Question about 2002 Chevrolet Silverado 2500HD

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The voltage needle is bouncing. The batteries have been checked. The alternator has been checked. They are all good, any ideas? Thanks for any help.

Has new alternator, serpentine belt, idler pulley, battery cables have been cleaned. Started truck, disconnected batteries and truck continued running. The tension arm is bouncing a little and the idle of the motor reflects the bounce.

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  • Chevrolet Master
  • 15,628 Answers

This could be from current sensing from the voltage regulator. Get another meter and hook it up and see if it bounces. If it does, there is nothing to worry about. If it does not, the dash gage panel needs to be reworked.

Posted on Dec 01, 2014


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SOURCE: insalation of serpentine belt 98 chevy cavelier

Here are instructions and routings for belts hope this helps.

Posted on Dec 15, 2008

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SOURCE: flashing dash lights and gauges

Your Body Control Module could be going bad.

Posted on Mar 19, 2009

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SOURCE: 2008 Chevrolet Aveo5-Serpentine belt change

Stick a 1/2 inch ratchet or breaker bar into the square slot in the arm and turn.

Posted on May 16, 2009

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SOURCE: severe whistling noise at idle,acceleration.

Have the codes read to see if they are related. Make sure the belt is the correct length. Inspect the pulleys and bearings for failure, also you can look at the entire system an see if there is an alignment issue.

Posted on May 31, 2009

  • 1776 Answers

SOURCE: 2003 Chevy Suburban, Alternator failed,

I would look for a short in the output wiring at the alternator. My nephew had an intermittent charging problem and I took the car to an autoparts store and had them check the alternator output. Most parts stores will do the check for free. Anyway, while it was hooked up and the output was being checked, I fiddled with some of the wires at the alternator to see if it had any effect. It did. I noticed that as I moved the wires around, the output changed. I was able to isolate the problem to a wire that ran inside the plug. I resoldered the wire and that fixed the problem. I'm not saying that your problem is the same, but I would definitely look at a wiring short somewhere. I sympathize, since there is nothing more aggravating than finding the source of some electrical issues. Anyway, I hope this helped and that you find a resolution to your problem. Best wishes.

Posted on Aug 28, 2009

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Have to jump it off alot, battery good,replaced alternator 1 month ago, now doing it again. tested at auto zone, said starter bad. tested at toyota, said starter working fine. Any suggestions?

Steven, Check for loose/slipping belt (tensioner) may not be working as it should, look for loose connections on battery and alternator.
If you had a digital volt meter, it could help diagnose problem much easier, lets say your car fails to crank, with headlights on, you can put the meter on the battery terminals and battery voltage is around 11.7V and bounce back to 12.2V or higher when lights are off, that would some what tell you the starter is defective and battery OK.
With car running the voltage should show approx, 14.0 V. or more which tells you the alternator is working OK.
If battery is checked when car is not running and falls below 12 volts the battery is weak and bound to fail. Ideally a good battery is 12.4 to 12.6 V. See links below for more helpful info. and test methods.
Charging System test multimeter
How To Check Charging System EricTheCarGuy
How to Test Car Battery with Multimeter

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1 Answer

What would cause the battery gauge on a 93 jeep grand Cherokee Laredo to bounce between 14v and 9v. this is also running the battery dead and not charging the battery back up.

Several things need to be checked before an accurate diagnosis can be made, however in general it is most likely your alternator going out OR a bad connection in your alternator/charging circuit wiring.

It's also important to test/verify that you have a good fully charged battery (with no dead cells) before any tests of the charging system. An alternator needs ample battery power into it before it can produce good charging voltage and amps out of it and back into the battery.

If you test the voltage directly out of the alternator's output post/connector (with the output wire disconnected), you will be reading direct alternator voltage output, which should be approx 13.5 to 14 volts, steady. If the voltage is at ~14 volts, then suddenly cycles down to 9 volts (or anything less than 12 volts), then you have a defective alternator.
If the alternator, while isolated, tests out at a constant 13.5 to 14 volts, then the problem is most likely a bad wire or connection in the charging circuit wiring.

There is also the possibility of the battery (how old is it?) shorting out internally, causing the voltage fluctuation. That's why I previously said you need to verify each battery cell is fully charged and good. You can usually test this with a battery hydrometer (if it's not a "sealed" maintenance free battery).

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Needles on my Gauges are absolutely crazy! 1996 Pontiac Grand Am SE V6

1= this happen because th IVR fail, see the diagram and test it use the DVOM OR VOM for test the IC .l
2= test the thermistor or sensor for defective.
3= if the voltage of IVR is out of regulation in this case +12vdc,test for ground.if is o.k test by the side of battery side of the IVR, if this voltage is present replace the IVR, if regulated voltage is withing specifications, test the printed circuite from the IVR to the gaues, and if there are open circuite replace the circuit board. OF course test the fuse too.
God bless you


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It sounds like a faulty voltage regulator, faulty alternator, or a bad ground. Try checking the voltage output with a voltmeter, preferably an analog (needle) type. If the needle is "bouncing" then the output of the alternator is not "steady". This voltage variation, if severe enough, could cause your electronic meters (such as your speedometer) to perform erratically.

Also, if you have performed any aftermarket modifications to the electrical system (such as high power stereo installs, etc), temporarily disconnect these and see if the problem resolves. A stock alternator for this car only puts out around 70-80 amps. It doesn't leave much of a margin for additional current draw from high power add-ons.

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