2G Alternator going bad?

[OwenRonn]

My volts seem low and unstable at cruise and warm idle. I checked the belt and it seems pretty tight so I don't think its slipping. Could it be a loose electrical connection somewhere?

 

[dwb]

I'd say yes, bad alternator. Welcome to DSM life. As it heats up it seems to degrade. However, first make sure you verify your battery terminals are clean, tight and secure - same with the chassis grounds especially the starter ground bolt. I'd also verify the electrical connections on the alt are tight.

You could remove it and take it to a parts store and have them test it to see what they see.

 

[DSMPT]

Besides the alternator, there is a possibility that the battery is dead or ECU needs to be repaired or poor ground. You also should check the actual voltage at the battery and the alternator and compare with the voltage in ECMLink when it starts being unstable. Because I see that you have voltage drops below 10v, sometimes even 7v. Shouldn't be below the battery voltage.

 

[OwenRonn]

Besides the alternator, there is a possibility that the battery is dead or ECU needs to be repaired or poor ground. You also should check the actual voltage at the battery and the alternator and compare with the voltage in ECMLink when it starts being unstable. Because I see that you have voltage drops below 10v, sometimes even 7v. Shouldn't be below the battery voltage.

That log was taken with a battery that is almost new and I had O'Reillys check the volts at the battery and they said it was passing, in the low 13v range at idle. I am going to take a look at the grounds before I order a new alternator. Are there any other symptoms that I should look for that would point to bad ecu, it doesn't smell like anything which I heard could be one.

 

[dwb]

Your ecu is probably fine if you're still talking about the charging system, but still always good to check it like Hiroshi said above. IIRC the voltage regulator is integrated with the alternator on a gsx. It's leaking capacitors that sometimes smell like rotting fish.

I'm not sure if a 2g will do this or not, but a failing alternator symptom on my 1g will often start lighting up random dash lights like parking brake and washer fluid.

 

[DSMPT]

That log was taken with a battery that is almost new and I had O'Reillys check the volts at the battery and they said it was passing, in the low 13v range at idle. I am going to take a look at the grounds before I order a new alternator. Are there any other symptoms that I should look for that would point to bad ecu, it doesn't smell like anything which I heard could be one.

My point was, it doesn't matter if the battery was new or not in case if ECU is bad.
Before buying a new alternator, I recommend you to measure "the actual voltage" at the battery and the alternator by a voltmeter and compare with the voltage that is showed in ECMLink stream. It doesn't cost any and doesn't take long.
One of symptoms when ECU goes bad, sometimes ECMLink starts showing the voltage much lower than the actual voltage at the battery. And this starts happening randomly and getting worse by time.
Your log is showing that at some part the voltage drops quickly to 7v ~ 11v from 13.5v. Even if the alternator stopped charging, the voltage shouldn't have gotten that low unless you have some issue else. So I think you should distinguish first if that 7v~11v is real voltage or it's showed only in ECMLink log.
If that voltage drop is real for some reason then ECU is fine. The issue would be something else.

This is one example. Please refer to the link below.

2G - Low voltage in ECMLink but perfect at alt and batt???

So I'm struggling to figure out this issue and can't quite find a thread that describes exactly whats going on with mine. I got my new motor built and dropped in. Now on first startup it was running weird and rough(very rich 10.4) so I checked on ECMLink. In link it was showing 6.4v for the...

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