Top 5 Causes of an Alternator Not Charging

The main functions of an alternator are to generate electricity for the electrical components of the vehicle and to charge its battery. The alternator produces this electrical energy by converting mechanical energy. If you were to try and start your vehicle without an alternator, the battery alone would not be able to produce enough power to get the engine running.

Even if you had a new car battery and were lucky enough to turn the engine over, it would probably run for about 10 minutes before the power cuts out. The alternator is necessary to keep the battery recharged and to alternate the electrical current throughout the many components of your vehicle to keep them powered.

Causes of Alternator Not Charging the Battery

A lot of people get confused when they begin to have electrical problems with their vehicle. It’s easy to misdiagnose these problems as being a bad battery instead of a bad alternator. To understand the difference, you must first learn about what causes an alternator to stop charging. Then, you can inspect the vehicle and determine if the problem is your alternator.

Below are the top 5 causes of an alternator not charging:

#1 – Computer Error

ECU error

Most people are driving cars made within the last 20 years. These newer cars all have a central computer system or engine control unit (ECU) which manages and operates the vehicle’s components and parts.

This computer manages the alternator as well. Therefore, all it would take is a computer error and the result would be a malfunctioning alternator, preventing it from charging.

#2 – Broken Belt or Pulley

broken belt

The belt and pulley produce the mechanical power which gets converted into electrical energy by the alternator. Your belt can easily break if it gets stretched out too much, causing it to snap apart.

The pulley can also get damaged after a while. In either case, the alternator will no longer be able to produce a charge for the battery.

#3 – Blown Fuse

bad fuse

There are certain models of car which have alternators dependent on a particular fuse to operate. However, these fuses can blow due to a power surge or simply from old age. Once that happens, the alternator will no longer charge the battery.

Not all vehicles have these fuses, so you will have to check your owner’s manual to see if your car has them. If so, this is well worth investigating in the event your car battery is not charging properly.

#4 – Wiring Issues

alternator wiring

There are numerous wiring components in a vehicle that help produce power for the alternator. All it would take is for one wire to be disconnected or cut for power to stop being generated. As a result, the alternator won’t be able to charge the battery until the wire is repaired or replaced.

#5 – Bad Alternator or Battery

bad car battery

Alternators and batteries do not last forever, and each have their own lifespans. A car battery will last from 2 to 5 years, depending on how often you drive and the climate where you live. Batteries generally last longer in colder environments and shorter in hotter environments. Alternators will last about 7 years or every 80,000 miles.

How to Fix

The most common reason for an alternator failing to charge a battery is one of them going bad. You can easily test the voltage by connecting a voltmeter to your battery while the engine is off. The voltage reading should be between 12 and 13 volts. You can automatically assume there’s a battery problem when the reading is lower.

In the event your battery’s good, start the vehicle and get the engine up to 2,000 RPM. This will put a lot more demand on the alternator.  A decreasing voltage reading on your voltmeter indicates you have an alternator problem.

 

Comments

    • Check under the cover of your fuse box or in the car manual to see where the alternator fuse is and simply replace it with the same fuse type.

      • All my fuses are good and have new battery in my 1990 corolla but lights,hazards and hooter aren’t working while car is running. Battery isn’t charging. When I disconnect the battery while the car is on…it does immediately. How can I fix this?

    • I have a 2008 Jeep Liberty. Ive replaced the alternator and battery. Both brand new and the alternator isnt charging the battery. The belt and pulleys are all turning the tensioner is good and belt is on tight. Where else can i look. Theres no fuse for the alternator. Alternator has no power sent to the battery and everything is hooked up correctly. This is my third alternator because i thought i kept buying bad ones. Could it be a bad ground somewhere or the pcm bad? Really need help.

      • Your story is my story with my 2006 Liberty. Third alternator reads only 11.8 volts charge. I guess it’s time to look at all of the wiring coming from and going to the alternator.

      • I have a 97 Oldsmobile Aurora New battery new alternator but car won’t start I noticed that one of the screw’s (bolts) to mount the alternator is not fully connected can this be the problem??

      • Can a damaged cable leading from positive terminal to fuse box cause the alternator not to charge? Swapped out battery and alternator and van ran fine for 4 days then just shut off.

    • Since you have a GM, the first thing I can think of is to check to make sure the battery/ALT/CHARGE warning light bulb in the dash is not out. It doesn’t make much sense but that’s how they’re wired. If the battery “idiot” light in the instrument cluster doesn’t light momentarily when the ignition is turned ON, the bulb is bad and the charging system will not work.

      If the bulb IS working, make sure you check the voltage at the battery and at the alternator. The numbers should be similar.

    • Good morning. I have a 2003 Toyota Corolla. I experience some battery or alternator problems which make me to kick-start the car. My car doesn’t have the 100a fuse inserted and where it’s supposed to be the metal clips are bent to touch each other. Can I just open it and insert a new fuse or are there possibly other reasons why it has been bypassed?

  1. I have VW Touareg V6 2008. Car is running but battery doesn’t charge immediately when the car is started. If I continue running the car for 15 to 30 minutes and switched off the car then start again, the battery will charge. I am confuse to locate what is the exact error or problem.

    Please need some advise.
    thank you

  2. I have an 05 tahoe replaced alternator xmas eve now my chargein system failure display showed batteries fine alternators fine the cord that plugs into the alterbator is not giving power any suggestions

    • Looks like you narrowed it down to a wiring issue. There may be a damaged wire, wiring harness, or short somewhere. I’d look at replacing the wiring harness.

  3. I would like to know when you connect a alternator, if your power wires is short can you use a smaller size wire to connect it to the actual wire that runs to the engin and battery?

  4. I accidentally swapped the battery terminals but corrected them and the car started, it showed the battery signal which suggest alternator is not charging the battery, i found that there are two fuses died, i replaced them and ON the ignition, the fuses died again. What could be the reason in this case?

        • The voltage regulator is responsible for making sure the correct voltage is being sent to recharge the car’s battery. In the original commenter’s question, it’s possible reversing the battery terminals caused permanent damage to the regulator (it fried it) and it no longer allows the battery to be charged.

  5. I have a Ford Mondeo 2 l diesel 2011 the battery warning light comes on had battery tested it’s good alternator is putting in 13.9 volts what could the problem be?

  6. I tried to install a car stereo and by pass the factory amplifier and computer but now my battery won’t hold it’s charge it charges and starts the car up but won’t hold the charge the battery indicator the brake indicator and the security light is on on the dash this is on a Cadillac Seville sls 2001 do you have an idea

  7. I just got a new alternator and battery an now when I turn the key it’s just making the clicking sound and everything in come on the my Nissan Murano but it isn’t starting

    • Even though you replaced the battery, make sure there’s no corrosion on the battery cables which connect to it and that they are connected tightly to the posts on the battery. If that’s fine, you may have an issue (or loose connection) with the starter.

    • I have a 2007 Mitsubishi Raider 3.7 L battery light is on battery is good alternator is good cannot find a fuse that is bad any suggestions I switched battery and alternator from another vehicle and still have same results before a short time ago when I took the cable off the battery the car was running now the car dies email me [removed] please.

  8. Hi so I have a Mitsubishi 2009 Galant and I’ve had my alternator replace led twice over the last couple months but recently again my battery has stopped holding charge, is there anything that really might be buggin instead of the alternator itself ?

    • You didn’t mention how old the battery is but I assume you’ve had it tested before replacing the alternator. Other things to look at: check all cables attached to alternator and battery (make sure they’re tight with no corrosion), check for blown fuses, and check belt condition and tension.

  9. I have a 2003 Ford expedition my battery light came on after I replaced the fuse box I thought it was the alternator I put a new one in then thought it was the battery put a new one in and the battery light is still on how do I fix it

    • Make sure all your cables have a good connection with no corrosion and your belt is in good condition with proper tension. Not sure if the Expedition has one, but some vehicles have a remote voltage regulator (instead of being part of the alternator) which may cause problems. All related fuses look good?

      • I have a 2011 Honda CRV. Initially the AC stopped blowing cold air, followed by battery light coming on, after a longer drive all the lights started coming in: abs, awd, hand brake… Barely made it to partssource they changed the battery it was two years old) , it still didn’t charge… Soni went to a mechanic, changed the alternator, still didn’t work… Replaced the ac compressor Clutch switch, no change..
        Not sure what to do anymore, worried Honda will rip me off

  10. My alternator was repaired , they changed the regulator amd the other part, it is for Mercedes Benz V230 , it only charged for 3 to 4 days and now its undercharging again and I have a new battery , what. Could be the problem

  11. Hi I have A170 Benz it show altenator problem and the steer wheel does not move it’s 2005 model please help me out

    • If you alternator (or battery) fails, it will not allow the power steering pump to work. This means your steering wheel will be extremely hard (or impossible) to turn without power assistance.

  12. I have a toyota hiace truck. Its not charging the battery but the day i was cleaning the engine after putting engine cleaner and somw water that spilled on to the alternator. It started charging. But this didnt last for long. What might be the problem.

  13. 2003 dodge dakota has new alternator and battery it starts easy but after a few minutes gauge shows no charge and check gauges light comes on
    Turn off ignition and wait about 5 minutes and start it will show 12 -13 on gauge in dash what might be wrong

  14. My car is Toyota Corolla Quest 2015 on the clock it is 245000km and it’s not charging will that means a car of that old the alternator is already damaged?

  15. Hi I have a 2003 Lincoln Navigator I bought a new battery a month ago since I took it to autozone to get it tested and they said the battery wasn’t working that in 3 months it was going to go bad so I bought a new one and had someone put it but since I didn’t use the car for 3 weeks after they put the new battery it wouldn’t start so I have to jumpstart it every time and I go into autozone and they check everything and told me that the problem is the alternator but I just bought it a year ago also . Is the alternator the problem? Or what else could it be ?

    • Sounds like a poor connection somewhere especially since you can jump start the car. Check to make sure the cables are attached to the battery posts tightly and make sure there is no corrosion on the ends of the cables. A bad alternator won’t prevent you from starting your car if the battery is charged.

  16. I have had 3 alternators and 2 batteries replaced in 6 months, the check engine light came on yesterday after I jumped the battery, they checked the system and no errors came up; suggested something in the computer

    • If your check engine light is on but no code is picked up by the scanner, I can almost guarantee you the wrong scan tool is being used or it’s one of those cheap $15 code readers. Either go to a different mechanic or take it to Autozone. They as well as some other auto parts stores will perform a diagnostic scan for free.

  17. I HAVE A SUBARU IMPREZA GG2 whenever i i start the car it sounds as if it has no power, like has a miss the the idling becomes normal while driving i turn on the lights the this is all the lights plus fog the car looses power and im forced to turn off the fog , if put on full lights the car stalls and looses power. the alternator i had it checked and the guy told me it was charging , help a brother

  18. I can honestly say from recent experience, The best scenario to check the fuse, is when you have a brand new alternator and a brand new battery(or good battery). And you find yourself getting jump-offs, and the car stalling after so many minutes or seconds. That was happening to me after I brought a used car 2 weeks ago. I checked the fuse box and the battery fuse in particular was the wrong fuse. So not only can it be a blown fuse, it can be the wrong one. I got the right fuse in my car is running A1.
    So yes if you know your alternator is good and your battery is good, and your battery is continuously drained, it is definitely worth investigating. I’m a living Witness.

  19. I have a 2017 hyundai santa fe..was driving down the road and every warning light possible started flashing and car died ..battery was dead and alternator not charging..had alt and battery both tested and both were bad .put new alt on new battery still no charge coming from alt.except sometimes thr battery light will go off and will charge but as soon as the car is turned off and you restart it the battery light and discharge warning come back on and drains battery ..im lost cant seem to find an alt fuse cause no info is available to me online or manuels to be bought..

  20. 2010 Kia Forte Ex

    The battery light came on one day and slowly the instruments are cutting out. E.g, the rear defroster and heated mirrors don’t work, running daylight don’t work, and the AC doesn’t work.

    I took the car into a mechanic shop thinking that my alternator is bad, but the location of the alternator in the car is tough to get to (located underneath the power steering pump). The alternator and battery were replaced a few months ago in late February and there were no problem with anything until 2 weeks ago.

    I took the car to a mechanic shop nearby but they were unable to reach the alternators location to do proper testing. Could it be a fuse or wiring because the alternator doesn’t make any wining or grinding noises at 2000 rpms. And the belt doesn’t look like there is any tears or wearing. I believe that was replaced as well.

    Any suggestions??

  21. I have a 2008 Ford Focus 1.6 tdci. The battery voltage (battery only 12 months old) is 12.6 volts, when I start the engine it goes up to 13 then to 14 but after 30 seconds or so the battery light on the dash comes on and the voltage drops to 13.6 and fluctuated between 13.6 and 13.7. What is going on?

  22. I have a 2006 Hyundai Tuscan and I have put in two new alternators and battery but they keep blowing. Even the little fuse on the battery. There is no wires that are damaged but I don’t know what else to try. Any clues on what it could be?

    • Electrical problems are always the worst to diagnose. I’d recommend taking it to an auto electrical repair shop for advanced diagnostics. Some people may enjoy trying to troubleshoot but to me, it’s not worth the headache most of the time.

  23. I have a 2003 Ford Taurus and it’s not charging at all
    I have a brand new Alternator , Brand new Battery and a Brand new Starter.
    My Alternator Light came on and I went to the auto part store where I had bought the alternator and it was tested on the car and wasn’t charging so we thought the voltage regulator had gone bad within 24 hours so I took it off right there i the parking lot and they took it in and did a bench test on the Alternator and it passed the bench test 4 times in a row. Put it back on and it wasn’t charging again. What else could be the problem ??
    I have had 6 different people say that there is a ground off , Broken off or just Missing all together. I’m lost so could someone please help me out or point me in the right direction. PLEASE !
    I’ve been without my car for 3 weeks now

    • Im having the exact same issue. Im on my 5th alternator because its not charging on the car but passes on a bench test everytime. If you find a solution please let me know too. Been 2 months now borrowing a buddys truck.

  24. I have a 2005 Honda civic dx. Replaced the alternator but the battery tries to start but never turns over. When you try to jump it still wont start. Is it possible that when the alternator went out it screwed the battery up and now wont charge enough to start

  25. Testing a battery with a voltage meter is fine, but each cell needs to be tested separately with a hydrometer, (old school). There are six cells in a 12 volt battery. One cell could be floating three balls. Another two and another one none. No ball floating indicated a dead cell. This battery could check OK on a voltage meter, but it would not hold a charge for an extended time. ALL cars, new or old, has a slight parasitic draw to keep memory of components alive and will drain an already weak battery over time. A car runs off the battery. The alternator is there to keep the battery charged. That is its sole purpose. An alternator goes dead and the car will run on the battery alone until the battery goes dead, then the car quits running.

  26. Am a technician and one Hyundai Santa Fe is having alternator problem I changed it and it’s not working I have checked the fuses and all the same what can I do?

  27. I have Toyota Yaris 1.5 2010 the alternator is not charging the battery or slow charging and all the fuse are replaced but still acting up , what can i do to sort the issue or diagnose the fault on the alternator .

  28. I have a 2006 jeep liberty and the engine light goes on just put a new alternator and battery and it start to lower the battery little what could it be

  29. I have a Honda crossroad 2007 model. One time it stopped charging and the mechanic didn’t find fault with fuses and Alternator. The only fault found was one of the cables was not supplying power to the Alternator, then he had to cut the Black and White wire and connect to another black and white wire connected to the plugs and the alternator started working. Now the check engine, VSA and another warning light are on the dash board always. After taking it for scan, The following codes appeared P0141, P1298, P0102 and 83-1 ECM/PCM relation failure. What could be the problem?

  30. 2007 Toyota Camry se 2.4 engine. I replace battery and alternator in March 2019. also replace alternator in June 2019 both rebuilt alternators. replace alternator in Sept 2019 with new not rebuilt alternator. The first 30 days or so the car start right. Now the car start slow like before. Have any ideas?

    • Run a voltage test on your battery and alternator. There might be a drain somewhere. Also, could be your starter going out.

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