Questions tagged [alternator]

An engine accessory which generates alternating current (AC). The electricity is then fed through diodes which converts it from AC to direct current (DC), which is usable by the automobile in general. The alternator is usually driven by belts which are connected to the crankshaft of the engine which provides the motion to produce power.

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Why do cars die after removing jumper cables?

I work at an auction site where we have to move cars from one spot to another. Often, we get a car with a dead battery that we have to jump. I've noticed that if the jumper cables are removed a ...
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Will fitting a physically bigger battery reduce the working life of the alternator?

I have fitted a much larger 12v battery to a car. I modified the clamp and battery tray to make it fit securely, it's almost twice the size of the original and has a much higher CCA rating. It works ...
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21 votes
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Can a weak battery destroy an alternator?

I've heard a story that a weak vehicle battery can destroy an alternator or cause an alternator to fail early. Is this true, or is it largely fiction?
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17 votes
3 answers
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Car battery at 10v, then shows 14,5v while car running after boost, then when car turns off, drops to 10v again within a minute

Yesterday car suddenly didn't start. We boosted it and drove for an hour. When parked, it would restart immediately. But after waiting 1 minute, it wouldn't start again. Today I measured the battery: ...
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2 answers
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How to determine exactly what's wrong with my alternator?

My 98 Mazda 626 GF 2L uses an 80 amp fp34 A2TB0191 alternator with an internal voltage regulator. I did a little test where it I turned on the bright lights, AC, radio, rear defogger and opened the ...
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13 votes
5 answers
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Car won't start after sitting for 2 years even with a jump. Is it a starter or alternator issue?

My parents have a 2001 Pontiac Aztek that's been sitting for two years. Apparently, before they stopped using it, there was an oil leak that caused starter problems (they couldn't find the leak), and ...
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13 votes
2 answers
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Non-functional gas pedal, engine stalling, dead battery: broken alternator?

I have a 2005 Nissan Sentra. The following happened twice within a few days: I stopped at a red light. When the light turned green, pressing the gas pedal had no effect at all. However, the car would ...
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4 answers
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How to assess battery charge level and alternator performance?

What diagnostics can be done to to assess battery charge level? I'm interested both in one-off tests like can be done in car service and also continuous monitoring during normal use. Car panels ...
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12 votes
7 answers
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Can a car AC unit be run on just the car battery?

This might be a silly question but I was wondering if a car AC unit be run off entirely on battery or alternator? As this could help in Preventing power loss during important times such as ...
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12 votes
7 answers
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Why can't alternators provide full current at idle?

I was reading about load testing and full fielding alternators in a few different books I've got, and one of the points they all made was that to test an alternator's maximum output (or close to it) ...
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Can I safely upgrade to an AGM battery?

AGM batteries are capable of being charged at a faster rate, and may draw additional amperage from the alternator if it is not regulated. Many cars that come with AGM batteries have special charge ...
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Is any power from the alternator 'free'?

Cars generally (and specifically a Honda Accord 2002) are not very energy-efficient. Given all the inefficiencies, is it "free" to plug in, say, a smartphone into a car to charge while I am driving? ...
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how fast does the alternator charge the battery?

It would appear that the common word of wisdom is that car alternators provide 50A of output. I actually looked at the supposed specs for my 2008 Jetta 2.5L on the internet -- a compact car -- and it ...
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3 answers
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How can I clean the dirt build-up in my alternator?

The alternator in my '04 Lumina SS is its Achilles' heel. It lasts a few years before it starts to overcharge the battery, after which the only practical remedy is to replace it. While I cannot be ...
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6 answers
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Noise in stereo that changes pitch with engine RPM

This is a question of curiosity. I have a '98 Acura Integra, a cheap car stereo with a 3.5mm aux in, a cheap inverter and a smart phone. If I have the smart phone audio hooked up to the car stereo and ...
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1 answer
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Car battery dead for a while... now it won't charge?

So, my car battery died 4 months ago while it was unused in my garage during the summer (interior dome light left on for months). I went to jump start it this morning, ran it 20km ( 30 minutes ) to ...
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9 votes
1 answer
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Why would turning on the A/C affect my alternator output voltage?

So yet another chapter unfolds in the A/C gremlin saga of my LS1 Chevy. Backdrop A/C compressor is relatively new (2 years old) One of the belts is squeaking (not sure which one) Recently performed a ...
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2 Volts on Car Battery

My car battery has gone completely flat after leaving my car parked up for about a month. Tried turning over the car today, and none of the lights on the dash light up. Ran a multimeter across the ...
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8 votes
4 answers
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How to diagnose a starter motor that does not work

My e46 M3 would not start when I got to the parking garage after work. When I first turned the key, I heard a sound like grinding gears, but I was so startled that I immediately stopped trying to ...
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Will an auxiliary battery hurt a vehicle's alternator?

I am going to be road tripping and living out of my SUV for a while. I need a way to power a tiny portable cooler/fridge 24/7 and would like to be able to power my cell phone, laptop, and maybe a few ...
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3 answers
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Does idle RPM increase when there is heavy load on the electrical system?

I am thinking about installing a 500w halogen (HDX brand) on the roll bar in my jeep as the dome light because often I work in the back when it is dark or when I would like more light. The 500w light ...
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8 votes
1 answer
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Connecting to the Battery During Emissions Testing to Measure RPMs?

When doing emissions testing, they connect to the battery, either directly, or using the cigarette lighter socket. I'm assuming that this is to measure the RPMs, as the only other thing connected ...
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8 votes
2 answers
196 views

Semi-permanent power inverter

I'd like to install a semi-permanent 500 watt inverter connected to the car battery for greater power delivery. The battery is in the passenger area, so there's no need to run wiring through the ...
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3 answers
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Kawasaki EX650 - What causes a stator to burn out?

My motorcycle recently required a new stator (plus a new regulator rectifier and battery) because the stator burnt out and fried everything. What are the typical causes of a burnt-out stator? Does ...
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8 votes
1 answer
4k views

Battery light on after new alternator

Car: 2003 Honda Civic Si G1Wh dash cam, 400w amp, 4300k HIDs My alternator failed badly (stereo cutting off), no battery light. Replaced it with a reman Duralast, battery light is on. It shows 14.5v ...
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8 votes
3 answers
1k views

Alternator draining battery

My alternator has been draining my battery in my Datsun 240z since I swapped the engine (VQ35). It takes around 4 days to drain the battery to the point I can't start it. It charges it fine when the ...
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4 answers
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Is it possible to replace the diodes in a rectifier?

I've got an alternator whose diodes are going bad as evidenced by excessive AC output from the alternator. The problem is that the diode assembly is a discontinued part, which I can't even order at ...
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7 votes
3 answers
2k views

Can starter be used as an alternator?

There's probably a legitimate reason why we have 2 different parts for doing 2 different jobs. However an electric motor can also be used as a generator. If the design allows it, why isn't starter ...
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7 votes
2 answers
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Can an engine stop from a bad battery?

The car is a 2005 Toyota Corolla CE. Its engine is the 1ZZ-FE, a 1.8L straight four that runs on gas, not diesel. The alternator is stock, and tests out just fine on the multimeter in both voltage ...
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7 votes
3 answers
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Should an alternator ever run over 14.5V?

Bought a replacement alternator but I am sending it back as I measured and have seen it running over 16.5V. The manual says the regulator should keep it to a max of about 14.5V. I put a brand new and ...
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7 votes
2 answers
8k views

serpentine belt or alternator or battery? car keeps dying?

So I had a leak in my power steering pump and all the fluid was leaking on/near my serpentine belt and my alternator (Acura tsx 2006). I changed the seals on my ps pump and it stopped leaking. Now I'm ...
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7 votes
2 answers
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Does coil rewinding have a negative impact with the existing system?

I have a question towards the rewinding of a coil. Here is the tech spec of the bike:- Battery : 9 Ah, 12 V Generator : 12V, 100 W Fuse: 12V 10A My bike comes with an electrical spec of DC (...
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7 votes
1 answer
2k views

DIY Alternator Belt Tensioner

I've got a diesel engine in my boat, but the previous owner had somehow snapped the alternator bracket, and fitted it fixed to the boat rather than the engine. Now the alternator doesn't move when the ...
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7 votes
3 answers
912 views

Battery and Alternator Pass Test - 2003 Mustang GT

I have a 2003 Ford Mustang GT, I had the battery tested and it will take a jump and start up so naturally I am thinking the alternator is bad. I take the alternator out and have it tested 3 times and ...
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2 answers
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How to detect a failing car alternator..?

Is there some way we can predict that the car alternator is about to fail in order to avoid a discharged battery situation on the road.. Although it will slow the sound of horn and will dim the ...
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7 votes
2 answers
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Why would my Toyota Corolla die soon after starting it?

I have a 1996 Toyota Corolla DX with about 200k miles on it. It runs good for the most part, but recently had a problem where it would not start. Napa tested my alternator, which failed, so I ...
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7 votes
1 answer
2k views

Alternator, Battery, or Fluke?

While we were out running errands yesterday, our car failed to start after a half hour stop at one of our destinations. The first attempt to start the car resulted in nothing but a rapid clicking ...
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7 votes
2 answers
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Alternator vs Battery

I hadn't used my car in a week. Normally it always starts. Then one day after one week it didn't start. I got a jump from my neighbor and i was able to drive around for more than 20 minutes. I stopped ...
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7 votes
2 answers
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How To Remove The Alternator From A 1998 Toyota Corolla 1.3 4E-FE Engine?

I need to remove the alternator from a 1.3 4E-FE engine in a 1998 Toyota Corolla, but have ran out of ideas to do it. This is the photo of the alternator in situ: To the right of the alternator is ...
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7 votes
1 answer
2k views

Alternator isn't charging battery properly. Replace or swap regulator only?

I have a 2015 Honda Fit EX. On my dashboard, there is a small screen that has been displaying "CHECK CHARGE SYSTEM" and displaying warning lights (TPMS, power steering, and stability control). I ...
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7 votes
4 answers
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Can long term parking affect alternator?

My neighbor just told me that his mechanic informed him that leaving a car parked long term not only effects the battery, but can also deteriorate the alternator. The battery having issues makes ...
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7 votes
2 answers
168 views

Can't Start '08 Civic (Diagnosis)

I bought an '08 Honda Civic LX (110k miles). After a few days of flawless driving, I noticed a couple wires NOT connected that were coming from the hood opener-sensor thing. I plugged them together ...
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7 votes
1 answer
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Discharging alternators

I had to replace the original alternator on my '99 Z28 Camaro in January and have had 3 after market and 1 OE and all continue to discharge with air and radio on. Mechanic says it is fine but I think ...
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7 votes
2 answers
22k views

Failing alternator, idler pulley, or something else?

I have 1997 Chevrolet Lumina sedan. I’m trying to diagnose a sound coming from my engine. It is a “whirring” noise that varies with the engine speed (e.g., if I accelerate, the sound becomes louder ...
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6 votes
3 answers
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Alternator dying so junk car?

The alternator store rounded the bolt on my alternator so I can’t get it off my 2004 g35x. I changed the belts (there are two one for ac and one for alternator) since I did that the car has a voltage ...
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6 votes
5 answers
66k views

What happens if I disconnect the battery while the car is running?

There are some comments on the question Are there any modern diesel engines that require electricity to continue running? suggesting that disconnecting the battery while the car is running can damage ...
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6 votes
6 answers
103k views

Is it safe to charge two batteries off of one alternator?

Right now I have a 3000 Watt invertor wired to a 100ah sealed deep cell battery that I trickle charge at night. My plan is to run #6 wire from the battery in the engine to the spare battery so the ...
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6 votes
4 answers
44k views

Technique to test an alternator - fact or fiction?

A friend explained that the following is a simple way to test an alternator to see if it is working: Turn on the vehicle. While it is running, carefully remove one of the 12V battery leads. See if ...
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6 votes
2 answers
2k views

Trying to use a car alternator for a power source (not for car)

I’m trying to use a car alternator for 12 V bench power source, got it all going and getting 14.5 V with no load but once I apply a load to it the output drops to 8.5 V. Is it a faulty alternator or ...
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6 votes
2 answers
1k views

Best way to recharge battery using alternator?

Let's say I'm unable to start my car. I get a jump from another car, and my car is now running and charging the battery. The advice I get next is "leave it running for 45 minutes so it can ...
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