turning the blower fan up to high and that causes it. OP thanks for the info.
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Old 09-24-2016, 07:41 AM   #25
simpleJ
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Wow


My battery has died 2 times in the past few months and now I get no emissions readiness

I wonder if low charge is part of the reason why
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