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BATTERT LIGHT / BRAKE LIGHT after new alternator? Help

 
Old Sep 14, 2018, 08:24 AM
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BATTERT LIGHT / BRAKE LIGHT after new alternator? Help

hey guys, I just picked up an Evo 9 MR. The car has the Brake and Battery light on full time. The last owner told me itís been on Sincd he replaced the alternator and has not gone away. I searched all over as I see the brake and battery light is a common sign that the alternator is bad. The car is charging and from what I can see in the MR volt gauge itís at 14.5. I have checked the fusesble link on the battery and all looks well. Any ideas how to turn these lights off? Is this a possibility of running an aftermarket alternator and the electrical system wanting an OEM? Any info would be greatly appreciated, I donít want to replace a good working alternator unless itís the only way to clear those lights.
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Old Sep 14, 2018, 08:26 AM
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By the way, I apologize for the typos, just stopped off the highway to make this post quickly and did not re-read 🤦🏽*♂️ 😂
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Old Sep 14, 2018, 08:34 AM
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Whats the age of the battery? Curious if its time to replace?

Question, with the Alt light on, does that not throw a CEL? If so, clear any present codes

Wonder if this could be a ground issue?

Anyways, just throwing out some ideas
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Old Sep 14, 2018, 08:56 AM
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14.5v is a little high for a running car. Is it at that voltage at idle too? Does it dip in voltage under load like headlights, defroster, etc.? Is the alternator an OEM or aftermarket/rebuilt unit?
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Old Sep 14, 2018, 09:36 AM
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The MR gauge is not reliable. Get a reading off the battery or alternator post.

I had a pinched wire that reeked havoc on my system after an alternator install.
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Old Sep 14, 2018, 11:16 AM
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Originally Posted by BillAce View Post
14.5v is a little high for a running car. Is it at that voltage at idle too? Does it dip in voltage under load like headlights, defroster, etc.? Is the alternator an OEM or aftermarket/rebuilt unit?
I just watched the gauge (not sure if its accurate or not) and when the headlights/ ac/ and wipers are on it does a dip down to 14v and teeters between 14v-14.5v. I hooked up my snap on scanner from work and tried to see if it showed any faults through a full scan but it shows no codes. I suppose ill try a volt meter later just to double check.
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Old Sep 14, 2018, 01:22 PM
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Originally Posted by MikeyT View Post
I just watched the gauge (not sure if its accurate or not) and when the headlights/ ac/ and wipers are on it does a dip down to 14v and teeters between 14v-14.5v. I hooked up my snap on scanner from work and tried to see if it showed any faults through a full scan but it shows no codes. I suppose ill try a volt meter later just to double check.
My MR gauge showed 14.5 and it was a whopping 16.5v at the battery. Overcharge FTW.
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Old Sep 14, 2018, 02:00 PM
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Originally Posted by Project_Broke View Post
My MR gauge showed 14.5 and it was a whopping 16.5v at the battery. Overcharge FTW.
I wonder if that's what is happening here. Would it make sense that an aftermarket alternator may be overcharging and not regulating like a stock alternator would?
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Old Sep 14, 2018, 02:09 PM
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Like I stated above, mine was due to a pinched wire.
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Old Sep 14, 2018, 02:28 PM
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Originally Posted by Project_Broke View Post
Like I stated above, mine was due to a pinched wire.
which wire ended up being pinched for you? I know it will most likely have no relevance to me but gives me a place to start ha!
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Old Sep 15, 2018, 08:50 AM
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Originally Posted by MikeyT View Post
which wire ended up being pinched for you? I know it will most likely have no relevance to me but gives me a place to start ha!
Voltage reference wire that runs from the battery to the alternator. Basically, the ecu saw 9v instead of 12v due to resistance and bumped the charge.
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Old Sep 17, 2018, 03:55 PM
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I just put my volt meter to the reference wire to the alternator and it seems to be charging at 15v-15.3. I turned on headlights and Ac and it dips down to 12 and then back up to 15v. Is this due to a regulator issue in the aftermarket alternator?
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Old Sep 18, 2018, 11:31 AM
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It is high. So either the regulator, or the reference wire issue like I had would be culprits.
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Old Sep 19, 2018, 09:45 AM
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Thumbs up

[QUOTE=Project_Broke;11839466]
It is high. So either the regulator, or the reference wire issue like I had would be culprits.

ahh okay. Im going to go a bit deeper into it and see whats going on. Thanks for the help Project_Broke! Ill report back with what I find when I do.
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