I have a 1990 Honda Civic and the Alternator "burned up". You could smell it...I did a voltage test and found battey voltage while running. I replaced the alternator and Battery and a week later the battery light comes on and it was not charging again. I took out the Alternator and took it to a local Battery shop to be tested. it tested Fine..I put it back in and started looking elswhere. I discovered at this time the regulator is controled by the ECM and the Electronic load Detector(in the underhood fuse block) I aquirred diagnostic info and proceeded to check for any circuit faults. I ran the test numerous times to make sure and kept getting an answer that the ECM was faulty. I had the Customer take it to the dealer for a second opinion and they said it needed an alternator and the ECM was fine..I took out the alternator again and had it tested this time it was burned up..melted inside like the first one...I get another alternator and retested with the same results also testing the Electronic Load Detector (which tested ok).I also checked and cleaned all grounds, battery cables are good.
i was hoping to find that this is a somewhat accuring problem..I have yet to see a computer be at fault in a bad charging system in my 12 yrs of professional experience..Any thoughts?
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Re: Charging System issue!
I had a simular problem, and I have worked on cars for 37 years.
In my case it was the ecm. I tested and tested, come to find out, at higher rpm's, (when car is being driven), the ecm caused the voltage regulator to stay in a high charge situation, which burnt up the alternator, changed it, and was fine.
I'm not saying it will work in your case, but you tried everything else.
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Due to the nature of the battery technology used with vehicles the alternator is mostly incapable of charging the battery. The car alternator is designed to keep a fully charged battery fully charged and to provide all the power for the car equipment.
The alternator charge rate is regulated by a voltage regulator. Because the alternator output is connected to the battery, the alternator and battery voltage will be the same and the voltage regulator monitors that voltage.
The lower the battery voltage the more output the alternator will produce in order to correct the situation but because a lead acid battery has a high internal resistance to accepting a charge the terminal voltage will quickly rise to the alternator regulated voltage and fool the alternator into thinking the battery is fully charged when the output will drop to the order of just a couple of amps.
Switch on the headlights or a similar load that will lower the battery voltage and the alternator will increase it's output again - but only by the amount of current the headlamps or other load is consuming.
It matters not what the alternator rated maximum output is, it is designed to provide only the necessary current and no more.
The only time an alternator should ever need to produce maximum output is when on a dedicated testbed and then only for a short duration to avoid damaging the unit. Testing the current output on a modern vehicle is not recommended except for the regulated voltage testing and a rule-of-thumb output test where all equipment is switched on and the engine speed raised while the battery voltage is monitored.
Most modern alternators use an internal voltage regulator but a few systems use a separate voltage regulator. No alternator rebuild would be complete without a regulator test and probably a new or replacement regulator, which is where the majority of charging system problems are, or the brush gear.
Assuming the wiring is ok, no alternator should suffer any harm if the voltage regulator and auxilliary diodes (if fitted) are in good order though fitting a defective or a discharged battery can cause it to overheat and be damaged.
The alternator usually just about stops producing an output when the battery voltage is in the region of 14.5/14.8 volts.
Your description indicates the voltage regulator is not working correctly - unless 40 amps was being consumed by the car equipment the alternator should not have been producing 40 amps.. I suggest you also have your battery tested
Did you have the charging system and battery checked first before you started throwing parts at the car? Because I'm start to think that its in the wiring from the alternator to the battery (if the alternator was tested good). the symptoms are pointing to a bad alternator with the car not running after a jump. (the car is running off the battery which doesn't have much a charge and then it dies when the battery voltage drops too low). I would bet that your ignition wire to the alternator is bad (or signal wire) which tells the alternator the car is on and to start charging. I had a similar issue with my Honda and only a technician who rebuilt alternators was able to show me how to test it. Seems like you have a similar issue. Have the alternator and battery tested at any local Autozone and if they both test good I would start with the wiring as I suspect this is the issue you have. One of your alternator wires is the ignition wire which puts 12volts to the alternator (turning on the charging) to allows it to put out voltage to your battery.
You may have a bad alternator, when the alternator isnt charging this will also turn battery light on, have the cars charging system tested, this will tell you if the alternator is charging, hope this helps.
No your alternator is not longer working correctly. It could be as simple as a broken alternator drive belt. Open the hood an see if you see any naked pulleys. If the belt is in place then you most likely with have bad alternator. NAPA and Autozone have stores that can test your old alternator. Con comeone into removing it and have it tested. If it is bad get a REBUILT one. A new one will cost a small fortune!
never mind testing if when you start the car you are getting them voltages then fit a new alternator and quick before you burn out the ECU ,the regulator has packed up end of story ,change alternator now ,NEW not a scrappy one from scrapyard,and stop try to confuse the issue with something you do not know ,no voltage leaving the alternator should not exceed 14.7v
ok, the solution for it is very simple.
get it to autozone and ask them to do an alternator test to see if the alternator is producing energy if you are the kind of person that doesn't know anything about cars.
if you are a semi-skilled person then get a voltimeter and test the battery with the car on. and the positive lead with positive and negative with negative, it should read about 14 or more.
if you go to autozone or o'reilly then ask to see the voltage on their little tester. and if you see a voltage of around 14 then you can be sure that the problem is not your alternator.
if your alternator test fine then the next step would be to check your battery. turn the headlights on with car off, then voltage should not go below 10 volts when you plug the voltimeter.
You need to replace the battery to start with. you cannot test the charging system with the battery the way it is or you will get a false reading. Once you replace the battery, you can then test your charging system to see if the alternator is causing the problem. If its charging more than 14.8 -15 volts, its too much and you will need to replace the alternator.
you probably had one of the diodes in the alternator burn out...go to auto parts store and have them test the charging system or use a multimeter if you have one, normal, engine running voltage should be around 14 volts, if below 12.6 the alt. is not charging and needs replacing. Enjoy
generally, the battery lite will come on due to a charging problem. 1st ck to make sure belt is on and tight. 2nd if you have volt meter, with vehicle running, ck voltage at battery terminals. should be over 13.5 volts, if not, verify there is 12 volt supply to large red wire at alternator. if there is voltage at alternator, but less than 13.5 across battery with it running, replace alternator