Inventive1
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I have a 2009 Tahoe. It has the 5.3 engine. It has the largest alternator Chevy used that year. (165 amps?) The following problems have been happening for the last 9 months.
The Tahoe has a problem in the charging system. At times, the charging system will function normally. At other times, it will over charge. I've measured over 17 volts with a multimeter at the battery. At other times, it will essentially stop charging. When this occurs, it will typically measure 12.6 volts at the battery. It has never dropped below 12.6 volts. The gauge on the instrument panel confirms the readings at the battery.
Now the really odd part is that whenever the Tahoe is not charging correctly, turning on the headlights will make the charging system function normally. (Charging at 13.6 to 13.9 volts typically) It does not matter if it is overcharging or undercharging, turning on the headlights, will make it charge normally again.
I tested the charging system according to the test procedure in the Haynes manual. The test was done when only 12.6 volts were measured in the system. According to the test, the alternator was bad.
The alternator was replaced with a New NAPA alternator. (Not rebuilt!) The new alternator has performed exactly like the original alternator! The battery died, so it has also been replaced. (It had a bad cell) I bought the Tahoe about 10 months ago. It had an aftermarket battery in it at that point, so the previous owner changed the battery for some reason.
I took it to a garage to have it diagnosed. The Tahoe performed flawlessly for the mechanic that day! Does anyone have any suggestions on how to diagnose this problem?
The Tahoe has a problem in the charging system. At times, the charging system will function normally. At other times, it will over charge. I've measured over 17 volts with a multimeter at the battery. At other times, it will essentially stop charging. When this occurs, it will typically measure 12.6 volts at the battery. It has never dropped below 12.6 volts. The gauge on the instrument panel confirms the readings at the battery.
Now the really odd part is that whenever the Tahoe is not charging correctly, turning on the headlights will make the charging system function normally. (Charging at 13.6 to 13.9 volts typically) It does not matter if it is overcharging or undercharging, turning on the headlights, will make it charge normally again.
I tested the charging system according to the test procedure in the Haynes manual. The test was done when only 12.6 volts were measured in the system. According to the test, the alternator was bad.
The alternator was replaced with a New NAPA alternator. (Not rebuilt!) The new alternator has performed exactly like the original alternator! The battery died, so it has also been replaced. (It had a bad cell) I bought the Tahoe about 10 months ago. It had an aftermarket battery in it at that point, so the previous owner changed the battery for some reason.
I took it to a garage to have it diagnosed. The Tahoe performed flawlessly for the mechanic that day! Does anyone have any suggestions on how to diagnose this problem?
