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familyguy9877

Cobalt alt only charges sometimes....

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I have a 2006 cobalt with the 2.2 ecotec, stock alt, but the vehicle only charges sometimes. Voltage will fluctuate between 12.4 and sometimes up to 15.2 while the engine is running (normally when charging it stays around it’s regulated 14.4-14.6). Not rapidly, just sometimes it’s charging then it’s like a switch is flipped and then it’s not then back to charging a while later and so on. Very frustrating because when it’s charging it keeps good voltage (13.7+) full tilt but when it stops charging I’m dipping to like 12.0-12.2. Question is, is this a fuel economy feature or a fault somewhere? It could be a faulty alt because I’m pretty sure it’s the original with 251k on it but I’d think if the alt was bad it would just not work at all, not sometimes work sometimes not. If this is some stupid feature that the car computer is controlling when charging occurs how do I bypass that??

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wife had alero same motor never had problems but no system either.. go to advance ask them to do load test on alt/batt.. maybe alt just needs replaced maybe belt or pulley tensioner.. u may need alt or just a agm batt and big 3 wires under hood..


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Boomin_tahoe said:
2 ohms rule

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You have a pcm controlled alternator. The voltage you are describing is normal. Depending on your exact vehicle, you may be able to get a bypass module to fix your problem. Or it may be as simple as unplugging the voltage sensor wire at the battery.

 

GM Modules


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I just recently fixed this issue on my Tahoe by replacing the serpintine belt. Just one possibility for ya.


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You have a pcm controlled alternator. The voltage you are describing is normal. Depending on your exact vehicle, you may be able to get a bypass module to fix your problem. Or it may be as simple as unplugging the voltage sensor wire at the battery.

 

GM Modules

 

That website says the PCM controlled alts started after 2006 (the year of my cobalt) from looking at pictures it would appear my car should have the 4 pin plug. I didn’t have time to take the intake out and look for sure though. I have only two agm batts in the vehicle already.

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replace belt check pulleys and get load test done if it test weak replace alt or batt


KENWOOD X301 HU, PRECISION POWER Phantom 1000, FU 750 12, 2.1cfad ported, soundqubed 6.5" coax/doors, hp & lp xover on hu, AGM starting batt...

Boomin_tahoe said:
2 ohms rule

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if the voltage regulator is going bad, depending on the alt, they do act that way. when you rev the motor it's enough to self excite it and thats why it is more of an issue at idle for you

 

verify it's not PCM controlled first, before anything

 

also try posting on your vehicle specific forum


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Your vehicle is pcm controlled and has a battery temp sensor.

 

The ecotec crap in the pcm causes the alt to shutdown during stops and idling when not needed and also will stop charging as much at highway speeds.

 

You need an external regulator to fix the issue.

 

Sent from my SM-N950U using Tapatalk

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if the voltage regulator is going bad, depending on the alt, they do act that way. when you rev the motor it's enough to self excite it and thats why it is more of an issue at idle for you

 

verify it's not PCM controlled first, before anything

 

also try posting on your vehicle specific forum

 

It doesn’t charge half the time even when I’m revving to 3k rpm. It’s like an on off switch

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Your vehicle is pcm controlled and has a battery temp sensor.

 

The ecotec crap in the pcm causes the alt to shutdown during stops and idling when not needed and also will stop charging as much at highway speeds.

 

You need an external regulator to fix the issue.

 

Sent from my SM-N950U using Tapatalk

 

Are there any good external reg you would recommend??

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Are there any good external reg you would recommend??
I’ll try to get a load test done tomorrow
Like your saying do all the basic checks like getting your battery tested and alternator tested for working condition.

 

If all is good then move on to the normal bluebox external regulator you find in car audio applications.

 

The mainstream use of it is in limosines, theres only one available aside from all the chinese knockoffs.

 

Also alternator companies like mechman,singer,ces, etc.. all provide a pcm bypass solution for gm vehicles now.

 

Sent from my SM-N950U using Tapatalk

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