Question about 2007 Chevrolet Tahoe

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2007 Tahoe alternator not outputting voltage. Alternator diagnostic said it was good and I have a new battery (had to buy it in order to get home). It wasn't working last night, was working this morning, and now isn't working again. Where do I begin troubleshooting. Is there a fuse in this circuit? Help!?

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Start at the battery and check with a dc volt meter while it is running. A good battery puts out a max of 12.5 volts.... If you have ATLEAST 13.0 volts then your alternator is working, but not at peak efficiency which is more like 14.0 volts. If you detect that it isn't charging the next step is to attach the volt meter directly to the alternator. There should be a "hot wire(s)" meaning it should have a rubber boot over it and usually is red like the wires running to the positive side of the battery. NOT running it should show the same voltage as the battery, with the vehicle running it should be producing above 12.5 volts more like 14 volts. If you DO have that type of voltage (14v) there and not at the battery while it's running then yes the alternator is good and the wiring between the alternator and battery is bad/shorted. Don't be MISLEAD because alternators that are going bad have a tendency to work intermittent. If this is the case don't chance it, REPLACE it

Posted on Oct 12, 2013


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Posted on Jan 02, 2017

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SOURCE: alternator not exciting

Hi ' If you changed the battery and alternator,
Check the voltage at the red wire on the alternator. if there a less than 12 volt.
Check the fuse link, that goes in the starter positive bolt.
If the fuse is bad replace and recheck the charging system.
IF charging normal. good.
If not, che the fuse in the fuse box, "" cluster".
If the fuse is blow out, replace. and check again.

OK. I hope this work for you.

Posted on Jul 06, 2008

  • 80339 Answers

SOURCE: Alternator

Yes it is the wire that comes from the alternator/battery lite in the dash.

Posted on Oct 29, 2008

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SOURCE: car battery problem

The alternator test will likely indicate a charging problem from the alternator that is not keeping the battery charged up.
Regardless of the alternator test, it would be best to do an electrical draw test to determine whether there is an excess drain on the battery. This can be done with an ammeter between the positive terminal and the positive battery post. This test is done with key off, all accessories off, no lights on, etc. There will be a small draw on the battery in all newer vehicles, but it should be in the order of up to 50 milliamps. If you are getting more than 200 milliamps of current draw then there is a problem with an electrical system that will drain the battery over a period of days or weeks. Once you know this is true, the electrical systems can be methodically tested.

Posted on Jan 19, 2009

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2nd newly rebuilt alternator burning out.

Due to the nature of the battery technology used with vehicles the alternator is mostly incapable of charging the battery. The car alternator is designed to keep a fully charged battery fully charged and to provide all the power for the car equipment.

The alternator charge rate is regulated by a voltage regulator. Because the alternator output is connected to the battery, the alternator and battery voltage will be the same and the voltage regulator monitors that voltage.

The lower the battery voltage the more output the alternator will produce in order to correct the situation but because a lead acid battery has a high internal resistance to accepting a charge the terminal voltage will quickly rise to the alternator regulated voltage and fool the alternator into thinking the battery is fully charged when the output will drop to the order of just a couple of amps.

Switch on the headlights or a similar load that will lower the battery voltage and the alternator will increase it's output again - but only by the amount of current the headlamps or other load is consuming.
It matters not what the alternator rated maximum output is, it is designed to provide only the necessary current and no more.

The only time an alternator should ever need to produce maximum output is when on a dedicated testbed and then only for a short duration to avoid damaging the unit. Testing the current output on a modern vehicle is not recommended except for the regulated voltage testing and a rule-of-thumb output test where all equipment is switched on and the engine speed raised while the battery voltage is monitored.

Most modern alternators use an internal voltage regulator but a few systems use a separate voltage regulator. No alternator rebuild would be complete without a regulator test and probably a new or replacement regulator, which is where the majority of charging system problems are, or the brush gear.
Assuming the wiring is ok, no alternator should suffer any harm if the voltage regulator and auxilliary diodes (if fitted) are in good order though fitting a defective or a discharged battery can cause it to overheat and be damaged.

The alternator usually just about stops producing an output when the battery voltage is in the region of 14.5/14.8 volts.
Your description indicates the voltage regulator is not working correctly - unless 40 amps was being consumed by the car equipment the alternator should not have been producing 40 amps.. I suggest you also have your battery tested

May 12, 2017 | 1988 Acura Legend

1 Answer

What does it mean when the battery light comes on for my 2001 chevy Tahoe?

Usally it means that the alternator is not charging.Check the voltage coming out of the alternator with the engine running.It should be 13-14.7 volts and if its less than 13 volts or more than 15volts then replace the alternator.If alternator test good then check battery voltage you need at least 12 volts.

Jan 19, 2012 | 2001 Chevrolet Tahoe

1 Answer

96tahoe batterygaugemovesfrom10to14 the battery is new

14 is good, (10 is bad). Any other issues with the electrical system?
The gauge may just be off a little. If you put a voltmeter on the battery with engine running, it should show anywhere from about 13.5-14.5 volts. That's the alternator output to charge the battery and run the car's electrical systems.
If voltage truly dropped to 10 volts when car was running, I think your check engine light would come on, and there would be serious issues with lights flickering and dimming. Check the alternator output. Good luck.

Dec 04, 2011 | 1996 Chevrolet Tahoe

1 Answer

Replaced alternator and battery in 2002 Chevy Tahoe. Battery voltage remains between 9 and 14 (leaning more towards 9 and at times falling completely until trucks shuts off)

When you say battery voltage how are you testing it? Are you looking at a gauge on the dash? Or are you physically testing it with a multi meter? If the truck is dying and you recently replaced the alternator and battery I would first suggest you to check all them connections again real good. Snug them all up. Check for corrosion and clean as needed. Did you replace the battery and alternator with new/re-manufactured battery and alternator? The alternator needs to put out at least 13.6 volts to charge your 12 volt battery or the battery will not maintain a charge. However the alternator runs the vehicle once it is started. The battery is used only to start the car and then the alternator runs it. So if your vehicle starts and runs and then dies you may have a bad alternator. Check your connections first and then test the alternator with a multi meter. Anything less than 13.6 volt will not suffice. 14+ volts would be the hopeful output of a good alternator.
regards, Tony

Apr 12, 2011 | 2002 Chevrolet Tahoe

1 Answer

2007 Chevy Tahoe - noticed headlight flicker then shortly thereafter vehicle will not start. Have checked the battery and alternator both are fine. When trying to start there is a clicking noise that...

Either the alternator is not charging the battery or you have a draw that is draining the battery. The alternator must have power to the field coil and a good connection from the charge terminal to the battery in order to charge. You can confirm the batrery is charging by checking the voltage at the battery with the engine running. Voltage should be at least 13.5vdc. If yes, see dead battery section at link below.
Do It Yourself Diagnosis and Repair

Aug 10, 2017 | 2007 Chevrolet Tahoe

2 Answers

Battery light is on belts are good not charging what could it be?

Battery light is directly connected to the voltage regulator of the alternator. If it is on, it means you have a bad alternator/regulator combination meaning a new alternator is in order.

This is a very common problem. That's why they have a light for it.

Wish you luck on this one.

Jul 02, 2010 | 1997 GMC Sierra

1 Answer

Need to know what p0622 and p2503 diagnostic codes are. is this my battery? this is on an 2005 grand caravan

Sounds more like an alternator problem. Check output voltage of alternator, code P2503 indicates low voltage. Check/clean all connections at battery and alternator, as well as check all fuses/relays under hood in fuse relay box, just in case fuse blown as well. If all checks out good, you may need a new alternator.

Dec 20, 2009 | 2005 Dodge Caravan

1 Answer

Alternator good,no output battery volts 11.5

How do you know the alternator is good? If it has no's bad. Are you checking alternator voltage output at battery? You want to check voltage it at the alternator if you can acces it.....bad wires could be to blame. Check all wires from aternator, to starter, to battery. If they look anything but new, I would replace all. Have Autozone or Advanced auto do a test on the battery, they will tell you if it meets CCA (cold cranking amps) set by the Ford, both under a load and not under load.

Nov 25, 2009 | 2002 Ford E250

1 Answer

New battery when i turn on the heat. my battery light came on? why

The alternator should be tested for its operational value in this case. There may be some issues with the charge rate.

Testing the amperage output of the alternator is good for measuring the amount (not the level) of voltage the alternator can produce. This test can be tricky because if the alternator is weak it can still show it as producing amperage. Which is good, but if the voltage is low, it will still allow the battery to go dead. To check the amperage output of an alternator an amp meter is needed. Once the meter is connected start the engine. Next turn on all electrical accessories and raise the engine idle to about 1200 RPM. The alternator should output the max amperage it was designed to produce. Example: a 90 amp alternator should output about 88 amps. Note: An alternator cannot sustain maximum output for long periods of time. If the alternator is forced to operate at maximum output it will overheat and fail. An alternator is designed to operate at max amperage output only for a reasonable amount of time.

((Connect the voltage meter lead the same way you would in a battery static voltage check, Start engine (do not drive) at engine idle the voltage should be between 13.6 to 14.3 volts. If not the alternator may need replacing.)))

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1 Answer

Just installed a new alternater and the battery gadge is reding discharge I had the battery checked and its good. Can you help

Check the 'Bat' / 'Charge'/ 'Alt' indicator on the dash panel lights when the vehicle ignition is switched on prior to starting the engine.
This indicator should extinguish within approx 1 second of starting engine.

If the indicator is not operating the alternator cannot provide charge current - check:-
1) the wiring connections to the new alternator,
2) the indicator lamp is not blown,
3) the alternator is properly grounded.

If the indicator light works normally, check the output voltage of the alternator is approx 14.5v when the motor is running.
If its about 14.5v, the battery should be charging.

Aug 12, 2009 | 2003 Chevrolet Tahoe

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