Bad alternator?battery?
01-18-2018, 10:15 AM
#1
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Bad alternator?battery?
Iv been having an issue where I’m getting the same output from the alternator as the battery has so , when the battery says 11.5 the alternator says the same? And it isn’t charging my battery, I got a new battery and new alternator. Should I get it tested? Am completely lost
01-18-2018, 10:19 AM
#2
Le Mans Master
Iv been having an issue where I’m getting the same output from the alternator as the battery has so , when the battery says 11.5 the alternator says the same? And it isn’t charging my battery, I got a new battery and new alternator. Should I get it tested? Am completely lost
why not get it tested?
Last edited by Cruisinfanatic; 01-18-2018 at 10:20 AM.
01-18-2018, 10:30 AM
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01-18-2018, 11:45 AM
#4
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Sounds like a pretty big current draw somewhere. There are a number of post that describe how to check for current draw in the various circuits.
I assume you re using a digital volt meter to read that indicated 11.5v? Start by charging the battery with the negative cable detached. Once the charging is done, you should see a voltage around 12.5 to 12.6 volts across the terminals.
Re-connect the negative cable and start the engine. What is the voltage output at the large red wire? Should be around 13.8 to 14.5 volts after the engine runs for a minute or so. What is the voltage across the battery terminals?
It probably would be a good idea to take the car to a reputable shop to have the charging system tested. That would include a load test on the battery and an output test of the alternator.
You didn't say what brand of battery or alternator you bought, but there can be a huge difference in quality and performance depending on the brand.
I assume you re using a digital volt meter to read that indicated 11.5v? Start by charging the battery with the negative cable detached. Once the charging is done, you should see a voltage around 12.5 to 12.6 volts across the terminals.
Re-connect the negative cable and start the engine. What is the voltage output at the large red wire? Should be around 13.8 to 14.5 volts after the engine runs for a minute or so. What is the voltage across the battery terminals?
It probably would be a good idea to take the car to a reputable shop to have the charging system tested. That would include a load test on the battery and an output test of the alternator.
You didn't say what brand of battery or alternator you bought, but there can be a huge difference in quality and performance depending on the brand.
01-18-2018, 02:08 PM
#5
Safety Car
Hello there,
I would follow the advise of the previous poster about checking to be sure that your car is in fact not pulling the current out of the battery that fast. If there was a big short in your car usually there would probably be smoke. Lets hope that the problem is limited in the Alternator charging circuit of your car.
How old is the battery in question? What brand is the battery? When did you last "completely" charge it while disconnected from the car? What is the voltage of the battery with nothing connected to it?
What happens to the voltage after the battery is connected to the car for an hour of no-use and no lights or other loads turned on?
Batteries can develop internal shorts and this is a normal way for them to get to a recycling yard. If the battery has a short internally the voltage should go down with nothing connected. If your battery is self discharging rapidly it can be dangerous so remove it from the car and put outside until it can be safely disposed of.
If your battery is fully charged then hook it up to the car and then turn on the headlights for about 10-15 minutes and check the batteries voltage again. If the voltage is still up in the 12+ range then the battery is not the problem. If it drops below the 12 volt mark then the battery is going to be suspect.
If you have access to a Volt Ohm meter with the "Min-Max" setting on it connect the meter to the battery and try starting the car. If the voltage drops below 9 Volts then it is time to buy a battery.
With your battery in the car and the car is started the alternator should push the voltage up to close to 14.5 volts. If your car is running and the voltage is not above 12 volts then it is either the alternator or the wiring on the car. Check the wiring from the alternator to the battery Positive (+) side, you should see the same voltage when measuring from the alternator out to Battery Negative as you do from the battery Positive (+) to the Battery Negative (-). Check from battery Positive (+) to the engine metal (which is supposed to be grounded) and you should still see the full voltage.
After all these years the battery connections probably have corrosion and that causes resistance which makes heat. Clean the battery terminals with a wire brush and then clean every connection you see that has any corrosion on it. The trick here is to make the path for the current to be as clean as possible.
Let us know how it goes and we here on the Forum can try to help you get your voltages back in the normal range so you can enjoy that Corvette of yours!
P.S. In the future please identify what year and model Corvette you have, it really helps us out here if we have more information...
I would follow the advise of the previous poster about checking to be sure that your car is in fact not pulling the current out of the battery that fast. If there was a big short in your car usually there would probably be smoke. Lets hope that the problem is limited in the Alternator charging circuit of your car.
How old is the battery in question? What brand is the battery? When did you last "completely" charge it while disconnected from the car? What is the voltage of the battery with nothing connected to it?
What happens to the voltage after the battery is connected to the car for an hour of no-use and no lights or other loads turned on?
Batteries can develop internal shorts and this is a normal way for them to get to a recycling yard. If the battery has a short internally the voltage should go down with nothing connected. If your battery is self discharging rapidly it can be dangerous so remove it from the car and put outside until it can be safely disposed of.
If your battery is fully charged then hook it up to the car and then turn on the headlights for about 10-15 minutes and check the batteries voltage again. If the voltage is still up in the 12+ range then the battery is not the problem. If it drops below the 12 volt mark then the battery is going to be suspect.
If you have access to a Volt Ohm meter with the "Min-Max" setting on it connect the meter to the battery and try starting the car. If the voltage drops below 9 Volts then it is time to buy a battery.
With your battery in the car and the car is started the alternator should push the voltage up to close to 14.5 volts. If your car is running and the voltage is not above 12 volts then it is either the alternator or the wiring on the car. Check the wiring from the alternator to the battery Positive (+) side, you should see the same voltage when measuring from the alternator out to Battery Negative as you do from the battery Positive (+) to the Battery Negative (-). Check from battery Positive (+) to the engine metal (which is supposed to be grounded) and you should still see the full voltage.
After all these years the battery connections probably have corrosion and that causes resistance which makes heat. Clean the battery terminals with a wire brush and then clean every connection you see that has any corrosion on it. The trick here is to make the path for the current to be as clean as possible.
Let us know how it goes and we here on the Forum can try to help you get your voltages back in the normal range so you can enjoy that Corvette of yours!
P.S. In the future please identify what year and model Corvette you have, it really helps us out here if we have more information...
Last edited by ctmccloskey; 01-18-2018 at 02:10 PM. Reason: ADD P.S.
01-19-2018, 03:02 AM
#6
Melting Slicks
Sounds like a pretty big current draw somewhere. There are a number of post that describe how to check for current draw in the various circuits.
I assume you re using a digital volt meter to read that indicated 11.5v? Start by charging the battery with the negative cable detached. Once the charging is done, you should see a voltage around 12.5 to 12.6 volts across the terminals.
Re-connect the negative cable and start the engine. What is the voltage output at the large red wire? Should be around 13.8 to 14.5 volts after the engine runs for a minute or so. What is the voltage across the battery terminals?
It probably would be a good idea to take the car to a reputable shop to have the charging system tested. That would include a load test on the battery and an output test of the alternator.
You didn't say what brand of battery or alternator you bought, but there can be a huge difference in quality and performance depending on the brand.
I assume you re using a digital volt meter to read that indicated 11.5v? Start by charging the battery with the negative cable detached. Once the charging is done, you should see a voltage around 12.5 to 12.6 volts across the terminals.
Re-connect the negative cable and start the engine. What is the voltage output at the large red wire? Should be around 13.8 to 14.5 volts after the engine runs for a minute or so. What is the voltage across the battery terminals?
It probably would be a good idea to take the car to a reputable shop to have the charging system tested. That would include a load test on the battery and an output test of the alternator.
You didn't say what brand of battery or alternator you bought, but there can be a huge difference in quality and performance depending on the brand.
Check voltage with ignition on engine off, when you start the car it should go up a couple of volts.
Now that depends on how your battery is, if its not 12 volts you may never see much of a jump. Sounds like a bad battery, they don't last long a few years maybe but you should see some voltage rise when the engine is started.
If the voltage doesn't go up right away the alternator may not be charging.
01-19-2018, 01:28 PM
#7
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Hello there,
I would follow the advise of the previous poster about checking to be sure that your car is in fact not pulling the current out of the battery that fast. If there was a big short in your car usually there would probably be smoke. Lets hope that the problem is limited in the Alternator charging circuit of your car.
How old is the battery in question? What brand is the battery? When did you last "completely" charge it while disconnected from the car? What is the voltage of the battery with nothing connected to it?
What happens to the voltage after the battery is connected to the car for an hour of no-use and no lights or other loads turned on?
Batteries can develop internal shorts and this is a normal way for them to get to a recycling yard. If the battery has a short internally the voltage should go down with nothing connected. If your battery is self discharging rapidly it can be dangerous so remove it from the car and put outside until it can be safely disposed of.
If your battery is fully charged then hook it up to the car and then turn on the headlights for about 10-15 minutes and check the batteries voltage again. If the voltage is still up in the 12+ range then the battery is not the problem. If it drops below the 12 volt mark then the battery is going to be suspect.
If you have access to a Volt Ohm meter with the "Min-Max" setting on it connect the meter to the battery and try starting the car. If the voltage drops below 9 Volts then it is time to buy a battery.
With your battery in the car and the car is started the alternator should push the voltage up to close to 14.5 volts. If your car is running and the voltage is not above 12 volts then it is either the alternator or the wiring on the car. Check the wiring from the alternator to the battery Positive (+) side, you should see the same voltage when measuring from the alternator out to Battery Negative as you do from the battery Positive (+) to the Battery Negative (-). Check from battery Positive (+) to the engine metal (which is supposed to be grounded) and you should still see the full voltage.
After all these years the battery connections probably have corrosion and that causes resistance which makes heat. Clean the battery terminals with a wire brush and then clean every connection you see that has any corrosion on it. The trick here is to make the path for the current to be as clean as possible.
Let us know how it goes and we here on the Forum can try to help you get your voltages back in the normal range so you can enjoy that Corvette of yours!
P.S. In the future please identify what year and model Corvette you have, it really helps us out here if we have more information...
I would follow the advise of the previous poster about checking to be sure that your car is in fact not pulling the current out of the battery that fast. If there was a big short in your car usually there would probably be smoke. Lets hope that the problem is limited in the Alternator charging circuit of your car.
How old is the battery in question? What brand is the battery? When did you last "completely" charge it while disconnected from the car? What is the voltage of the battery with nothing connected to it?
What happens to the voltage after the battery is connected to the car for an hour of no-use and no lights or other loads turned on?
Batteries can develop internal shorts and this is a normal way for them to get to a recycling yard. If the battery has a short internally the voltage should go down with nothing connected. If your battery is self discharging rapidly it can be dangerous so remove it from the car and put outside until it can be safely disposed of.
If your battery is fully charged then hook it up to the car and then turn on the headlights for about 10-15 minutes and check the batteries voltage again. If the voltage is still up in the 12+ range then the battery is not the problem. If it drops below the 12 volt mark then the battery is going to be suspect.
If you have access to a Volt Ohm meter with the "Min-Max" setting on it connect the meter to the battery and try starting the car. If the voltage drops below 9 Volts then it is time to buy a battery.
With your battery in the car and the car is started the alternator should push the voltage up to close to 14.5 volts. If your car is running and the voltage is not above 12 volts then it is either the alternator or the wiring on the car. Check the wiring from the alternator to the battery Positive (+) side, you should see the same voltage when measuring from the alternator out to Battery Negative as you do from the battery Positive (+) to the Battery Negative (-). Check from battery Positive (+) to the engine metal (which is supposed to be grounded) and you should still see the full voltage.
After all these years the battery connections probably have corrosion and that causes resistance which makes heat. Clean the battery terminals with a wire brush and then clean every connection you see that has any corrosion on it. The trick here is to make the path for the current to be as clean as possible.
Let us know how it goes and we here on the Forum can try to help you get your voltages back in the normal range so you can enjoy that Corvette of yours!
P.S. In the future please identify what year and model Corvette you have, it really helps us out here if we have more information...
I figured it out! The wires connecting into the bottom of the alternator were very looses and I cleaned them up and and works perfect now! Putting out 14.5 volts. Thank you guys for you’re suggestions