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The battery runs all electrical components, not the alternator. The only purpose of the alternator is to keep the battery charged. The amount of current going into the battery is controlled by the voltage regulator which is internal in the alternator. The battery is maintained at about 12.6 volts.
The battery runs all electrical components, not the alternator. The only purpose of the alternator is to keep the battery charged. The amount of current going into the battery is controlled by the voltage regulator which is internal in the alternator. The battery is maintained at about 12.6 volts.
If the motor runs when jump-started, but not without a jump start, it means that the battery is not supplying enough current for the ECU and the starter to work. The alternator does in fact supply all the current needed for the motor and all the electrical components to work when the battery is not holding voltage. After a jump start you can run the motor all day long, even if the battery does not hold a charge. But the soonest you turn the motor off, it won't start again without a jump start.
If it's the alternator, you wouldn't be able to drive it at all
Quote:
Originally Posted by adriver
Yes that's true for the OP, but its only required if you have fuel injection. I learned that one too.
I had a china made lighter socket power cable for my gps break while using it once. The plug that goes in to the gps came off (the mini usb head), and I heard a pop through the stereo. It took about an hour for my battery to go from perfect to completely dead. So dead that the fuel injection was sputtering and couldn't keep up, and using the window switch was near killing it, it eventually lost all the juice and couldn't run the fuel injection then died. I replaced the alternator at a rest stop, got a (5 minute) jump, and was good to go.
Sorry, as to the bolded, that's not true; Although not advisable, it can be driven for the Reserve Capacity of the battery, until it is run down and stone dead. This is called "cycling" the battery and isn't good, but it is why the battery light lights when the alternator fails; because you then run on the battery.
A small car with no electrical load on a hot day (? Cold day too, I suppose) can run for a few hours approximately off just a battery, if you had to maybe get to work with no alternator. Not adviseable, simply being technical here.
I've a few cars with non-charging alternators, so I speak from experience on this.
If it's the alternator, you wouldn't be able to drive it at all
Sorry, as to the bolded, that's not true; Although not advisable, it can be driven for the Reserve Capacity of the battery, until it is run down and stone dead. This is called "cycling" the battery and isn't good, but it is why the battery light lights when the alternator fails; because you then run on the battery.
A small car with no electrical load on a hot day (? Cold day too, I suppose) can run for a few hours approximately off just a battery, if you had to maybe get to work with no alternator. Not adviseable, simply being technical here.
I've a few cars with non-charging alternators, so I speak from experience on this.
Not true on a cold day, nor on a day where you are driving with the AC and the blower ON. If the alternator malfunctions, the battery lasts perhaps 20 minutes on a lucky day if you have the lights, and the blower running. All depends on the battery capacity status versus the load, battery's age, and temperature to name a few. On a new and fully charged battery you may have more time, however. On a hot day the radiator's fan also draws a lot of power, which in turn discharges a battery if the alternator is not working.
By the way, old automobiles used a very small amount of battery power if you turned the lights and the AC/Heater blower off. Just about everything was manual. But new automobiles have electric cooling fans, electric gages, an ECU, electric fuel injection system, ABS that becomes active when you touch the brake pedal, and so on.
Not true on a cold day, nor on a day where you are driving with the AC and the blower ON. If the alternator malfunctions, the battery lasts perhaps 20 minutes on a lucky day if you have the lights, and the blower running. All depends on the battery capacity status versus the load, battery's age, and temperature to name a few. On a new and fully charged battery you may have more time, however. On a hot day the radiator's fan also draws a lot of power, which in turn discharges a battery if the alternator is not working.
By the way, old automobiles used a very small amount of battery power if you turned the lights and the AC/Heater blower off. Just about everything was manual. But new automobiles have electric cooling fans, electric gages, an ECU, electric fuel injection system, ABS that becomes active when you touch the brake pedal, and so on.
Quote:
Originally Posted by Ollie4
If it's the alternator, you wouldn't be able to drive it at all
Sorry, as to the bolded, that's not true; Although not advisable, it can be driven for the Reserve Capacity of the battery, until it is run down and stone dead. This is called "cycling" the battery and isn't good, but it is why the battery light lights when the alternator fails; because you then run on the battery.
A small car with no electrical load on a hot day (? Cold day too, I suppose) can run for a few hours approximately off just a battery, if you had to maybe get to work with no alternator. Not adviseable, simply being technical here.
I've a few cars with non-charging alternators, so I speak from experience on this.
Yes that's true,
I should clarify, what I meant was you't can drive on it regularly. You can, but only until you kill the battery. IT HAPPENED TO ME. Mine went from no problems at all, then had my alternator get fried while driving. It was completely dead about an hour later, and 15 minutes of that I was pulled over and truck was shut off.
The 14.2v with the engine running proves the alternator is working.
Really! If the alternator is putting out 13.8 to 14.2 volts it is working. Nothing else matters. The trouble is elsewhere. Likely bad battery or bad battery connections.
If Its the alternator, a jump won't help you because the battery is run so down it won't be able to start the car except after charged up for a long time.
Say what? If the cables are stout and well connected they will[provide most of the current the starter needs.
Quote:
Originally Posted by Ollie4
Battery light is usually, but not always, on if it is the alternator.
Got a multimeter? If so, you don't need a load tester...
*edit: Looked at your nunbers. Alternator at maximum output when its running, looks good.
Sounds like a weak battery to me.
That 14.2 volts is good, but is that with or without headlights, Ac, etc? If without, it might drop into the discharge range with increased electrical load.
Don in Austin
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