Tip & How-To about Chevrolet Transformers Alternators Battle Ravage Chevy Corvette


This trick is an easy way to check your alternator to see if it needs to be changed. Most people will test the voltage of the wire with a voltage reader. There is nothing wrong with that and that is the correct way to test an alternator. But, what if you don't have a voltage reader? We all don't own one or have access to one either. No problem. A sign that the alternator is going bad is dimming lights. Whether it is on the dash or your headlights, if you see these lights flickering or dimming, there is a chance that your alternator is going bad. You may want to check for any loose connections in the circuit as well. But for the alternator, this is what you do. Start your vehicle and leave it in park. Go to your battery and take off your hot side post. Be careful when you this and keep the wrench away from anything that can carry a current. When you take it off, make sure it is away from the hot side post or anything that can carry a current. As soon as you take it off, if the alternator is bad, the vehicle will instantly die. If it does this, your alternator is bad or going bad. A weak alternator can still power the car. So, if you want to check and you don't have a voltage reader, this is how you can check. If it stays started and you have been seeing the lights dim, you may have a loose connection with your battery wires.

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I have a 2008 equinox lt n i just bought. A alternater and a new battery. And after a couple of days driving it all the lights on dash comes on and as i'm driving all lights goes off n truck. Slows down n eventually the truck falls dead

the way an alternator works is it has to have what is called a voltage sensing wire, which tells the alternator what level of charge your battery has and how much the alternator needs to put out. If your battery cables are corroded or damaged you can change the battery and alternator every week and the problem will persist. I would start buy checking cables and sensing wire (wire from alternator to battery) and be sure they are free of coorosion and visible damage. if all appears good then do a voltage drop test on battery terminals and cables. also voltage drop test on voltage sensing wire (wire form alternator to battery). this series of test should give you an answer. any further questions feel free to ask.

Jul 18, 2014 | Cars & Trucks

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alternator problem

Easy way to check with a voltmeter. Check battery voltage on the battery terminals with key off, engine off, and then check voltage with engine running.
Engine off, a good battery should have voltage between 12.6 volts and 12.9 volts. With engine running, battery voltage should be a minimum of 13.5 volts, somewhere between 13.5 and 14.5 volts. This would indicate the alternator is good and is charging the battery. If voltage is less than 13.5 volts, if it only shows same volts as when not running, the alternator is not working right. Take it off and have tested for free at a parts store. It could be a bad alternator or it could be that the wiring between alternator and battery has a problem. If alternator tests good, start looking into the connections between alternator and battery.
Does your battery or alternator light stay on when engine is running? This would indicate a charging system problem. Time for the voltmeter test.

Apr 10, 2014 | 2000 Toyota Avalon

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battery voltage is 14-18 V when engine is running

alternator test to see if the alternator is overcharging or wire harness problem do an easy test find the connector on the alt and while running with multimeter at battery check the voltage when unplugged and plugged sometimes by unpluging the alternator it releases the voltage meter build in the alt

Apr 06, 2014 | 2002 Kia Optima

1 Answer

Batterie light stays on after changing alternator

The yellow wire in your Alternator plug Have a "Fuse Link" at the starter relay. If that fuse link is bad the alternator will not charge. To test jump the yellow wire with the hot wire at the alternator and if the alternator is new it should charge. Check and install the fuse links.

Other details that you can try:
First ensure your battery terminals are clean and free of corrosion. Make sure you use a battery tool to clean them up to ensure a good connection. reconnect and tighten.

NOTE: Some electrical systems need to have the system computer reset after changing an alternator. If you changed the battery first, then changed the alternator, this may not have happened. Sometimes it's as easy as fully disconnecting both terminals and reconnecting the battery.
Check the voltage from the positive terminal of the battery to the negative terminal on the battery(record this).

Then check voltage from the positive terminal of the battery to where the negative terminal connects to the block. if this reading is lower your negative battery cable may be the problem. I've had them crystallize before from age so badly that they lost flexibility and began breaking internally. Replace it.

Then check voltage from the smaller positive cable post on the alternator and the negative terminal on the battery. If this is lower the smaller cable may be the problem. Replace it.

Then check voltage from where your positive cable hooks up to the solenoid and to the negative terminal on the battery. if this is lower your positive battery cable may be the problem. Replace it.

Charge the battery fully and take the vehicle to a local auto parts store and see if they can run a charging system test (usually a free service). They should be able to tell you what kind of shape your battery is in and the alternator output. A good alternator will put out 14+ volts, if it's putting out 12-14 volts it's wearing out and needs replaced.

If your alternator is putting out 10-10.5 volts or less means one of the diode pairs are bad, 5-5.25 volts or less 2 diode pairs are bad. Either way the alternator is not charging the battery and it's the fault of the voltage regulator.

Ask the person doing the test if he can tell you what the field voltage is on the alternator. If they can and it is around 12 volts or more you can probably bypass the next test.

Start the vehicle and hold a steel tool near the back of the alternator (not on the pulley side). It should be drawn magnetically to the center of the alternator. If it doesn't your alternator is not generating the magnetic field needed, to generate electricity. This could be due to a bad alternator or wiring.

WARNING: The next test is the "old fashioned" way we shade-tree mechanics used to do this. It can be done with the engine running in most cases, but you must be extremely careful that you don't get clothing or long hair anywhere near the pulleys. You do this at your own risk. If you are uncomfortable with taking such a risk, have your mechanic look into it. Disconnect the two wire box-like electrical connector from the alternator's voltage regulator and see if there is any voltage (should be around 12 or more volts DC) from the wires going to the alternator. You can try testing this with the engine shut down and the key on, but it may not work on all vehicles.

With connector disconnected, if the voltage is less than 12volts or non-existent, it's a wiring problem. - With connector disconnected, if it is 12 volts or above it's probably the alternator (Bad windings.)
Set the multimeter to Ohms. Touch probes together and calibrate the needle to zero on right side of meter readout. (If the needle does not move to the right, you may need to replace the meter's battery or fuse). With the Alternator connector disconnected check the resistance of the alternator at the connector blades. If the needle goes to infinity, there is an open circuit in the windings. Replace the alternator.

Other things that can cause charging system problems:

  • Excessive starter draw - Remove starter and take to parts store for testing
  • Bad solenoid
  • Failed engine compartment fuses or resisters - Look for and check big rectangular ceramic ones as well on antique/classic vehicles
  • Failed fusible links
  • Failing ignition switch - Usually under the dash, Not at the key
  • Wiring to the key assembly inside the steering column - or on the dash older vehicles
  • Bad computer modules
  • Electrical wiring - This one takes the longest to isolate
  • Particularly hot wires arcing to ground
  • Some other Windstar threads suggest checking wiring bundles under the rubber boots at door hinges.
  • Other unassociated electrical components shorting to ground and placing a drain on the system - could be anything from a cigarette lighter, to lighting, to electric radiator fans failing to shut off, ignition coil, radio, sensor probes shorting to ground, etc. etc
Hope this help (remember rated and comment this).

Mar 19, 2010 | 2000 Ford Windstar

1 Answer

1989 volvo 740 keeps dieing

I sound like your battery is not charging on its own, the battery is charged by the alternator, the easy way to test the alternator is by using a volt meter ( cheap volt meters a found at autoparts stores on most hardware stores starting around 20 bucks) Test the voltage ant the battery with the car off, then start the car, (jump start if nesasary) then test the voltage again. with the car off the voltage should be around 11.5-12.8 alittle more is ok, but not to much lower, with the car running the voltage should change to around 13-14 volts. if the voltage does not change or drops then the battery is NOT being charged. if its not getting charge then check for loss or corroded wires or wire end terminals,sometimes the is an altenator fuse ( usually uder the hood ether the fuse and relay box or at the battery terminal ) if all is ok the alternator needs to be tested at some place, most places like napa, or westernauto will do it for free, it will need to be removed from the car to do this, since at this point it is most likely dead, you will be taking out to replace anyway.
"Good luck, And I hope for it to be a cheap and easy fix"

Feb 06, 2009 | 1989 Volvo 740

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