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Alternators
An alternator is an old term for electric generator that converts mechanical energy to electrical energy producing alternating current. Alternators are mainly used for recharging batteries and to power electrical loads of vehicles.
4,629 Questions
How do you test alternator charge with a digital multimeter?
Check the gauges, if the car is equipped with them. If you have a volt/amp gauge, it will read the alternator output for you. Turn on the blower fan for the AC or Heater, the headlamps, and any other accessories that put a strain on the alternator, and watch the gauge to see if it decreases voltage or amperage. As a rule, if the voltmeter is higher when the engine is running then when the engine is not, you can confidently assume that the alternator is charging. Check it at the battery with the engine running. It will show at least 13.5 volts if the alternator is good. If these values decrease when you turn on electrical accessories, the alternator may be weak. Listen to the alternator while the engine is running. If there is a problem with the bearings you may hear a squealing sound coming from the front of the car, which becomes louder with more electrical accessories using power at the same time. Feel the alternator after the engine has run a few minutes and you turn the engine off. If it is very hot, you may have wear to the bearings or the insulation on the copper windings may be breaking down, an indication the part may fail soon.
To actually measure the charging current on a cheap modern digital volt meter: Set meter to most accurate voltage range, with the engine off measure the voltage between chassis and chassis connection at the battery, this should be nearly 0 volts, now turn the headlights on, the headflights will draw about 10 Amps and the volts drop across battery earth to chassis will show about 50 millivolts dependent on the resistance of the earth strap. Remember 50mV is proportional to 10 Amps. Turn the headlights off and start the engine, the meter will show the charging current and this will be in the opposite polarity as the current will flow in the opposite (charging) direction. for example if the meter shows 100mV the alternator will be charging at 20A. turn the headlights on and you will see the charging current to the battery reduce as half the alternator current goes into the lights.
There should be no power to the steering arms, you have a hot wire going to ground somewhere there, pull various system fuses and retest with the light to narrow the search down to a specific electrical system, then at least you will know where to look.
Why would the battery light come on and off while shifting through gears?
I'm not familiar with your vehicle, but have to assume that "shifting through gears" means you have a manual transmission. If that is the case, then I suspect that the "battery light" coming on occurs WHILE the engine has dropped back to IDLE. The charge indicator light is designed to alert the driver that more electricity is being drawn from the battery than the charging system is able to put into the battery. The electrical output of the alternator is proportional [at lower rpm] to the speed that the alternator is turning. The condition you describe suggests a couple of possible causes: 1. That the IDLE SPEED of your engine is set TOO LOW [USUALLY, and PROBABLY, the most likely cause] or 2. For some reason the output from the alternator is weak [very unlikely]. I suggest that you have your vehicle's charging system checked out by a QUALIFIED mechanic or autmotive electrical technician. The correction may require no more than an ADJUSTMENT of the IDLE SPEED. j3h. Becuse the RPMs of the engine go down and the alternater is not producing as much as the engin is using. Replace the alternater befoe it kills you battery...
Where is the alternator and battery ground in a 1981 Nissan 280zx?
Negative battery cable - a solid metal part of the engine
A couple of things come to mind on this problem. First, just because you purchased a new alternator does not guarantee that it will work properly. I have purchased several in my lifetime that I've had to take back to the parts house and have them checked...only to have them give me another because their "new or rebuilt" alternator was faulty. Most auto parts stores have the capability of checking the alternator (always a good idea to have them do before walking out the door with the "new" alternator...will save you a trip and much frustration).
Secondly, your battery may have a partially shorted cell. Your car battery is actually comprised of 6 cells, each producing approximately 2 volts. When a battery ages, some of the material on the lead plates will sluff off of the plates and settle in the bottom of the battery. If this material builds up to the point where it touches the cell plates, it will short out those plates. Sometimes it's just enough to prevent the battery from coming to a full charge (but not enough to give indications of a bad battery when checking unloaded voltage.) Take your battery to an auto parts place and they will check it for free for this condition. The cause for your check engine light can be determined with an ODB-II scanner. This scanner plugs into a special plug underneath your stearing column. It then collects error information from your Astro's computer. It will also allow you to clear your Check Engine light. Many auto parts stores have tool rental/loaner programs. The one I use simply has you pay the full amount for the scanner and then you can bring it back at anytime for a full refund. By the way, ODB-II scanners are generic to all vehicles sold in the US (after 1997...not absolutely sure on the date). Anyway, if you rent the tool, it would be a good time to check all of your vehicles...often they will have error codes that will give indication of a pending problem..could save you a hassle by taking care of the problem before a component completely fails).
The RPM change affecting the light seems to indicate that it's the alternator. Perhaps it has a bad voltage regulator? Maybe it's not the right alternator for your car?
What kind of metal is in an alternator?
The case--aluminum
The rotor--steel
The windings (field and armature)--copper
The shaft--steel
The bearings (bushings)--phosphor bronze
The fasteners (bolts, screws, nuts)--steel
The pulley--steel
How do you install a alternator on a Infiniti J30?
How to Change an Alternator: Video Series check related link below
How do you know if you have a bad battery or an alternator?
Your local autoparts store can test the electrical system of your vehicle to determine what is at fault.
How can you tell when your alternator is going bad?
Normally your battery warning light comes on to warn you that it is not getting sufficient charge. If that does not come on then its either a faulty battery or the light does not work as well.
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It is possible that a bad diode in the alternator will prevent it from delivering full rated current, while still keeping the light off. The general way to tell is to be sensitive to the way the engine cranks. If it is cranking slow, then you have a starter and/or alternator and/or battery problem. Unfortunately, one can cause the other to fail, so you definitely need a good mechanic to check out everything when something is replaced.
As an example of a worst case scenario, the bad diode prevents the battery from being fully recharged after starting the engine. The battery voltage falls. This causes the starter to pull more current on subsequent starts. It begins to overheat. Maybe a winding shorts out and the Q factor goes to pot. One day, the starter pulls so much current that it buckles the plates in the battery. Now you have a bad alternator, a bad starter, and a bad battery. Replacing one, without carefully checking the other two, could well cause the new component to fail again.
How much should it cost to replace an alternator in a '97 Nissan Sentra?
I have just got it done. it costs 270 $. I just had an alternator replced in a 1996 Sentra. It cost $295.00 on 3/2/2006. The Firestone dealer wanted $325.00, plus tax, but I told him my son said it was too much. (My son is a mechanic living in another state.) My advice: Never accept the first price a mechanic gives you! Palavering
Why won't a 1995 Saturn SL2 twin cam start even after replacing the battery?
If it doesn't crank, then it will be the starter, or ignition switch. It might have a bad starter
you also might have a bad alternator one of these 3 would be my first guess Also be sure to check the starter fuse located in the fuse box under the hood, probley near the battery, there will be a digram under the cover of the fuse box. If you pull the fuse and its black or brown in the middle then it burnt out. this s your cheapest fix. If it happens again, take it to a shop and have them look for a wire short. Sincerly, Matthew Self Slip Stream Customs
How do you know if 2004 dodge ram 1500 alternator is bad?
with vehicle running pull posative side battery terminal off if it quits alternator is bad
Is it possible to bypass the box on the back of the alternator?
i presume you are talking about the rectifier regulator
and the answer is no it would not charge a battery without this if you don't know what the part is i dought you will be able to know what is wrong with your alternator you could have winding problems or brush problems also
Why does ny 1996 contour alternator not charge-- bench tested ok 2 times?
check your fuses and proper ground
Ironically your question answers your question.If the battery light came on,and the battery is old,has poor connection,or maybe has a dead cell in the battery it would cause this problem.I would remove the battery if the vehicle will not run,take it to auto zone,or advance auto and have them do a battery test on it.I would guess your battery is either at the end of it's life in term of 48 month,72 month as examples or it may have a dead cell which will cause the vehicle to HAVE NO POWER to the alternator and can be compared to a vehicle with no battery literally.Take the battery out,get it checked I bet money you need a new battery even if the battery is not that old it can happen at any time and I speak from experience.Had a 2 year old battery die at a fuel stop got in turn the key nothing not even horn,lights,door buzzer,radio etc.Dead cell in battery.
Are you getting any messages in your message center? Stuff like "check Charging System"?
What voltage is the battery sitting at with the motor running and the lights on?
did you consider the alternator might be bad? Yes, I know, new alternator, but that doesn't mean it's always 100% good.
Why we are insulating windings of a motor alternator?
If the windings weren't insulated then there would be no reason for the current to go all the way through the wires. It would just go staright across from one terminal to the other.
What is a brush and how many of them are there in an alternator of a motor vehicle?
What is a brush and how many of them are there in a alternator of a motor vehicle?
How do you replace the alternator on a 1992 Buick Park Avenue?
Hey Joe==Take the serpentine belt off and then take the neg battery cable off then remove the wires from the alternator then take the bolts out and remove the alternator. GoodluckJoe
How do you replace the alternator on a 1992 Chevy Lumina 3.4L Z34 V6?
undo ground wire cable then jack the car up. Much easier from the bottom. Remove the belt by loosening the adjuster until belt can be rolled off pulley.There are 2 12 mm bolts at the top of the alternator .one can be seen from the front without much trouble the other you must feel for from the back . To get the unit to clear power steering and A/c lines it is best to let down the sway bar. undo battery wire from back of alternator. I think it will take longer than 20 minutes for the turbo model .
How do you replace the alternator on a 1993 Jeep Cherokee Sport?
start by loosening the bolts holding the alternator to the bracket.
Remove the wiring connections before extracting the unit, to avoid damaging the harness. There are 4 terminals, and one wiring support bolt; The Ground, wiring support, and main output (inside the plastic "cup" are 10mm, and the small Field terminals are 7mm.
should be about a 30 minute job.
It's worth mentioning that the lower bolt, as well as the wiring terminal posts, are much more easily reached from beneath the vehicle, with the 'splash shield" folded back.
Additionally, at least one source recommends removing the front alternator mounting plate from beneath the vehicle to make extraction of the old unit easier; the stock 90 amp DENSO unit BARELY squeezes past the AC Evaporator lines for removal from the top.
while you are at it you may as well go with a higher amp alternator. maybe a 120 or 136 amp alternator since cost wise its close. that way you'll have more power and always a reliable charge system. a n\high amp alternator from a 98 grand Cherokee or durango v8 should fit perfectly. if nothing else you may have to just grind a hair of metal off the bracket, even a file will work for this. take the bracket off if need be otherwise it should just bolt right on.
after that you will be able to run all types of lights, heater, a/c, accessories and your headlights wont ever get dimmer.
enjoy!
I recommend putting a block udder the oil pan and jacking up the engine a little bit and the alternator will come out easier it is a tight squeeze and without doing that I would have never got it out
