Average alternator voltage range on a 2008 trailblazer/?

Sounds like the the alternator go surged or shorted, probably burned out the regulator inside the alternator. Remove the alternator and have it bench tested at the parts store, you may have damaged the battery also, you may want to take it with you and have the parts store load test it.

Dirty battery terminals
Loose battery terminals
Bad alternator
Bad starter
Glove box light stays on, even when closed

Keeping it short and simple. Check your battery voltage, looking for about 12.4 vdc with the vehicle not running, about 14.3 vdc with the engine running. It sounds like you may have a bad alternator. Depending on what your voltage readings are will determine what's going on. Do you have to jump the battery to start it again? If you jump it and can start it. Then take the jumper cables off and can't start it then your battery is bad because it won't hold a charge. If you can start it without a jump and it just dies that would most probably be an alternator. Keep it simple to start, first battery then alternator. Beyond that you may have a way bigger electrical issue.

you have something pulling power from the battery or I would suspect the altenator

Have u ever went on the internet about your car.there may have been a recall on your alternator or other people with the same trouble your having.I had a mercury that I to replace the alternator three times.Come to find out there was a recall on my alternator because of how It sat in the engine.the wires running to it kept getting burned out by the powersteering belt.Just a thought when u keep replacing the same part.

Could be battery,alternator works you said is OK.Looks battery is five years old.

Many batteries may only last around three years. Check battery voltage at rest before starting. Any voltage in the low 12v range may be a sign of a faulty battery.If low voltage present, then perform a parasitic drain test:1) Disconnect battery POSITIVE terminal and connect ammeter in series, between battery positive terminal and positive lead.
DO NOT START THE VEHICLE!!

2) With all vehicle doors closed, alarm off, lights off, radio off, and all other accessories off, wait for around 20 minutes and then read the ammeter. A healthy system should read about 0.03 amps and little more. If reading more, then the vehicle could be suffering a parasitic amp drain, and you will need to locate this issue.


3) Reconnect battery when finished.


If no major parasitic drain present, yet low battery voltage then:


4) With vehicle started, check the voltage charge from the alternator. Connect voltmeter to battery terminals and take reading. A healthy system should be charging in the range of 14volts or down to around 13.5 volts. If reading around 12 volts only, then check and replace alternator.

check voltage from battery car running. if alternator good it will produce 13.6-14.2 volts. if lower replace alternator. good-day ! make sure battery posts and wires are clean and tight.

Sounds more like the Alternator or Voltage regulator is not charging the battery correctly. Have the Alternator checked. If you remove it and take it to Auto Zone or Advance Auto they should be able to test it for you.

Possible battery drain.
Remove the negative battery cable from its post and connect an ammeter red probe
to the negative battery post and the black probe to the negative battery cable.
Now start pulling fuses until the voltage on the meter returns to normal.
(anything above a half of a volt is too high) The fuse you pulled to get this
result is the affected circuit. Now you have to probe it from its B+ source to
the load
to find the short. Check all connectors for rust and the line for opens or
shorting to ground. Repair accordingly.