Question about 2008 Chevrolet Avalanche

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14.5 volts after you start it after about 5 miles it drops to about 12.7 stays there till you restart it replace alt and alt module on the neg. battery cable still has the same problem

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  • kiphansen May 21, 2009

    voltage was checked at the battery and the alt thanks for looking

  • Moe May 11, 2010

    Does this charging problem end up as you need to get a boost or is it a problem with the gauge. ? Is this problem giving you a no start ? When you say 14.5 volts and then 12.7 volts do you mean as this is checked with a voltmeter at the battery or this is the indication on the dash ?



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My 08 Av. does the same thing. I checked on mine and found that allegedly they somehow have the ability built into them to turn the alt. down when you get going and your batt. is charged up so the drag that the alt. pulls on the engine is cut back to help with gas mileage.

Posted on Jul 07, 2009

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It sounds to me like you should prepair to buy a new battery. A question I have for you is,"Do you have a lot of electronics,ie;mega watt sterio,vidio equipment,ect.? If you have a lot of electronics you will need a higher amp altinator to keep thing under control. If the battery is 3 or more year old, I would have it checked. The alternator is doing it's job.

Posted on May 21, 2009


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Is there problems with these alternators?

No it dosn't sound like its the ALT.
You need to check the output alt .Take a volt meter with the vehicle running and the meter set to 20 volts DC black to black red to red on the battery you should 14 to 16 volts 12 or under is no good.
If your ok with voltage shut off vehicle disconnect the NEG terimanl from the battery . Meter on same scale check the battery voltage its a 12 volt battery so it should 12 volts but you say its new .
The problem you may be haveing is a short someware in the vehicle.
You can test for this with the meter on same scale by leaving the NEG cable off the battery vehicle not running red to red black to ground on engine or know good ground under the hood . If you read voltage you have a short some ware in the vehicle and it depends how much voltage you read 1 volt its something small like a switch or something that dosn't draw a lot of AMPS .If its like 5 volts or more then its like a motor something that needs a lot of juice to opperate starting motor window motor seat motor check the connectors to them first its the easyest thing to look at also check the fuse box I have mis labeled fuses that should be 10amp but dont burn out and the wires start to melt .
These are not easy problems to figure and tend to be expensive to have someone else fix so the more you can figure out the more money you will save
Good luck

Mar 10, 2015 | 2003 Ford Focus


Voltage draw down found!
1) repaced bad battery
2) rechecked voltage draw...

Voltage draw down found!
1) repaced bad battery
2) rechecked voltage draw still showing 12 volt drain with all under hood fuses, relays, and interior fuses and relays pulled.
3) Computer was the 12 Volt drain, & had to reprogram itself.
4) gave the new battery a good long charge, reinstalled the battery into the vehicle.
5) Hooked the battery up, pulled the keys out of the ignition, close and lock all doors with auto door lock. Waited minimum of 20 min so the computer would go back into the sleep mode.
6) after 20 minute wait, rechecked the voltage draw by removing the neg battery cable from the battery, hooking volt meter + lead to battery cable end, and neg lead to battery neg post, nothing showing or zero reading.
7) Hooked the neg cable up to battery, started the truck and let the engine idle to normal run temp, then fast idled 1200-1300 rpms for 2 minutes, then drove the vehicle for 5+ miles and alternating speeds. All appears back to normal now. Alt showing 14.2 to 14.4 volts, and no other problems.
After all of the afore mentioned, my problems began with a bad battery cell, thus caused my computer to have the memory reset.Until the computer was reset, I had a 12v continious draw down! I got this info from a repair manual, that I purchase sometime ago. Thanks for your alls help........EJB

on Dec 30, 2011 | 1996 GMC Yukon

1 Answer

My stabilitrak light started going on. I replaced the battery. Today while driving my battery went from 14.6 volts down to 12.5 and then back up. What is going on?

stabilitrac is from balljoints prob on tire rods of sway bar and altonator runs at 14v and batt runs 12. for it to be dropping to 12 you need to run to auto zone n they can check your alt. or while its runnind take your batt post off batt n if it keeps running your alt is good and if it dies out rite away alt has to be changed

Mar 01, 2013 | Cars & Trucks

1 Answer

Charging problem. Have a 97 isuzu rodeo 2wd put new alt and battery in it and when I put a load on the volt meter drops to 12.7. At idle it's on 14 . Why is it doing this?

Because of the load. It will drop in voltage, this is normal. As long as it stays above 12 you will be fine. But just to be sure start the car and turn everything on, then check the voltage. If it stays at 12.7 it's good.

Aug 09, 2011 | 1997 Isuzu Rodeo

3 Answers

Replaced battery. still would not start. Cleaned treminal of all corrision. cranked fine. however 1 day later would not start. jump started . drove a couple of miles but when I turned on lights, engine...

Sounds like a bad alternator. Drained your battery and when you turned on the lights it took all the power left in your battery. When you drain a battery down that far, they are real hard to jump, and coupled with the alternator, the car is not producing enough current to start and stay running.

I would take the alternator off and take it to oyur local auto parts store to be tested. If bad, replace it and charge the battery fully before starting. Then check voltage at battery with motor running. Should be 13.2 -14 Volts DC. If not, you may have a bad battery cable or blown fusible link. (especially that if the alternator tests good).....Mike

Jun 15, 2011 | 1996 Ford Explorer

1 Answer

Hi, i have a triumph spitfire 4 1963 have recently converted it from pos ground to neg ground ,fitted alternator new plugs points condenser ,coil, car runs for aprox 3 miles then splutters to a halt ,after...

It sounds like you have to fit a ballast resistor in the power supply to the coil or get a 12 volt coil. Later spits (-ve earth) used a 9 volt coil with a resistor to drop the battery volts down when running, when starting the full volts are used but the starter will drop this to 9 or 10 anyway, this helped cold starts.)

Jul 07, 2010 | 2006 Triumph Tr 7

2 Answers

1985 dodge powerwagon, lights went dim driving home now wont start, just replaced battery 6 months ago. starter clicked at first then nothing.

The alternator may not be charging the battery. Jump start it, and use a volt meter at the battery, red lead to positive and black to neg. The meter should read between 13 and almost 15 volts, any lower than 13 volts, the alternator is no good. (this is done with vehicle running).

Feb 02, 2010 | 1985 Dodge Pickup 4WD

2 Answers

87 toyota camry new battery wont keep charge, alternator checks okay, in dash bulb for charge and brake and lights stays illuminated?

Generally if charge light is on, alternator has a bad diode in it. This lets the charged battery lose its power by flowing in the reverse direction. It sounds as the alt., is either not connected right or is swtill bad

Jan 18, 2010 | 1995 Toyota Camry

2 Answers

Jeep has been having trouble starting. A new starter, alt, and battery has been tried.

did you replace these things because the engine was turning over slower then normal?
or no turning over at all?
or turning over but wouldn't start?

Nov 27, 2009 | 1998 Jeep Cherokee

1 Answer

Voltage drops after 5 miles

Moe here ,if you check posts let me know I will ckeck back asap.

May 21, 2009 | 2006 Chevrolet Avalanche

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