New Alternator Died Instantly

The fact it was very hot indicates a likely short-circuit. Did you wire the alternator up correctly?

the wiring was very simple one plug that can only go in one way and one other wire to connect with a nut. so yes i think so is there a way i could have messed that up ?

Does it have an integral voltage regulator?

not sure what that is where would i find that. thanks for the reply

It's an integrated circuit sold as part of the alternator rather than as a separate box. It's heat-sinked to the alt. case.

Never mind the internal regulator, why did the original die? How's your battery? Does the car start now, and run without the alternator in the circuit? Knowing the vehicle type, etc, etc, etc wouldn't hurt the analysis. Details are welcome here.

the car is a 2002 mazda protege the original was whining for a while the the car died while my daughter was driving. i jump started it with my car and she was able to drive 3 miles home

If the car died while Princess was mobile, that means that the battery, and the alternator were out to lunch.

I'd put a full charge on the battery with a good charger before I installed the next test alternator.

Sorry I couldn't be of any real help. I could tell you stories about my daughter's car with water in the gas tank. Drove me crazy.

Good luck!

Let us know what type of vehicle you have year and make. Your description makes it sound as if it has a separate voltage regulator, in which case there could be A problem with the voltage regulator.

The large wire that connects to the back of the alternator is typically 12 V positive connection. If you have a meter you can check and confirm that you are getting somewhere in the neighborhood of 12 V from that lead to ground, provided your battery is charged.

This wire is typically hot all the time, although on some vehicles it may not be if you do not get a voltage reading to ground turn the ignition switch on, the vehicle does not have to be running.

If you still do not get a voltage reading , set the meter for continuity if you have continuity from the wire that connects to the back of the alternator to ground you have a dead short, and that could easily fry a alternator.

It might be possible for defective voltage regulator to fry alternator, but I would think it is more likely that either you have a dead short on the positive lead, or your replacement alternator was defective.

which wire would be the ground one of the two in the plug connection

Do not worry about the to plug connection, go directly to the body or the negative terminal of the battery. You might also try physically inspecting the large wire from the back of the alternator if you can trace it.

It sounds like the replacement alternator was trying charge up a very run down battery. As has been suggested in a case like this, the battery should be charged with a charger, not with the alternator. The alternator will try its best to supply power to recharge a severely challenged battery, and will often burn up its diodes in the process.

Especially if the battery is low on liquid or has shorted cells. Pull the battery and have it analyzed at the auto supply. If it is bad it could take out a charger like it did the alternator.

If the alternator is from a supply that offers 'lifetime' replacement, I would get that exchanged first. Then take in the battery.

You need to validate the insulation on the positive battery cable in those hard to see places, since the excessive amps may have done some melting you didn't notice before. You might have a short after all to add to the confusion. CJM

I have an '85 Mustang GT with a 4 BBL CARBURETOR.. NOT FUEL INJECTED. My brother gave it to me with a dead battery, bad voltage regulator, bad alternator, holes rusted in the gas tank and a cop car motor. I replaced all that stuff with NEW replacements, drove 300 miles and by the time I got near my city, I noticed that the lights on the dash were dimming and the radio didn't work so good anymore and so forth. I got home, tested the output from the alternator, and got .25 volts on the stator connector, nothing on the phase, and nothing on the positive post. This is with everything disconnected from the alternator and the car running. I got a replacement, same thing. I got another replacement.. same thing.. what the hell.. I though these things were supposed to put out a couple volts. I tried running it for FIFTEEN MINUTES at 2000 RPM and still nothing comes out of the alternator. I'm SURE 3 Alternators can't be bad in a row, and since I'm volt testing them on the car NOT CONNECTED, with the car running, I should see voltage, right? The most I've seen is a half a volt from the stator connector. Maybe a quarter volt from the phase line and nothing from ANY of the battery connectors.. WTF?!!?!?!

Oh, save me a few rants and don't tell me it's a short or faulty wiring. Why would their (Vato-zone) store's machine tell me all these alternators are good out of the car, but when I bolt the alternator to the engine, put on the belt, start the car and try reading output I get nothing, or voltage so minimal I'm sure it's not doing the job. What do I do now? Please send private replies to emhartain at aol dot com. I hate registering for new sites. each new registry gives me 2 new spam mails.. no thanks.

Is the voltage regulator correctly wired and in good order?

You need to check your battery and also your wiring for resistance between the alternator and the battery, both positive cables and the ground path! What isd happening to you is caused by resistance in the wiring causing the alt to go into full output charging and that kills the sucker!

Could be the battery and here's why I say that.

A few years ago my wife bought a car off the internet. It sat in storage for a year until we flew down to get it. (Montana to Florida) Of course the battery was dead so it was jumped and we bought a new one. We had no problems with the alternator until we were about 10 miles down the road from buying the new battery. It showed a big discharge and the car died (in the middle of a huge intersection). I ran up the street to an auto parts store and bought a new battery. The car started and ran but no charge from the alternator. I bought a new alternator and put it on and everything was fine.

I found a warning in the alternator box which said a bad battery can cause an alternator to fail. I hadn't ever thought that was possible before but... So I took the first new battery back to the store and told them what had happened. I got the usual of "our batteries won't do that but we'll check it to show you". When I returned later, the man said the battery was bad and gave me another.

I have no proof, but I really think that battery had some major problems and took out the alternator when it went bad. (I think it fell apart on the insides and shorted out).

Randy

You let the smoke out eh? Alternators are good until they fail

Take it back, sometimes an alternator will last years others minutes or no time at all.

That wouldn't surprise me at all. Recently went through this with my BMW. Alternator quit, replaced it and it lasted two days (was putting out 18volts to the battery, replaced the battery, took the alternator back and got another. This one lasted to the end of the block (no output). Big label on both of the alternators "Remanufactured in Mexico". Ended up taking it to a shop where he put an OEM alternator on it for about $50 more than the rebuilt ones. You can measure battery voltage with the car running, anything less than about 13 volts and your alternator isn't charging, should be around 14-14.5 volts but could be as high as 15.5-16. You can also measure voltage on the output lead on the alternator, should be about the same thing. Other posts are correct that I believe a bad battery can make the alternator go bad. Good luck.

TAKE THE CAR TO A QUALIFIED REPAIR SHOP.

I have been down this road, with a generator and defective voltage regulator, burned out the generator in less then 30 miles and drove home on the battery with the headlights on. After you burn up enough parts that no one will sell to you with a warranty or replace them. Also once had a VW that the regulator wouldn't keep the battery charged if drove at night with headlights on.

This is a tricky thing to set up right and can be very expensive, over and over again, if done wrong.

I ran into this decades ago. If there is an open in the power output lead, the system will impose a higher and higher field voltage on the alternator, trying to 'charge'. As this voltage goes too high, the coil burns out. This has nothing to do with the battery condition or state of charge. Any time I have a 'fail to charge' I do a continuity check on the lead from the alternator to the battery. Look for a voltage dop while the engine is running, or resistance if you unhook the fat wire. Often there is a wire problem before the alternator has died. A separate 3mm to 5mm wire directly from the alternator (fat) terminal to the battery is always a good idea for an older car in a salty part of the world, especially if you have found 'resistance' or an intermittent or a solid open....

You should do a load test on the battery. A shorted cell in the battery can lead to alternator failure. Placing a new alternator in without testing the battery could cost you another alternator.

Over the past 50 years, I have had many batteries develop a failed cell. This shows up as needing high charging currents, and poor starting. (Another sign: Charging with a 5-to-10 amp 120VAC charger yields 10 volts or so even after hours...) None of these events has harmed the charging circuit involved. A good charging system will survive a failed battery. A good charging system will just put out its rated current (at 11 volts) happily as long as the engine is above idle. A healthy but largely discharged battery will not cause a charging system failure either.

It is always worth doing a load/voltage or open circuit voltage test on a battery before installing it. If it has failed do not install it, primarily because it will waste your time as a repairer, and not get your wife home from her next trip! No one should replace a component without proving that it is defective. Too many commercial repairers replace battery, then alternator, then starter. Sad if the only original problem was imperfect wiring.

i would like to express my doubts .look am an electrical engineeer so i dont know nothing of automobiles and i think here all are automobile experts.

the main purpose of the generator used i guess would be to charge the battery.if it is true ,then the generator should be of DC type, and probably a shunt generator.then please dont call that generator -alternator.because ac generators are only called alternators as they gives an alternating current.

shunt generators generates voltage and current only if the shunt field winding have some residue magnetic flux.if you connect the terminals of the battery which may contain some charge ,then the residue flux gets wipped off .then the geneator will lay dead.in that case dont worry- connect a fully charged battery across the generator after disconnecting the rotating armature part.let the current flow through the shunt winding only.

secondly -use thicker wires to connect the generator to the battery.and use thicker connectors and make sure all is of good quality.

check whether they are made in china.if so dont waste your time in repairing and next time make sure they r not made in china.

lastly ask the car manufactures to use seperatly exited generators instead of shunt generators .for seperatly exited generators there will be four terminals.first you connect the field wire to the battery if it is charged ok.then if you have time rotate the gnerator and check the polarity of the the wires using a voltmeter or multimeter .then connect the that wires to the battery.if the generator is not charging the battery inter change the connections of any one pair of wires ok.so i think seperatly exited generators r the best.also the shunt generators can be converted to seperatly excited generators simply by taking out the terminals of the field winding ,instead of connecting it internally.so no additional expenses.

thanking you

Modern automobiles use alternators which generate AC voltage; the voltage is rectified to DC before distribution to the automobile's electrical system.

You should remove each of the cables from the battery and clean both the seat on the battery and the face of the cable connection. If you do not have a sound connection, you will not get continuous current flow from cable to battery nor in the other direction.

I remember a seasoned auto mechanic telling me that, in order for an automotive alterntor to produce current, it needs an exciting current. If your battery is either dead to nearly so, there is not enough current to excite the alternator to provide operating current. I also was told that an alternator is not designed to recharge a run-down battery, only to maintain an already sufficient charge and to support in-use demands from electrical accessories. This advice was in response to my queries regarding frequent battery failures, and I was advised to regularly put a full charge on the battery using a charger on slow charge rate. This was the result of having various accessory devices that were not wired through the ignition switch and thus drew small currents even while the vehicle was not running, resulting in many cycles of discharge/recharge that eventually caused enough precipitate in the battery to short the plates.

I want to thank all of you for all your responses. After charging the battery over night I put the new alternator in and everything is working fine. The one that i took back to autozone after testing was deemed ok. Therefore I would say the battery was depleted and over loading the new alternator or indeed there was some problem with the first one I received. Thanks again you guys are the best Trace

Thank you for the recap...and have a good day

Sounds like you have a short somewhere, I recommend bringing it in to a competent auto mechanic who is knowledgable in the electrical system of your car and has the proper equipment to find the short. Good luck

The replies you have received are missing a big clue. You put in a new battery and its got hot. You have a direct short start looking for burnt wire or wires. some where in the vehicle a battery cable or a wire in the service wire harness has a bare spot and is touching the body or a ground wire. After you have looked along the battery positive wire to the starter, and have not found the problem. remove the positive wire from the starter and see if the wires or battery gets hot. Follow the other wires to there end and they may very well be under the dash. do not rule out a bad starter as they can short out as well. You may very well may need to remove outer harness insulation around the wiring in the harness to find the short.

There is a test that you can do. It requires a voltage test meter with an amp setting. you will be doing an amperage draw test with the electrical system off. The dial should have a 10a setting. Remove the positive wire from the battery if not already off. put the test leads from the tester one on the battery like the black lead and the other the red on the positive wire and see what the current draw is if its any thing above 500 milliamps the amount the clock takes you still have a problem. If you can't find the bad wire remove fuses and relays until the amp meter stops showing a high reading. replace each if they have no effect on the meter. When you find the circuit with the short you can fix it. it may take a lot of looking, poking and prodding.

IF your auto has the head lights and tail lights come on with the key switch look for bad wire or bulb there as will. But not likely the problem. The key switch can be bad ?

a hot battery and or a hot alternator with the engine off means a short or open circuit and have a voltage flow.

good luck

again i have a sugession .i shall admit nowadays alternators which produce ac is used .the output is rectified and dc is given out.now if we connect this to a dicharged battery,, what happenes is ,the battery offers very low current path ie a shortcircuit and damages the alternator.so burned wires may not be found.

i shall explain when battery have some charged ,there will some voltage across its terminal which would come across the alternator.the alternator terminal voltage should be more to charge the battery.if there is a rectifier the reverse flow of charge back to alternator may not happen.but the net charging voltage -which is the driving force for charging the battery will be the difference between these to voltages.ie voltage across alternator and battery .if the voltage across the battery is very low then a larger current will flow to the battery ,which heats up the alternator and may even be damaged.

but dont worry there is still a solution.use a proper resistance in series with the alternator .ie between alternator and battery.this helps reduce the current magnitude and there by prevents the damage of alternator. may be a 100ohm resistance can be used.ofcourse this may have some effect in efficency.but frequent damage to alternator and battery can be avoided.remember to use a higher wattage rated resistance.

i have a new design idea for the automobile alternator design.this consists a battery alternator set plus some electronic circuits.all in one unit.here constant current method for charging the battery is employed. if the battery is low still the current from the alternator wont increase ,it will be around a predetermined value only.the alternator used will a rotating field type and the field used will be a permanant magnet type.plus a electromagnet will be there connected using a centrifugal switch.the battery charging will only be started if only the output voltage raises above a preset value.look please the idea of using double type field is a new invension.please dont copy it.ok .

Several years ago I bought what I thought was a new Alternator only to find out it is a rebuilt one. Right of the shelf it died, some time they don't get them right. I took it back to the place and they tested it and it worked just fine. Turns out the test they did does not put the same stress of a load as my pickup does so yeah it passed. I asked for different one, installed it and never had a problem with it again.

Good luck

Lee

I had the same thing happen, got a bad one off the shelf. It was working so hard it squealed the belt.

Had it checked on the the test machine in the auto parts store, they said it was OK. Took it back a 2nd time for a re-test and noticed a test-board LED was lit that was missed by the tech, and asked him to check the machine manual. It turned out that 1/2 the diodes were burned out.

I presume the rebuilding crew missed the diode problem, though it was cleaned up real nice. With 1/2 of the diodes bad, it was under powered for the demand placed on it.

I guess the thing to learn from that is that some 'new' parts can have a problem, and the people working in the auto parts store are not perfect either. We need to be alert in our own best interest. That's pretty much true in a lot of fields of endeavor. CJM