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I have an 06 Impala LS with only 35 thousand miles. The car is like new. It is a one owner car that was kept in a carport with a cover over it most of the time. It sat in the carport for three years without being started. After I bought it I installed a new battery and everything was working fine but now the charging system message has come on the dash. I tested the alternator output and it showed 11 volts. The battery died so I charged it overnight. Next day the message is gone and the alternator shows 14.3 output. I drove the car a couple of miles and the message came back on the dash. Checked the alternator and it showed 11 volt output. Hope someone can help me get this solved. New member. Thanks
 

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I have an 06 Impala LS with only 35 thousand miles. The car is like new. It is a one owner car that was kept in a carport with a cover over it most of the time. It sat in the carport for three years without being started. After I bought it I installed a new battery and everything was working fine but now the charging system message has come on the dash. I tested the alternator output and it showed 11 volts. The battery died so I charged it overnight. Next day the message is gone and the alternator shows 14.3 output. I drove the car a couple of miles and the message came back on the dash. Checked the alternator and it showed 11 volt output. Hope someone can help me get this solved. New member. Thanks
You are measuring the voltage at the alternator, but not really testing it. I'm thinking the alternator is bad and not charging the battery, hence the voltage drop from 14.3 to 11 volts after "a couple of miles" of driving on the new battery.

To verify it's the alternator, you can remove it and get it tested at Autozone (and other parts stores). Also, you may need to re-charge the battery to get the car started once the new alternator is installed. If the engine does crank and fire with the available 11 volts, the new alternator will re-charge it. Otherwise, you'll need to get a charger on it.

HTH.

Doug

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Thanks for your reply. I found this on the internet. Technical service bulletin for 06 Impala. The bulletin requires reprogramming the body control module with updated software. Says take it to a dealer for reprogramming and it will solve the problem Are you familiar with this tech service bulletin?
 

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Thanks for your reply. I found this on the internet. Technical service bulletin for 06 Impala. The bulletin requires reprogramming the body control module with updated software. Says take it to a dealer for reprogramming and it will solve the problem Are you familiar with this tech service bulletin?
Maybe you can post the TSB?

Looking at the drawing (attached) for the charging system, the BCM monitors the charge/discharge current into/out of the battery. In turn, the BCM communicates with the PCM which controls the alternator by varying the duty cycle of the chopped current flowing thru the rotor.

When you measure the voltage at the alternator, you are measuring the battery voltage, since the two are tied together. 11V makes me think the voltage regulator inside the alternator has gone bad and is failing to charge the battery.

Have you tried measuring the voltage with the engine running at idle?

You can try getting the BCM software updated. Not sure what all that entails.

You might inspect the wiring going to the alternator, in particular the two small wires. They control the alternator, and hence can affect the voltage output.

There are ~4 bolts holding the alternator in place. So removing it is not very difficult. (Disconnect the battery first.) You might remove the alternator and get it tested to be sure it's not part of the problem, so you can rule it out, if the problem lies elsewhere.

Doug

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