Volt meter staying at +40
08-26-2018, 01:11 PM
#6
Race Director
A minute or two? Or for more than 5 or 10 minutes? Get, borrow, buy a voltmeter. Pic of top of alternator. I think 69 is first year volt reg was built into alternator. And that is amps, not volts... Volts should be 13.5 to 14.5 when running. Over 15 it is overcharging the battery and cooking it.
Last edited by derekderek; 08-26-2018 at 01:13 PM.
08-26-2018, 02:19 PM
#7
Melting Slicks
That gauge is actually a galvanometer which is installed in a manner that shows both the strength and direction of a small current (amps) in a circuit. It does not measure volts.
During cranking the starter is drawing amps and the gauge should go negative to some extent showing the relative discharge from the battery.
Once the engine is running the alternator recharges the battery which should make the amp meter go positive until the battery is fully charged (+40 is a bit high but depends on battery condition).
Once the battery is fully charged the amp meter will show zero or just a bit positive of zero demonstrating that the battery, alternator, and charging system are "happy".
How long the battery takes to recover to full charge from starting is dependent upon the battery age, condition, temperature, usage, etc.
In the best case the battery recovers very quickly (think new/fully charged battery and quick start) and the gauge goes zero in a very short time - minutes.
If the car has been sitting for weeks/months and the battery is weak (or you just jump started a dead battery) the recovery time can be significant - 15-30 min until the battery is topped off.
If you have a constant negative reading or constant positive reading it indicates a problem with your charging system that should be checked.
Last edited by Hammerhead Fred; 08-26-2018 at 02:28 PM.
08-26-2018, 02:53 PM
#8
Race Director
Member Since: Apr 2007
Location: South Western Ontario
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Check the main power wire from the starter solenoid to the horn relay. The ammeter leads connect to this wire by the firewall and on the horn relay. The ammeter could do as you see if the main wire between the 2 ammeter leads is damaged or has a poor connection.
08-27-2018, 10:54 AM
#9
That gauge is actually a galvanometer which is installed in a manner that shows both the strength and direction of a small current (amps) in a circuit. It does not measure volts.
During cranking the starter is drawing amps and the gauge should go negative to some extent showing the relative discharge from the battery.
Once the engine is running the alternator recharges the battery which should make the amp meter go positive until the battery is fully charged (+40 is a bit high but depends on battery condition).
Once the battery is fully charged the amp meter will show zero or just a bit positive of zero demonstrating that the battery, alternator, and charging system are "happy".
How long the battery takes to recover to full charge from starting is dependent upon the battery age, condition, temperature, usage, etc.
In the best case the battery recovers very quickly (think new/fully charged battery and quick start) and the gauge goes zero in a very short time - minutes.
If the car has been sitting for weeks/months and the battery is weak (or you just jump started a dead battery) the recovery time can be significant - 15-30 min until the battery is topped off.
If you have a constant negative reading or constant positive reading it indicates a problem with your charging system that should be checked.
During cranking the starter is drawing amps and the gauge should go negative to some extent showing the relative discharge from the battery.
Once the engine is running the alternator recharges the battery which should make the amp meter go positive until the battery is fully charged (+40 is a bit high but depends on battery condition).
Once the battery is fully charged the amp meter will show zero or just a bit positive of zero demonstrating that the battery, alternator, and charging system are "happy".
How long the battery takes to recover to full charge from starting is dependent upon the battery age, condition, temperature, usage, etc.
In the best case the battery recovers very quickly (think new/fully charged battery and quick start) and the gauge goes zero in a very short time - minutes.
If the car has been sitting for weeks/months and the battery is weak (or you just jump started a dead battery) the recovery time can be significant - 15-30 min until the battery is topped off.
If you have a constant negative reading or constant positive reading it indicates a problem with your charging system that should be checked.
08-27-2018, 10:55 AM
#10
That gauge is actually a galvanometer which is installed in a manner that shows both the strength and direction of a small current (amps) in a circuit. It does not measure volts.
During cranking the starter is drawing amps and the gauge should go negative to some extent showing the relative discharge from the battery.
Once the engine is running the alternator recharges the battery which should make the amp meter go positive until the battery is fully charged (+40 is a bit high but depends on battery condition).
Once the battery is fully charged the amp meter will show zero or just a bit positive of zero demonstrating that the battery, alternator, and charging system are "happy".
How long the battery takes to recover to full charge from starting is dependent upon the battery age, condition, temperature, usage, etc.
In the best case the battery recovers very quickly (think new/fully charged battery and quick start) and the gauge goes zero in a very short time - minutes.
If the car has been sitting for weeks/months and the battery is weak (or you just jump started a dead battery) the recovery time can be significant - 15-30 min until the battery is topped off.
If you have a constant negative reading or constant positive reading it indicates a problem with your charging system that should be checked.
During cranking the starter is drawing amps and the gauge should go negative to some extent showing the relative discharge from the battery.
Once the engine is running the alternator recharges the battery which should make the amp meter go positive until the battery is fully charged (+40 is a bit high but depends on battery condition).
Once the battery is fully charged the amp meter will show zero or just a bit positive of zero demonstrating that the battery, alternator, and charging system are "happy".
How long the battery takes to recover to full charge from starting is dependent upon the battery age, condition, temperature, usage, etc.
In the best case the battery recovers very quickly (think new/fully charged battery and quick start) and the gauge goes zero in a very short time - minutes.
If the car has been sitting for weeks/months and the battery is weak (or you just jump started a dead battery) the recovery time can be significant - 15-30 min until the battery is topped off.
If you have a constant negative reading or constant positive reading it indicates a problem with your charging system that should be checked.
08-27-2018, 01:50 PM
#13
Burning Brakes
Send the gauge out for rebuild. Mine just started showing -40 when running. The charging system checked out so I sent the gauge out. Now the gauge reads correctly.
Last edited by maj75; 08-27-2018 at 01:51 PM.
08-27-2018, 04:23 PM
#14
Melting Slicks
The dash gauge should be reading something positive immediately after starting the engine and settle back toward zero after several minutes (+40 is fine initially).
Again, the dash gauge is showing AMPS and your gauge at the battery is reading VOLTS.
I don't see where you have an issue yet.
What problem are you trying to solve???
Last edited by Hammerhead Fred; 08-27-2018 at 04:24 PM.
08-27-2018, 04:41 PM
#15
The gauge stays at + 40 constantly only goes to 0 when i turn off the car, i had someone put a meter acroos the battery and it seems fine. I am concernd their is a problem with the charging system and dont want to cook the battery.
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Bubbity (10-22-2023)
08-27-2018, 05:11 PM
#17
Team Owner
Check your battery ground cable and the ground cable going from the engine mount to the block. Even if they look good take them off and clean them real good.
If your DMM has a amp setting then just take the power lead off the back of the alternator and put the +lead of your DMM to the output of the alternator and connect the black lead to the wire taken off of the alternator. Make sure your leads on the meter are in the Amp connections and your meter is set to read amps. This puts your meter in series with the current draw and will show exactly what your alternator is putting out in Amps at any given time. When the circuit is "balanced" your meter should read close to zero with a small current draw (+) when running. If you are not running and turn on the interior lights or radio then you should see a small current draw (-).
If your DMM has a amp setting then just take the power lead off the back of the alternator and put the +lead of your DMM to the output of the alternator and connect the black lead to the wire taken off of the alternator. Make sure your leads on the meter are in the Amp connections and your meter is set to read amps. This puts your meter in series with the current draw and will show exactly what your alternator is putting out in Amps at any given time. When the circuit is "balanced" your meter should read close to zero with a small current draw (+) when running. If you are not running and turn on the interior lights or radio then you should see a small current draw (-).
08-27-2018, 06:58 PM
#18
Melting Slicks
So, sounds like the meter is fine.
You're seeing @14 volts at the battery which says the Alt is charging the battery BUT the charging system is never satisfied.
So, either the battery is weak (most likely) and is always calling for a charge - (what's the battery voltage with the car off?)
OR
The Alternator regulation circuit has failed
Usually, If it's putting out the proper voltage then either the internal regulator is bad OR one of the wires in the sensing circuit is disconnected or broken.
08-27-2018, 07:18 PM
#19
Race Director
if it is putting out 14 volts it is not cooking the battery. batt is possibly low and still charging or gauge is off. but 14 volts is correct. that is all gauges read anymore. they don't look at amps.
08-28-2018, 11:12 AM
#20
Race Director
Check your battery ground cable and the ground cable going from the engine mount to the block. Even if they look good take them off and clean them real good.
If your DMM has a amp setting then just take the power lead off the back of the alternator and put the +lead of your DMM to the output of the alternator and connect the black lead to the wire taken off of the alternator. Make sure your leads on the meter are in the Amp connections and your meter is set to read amps. This puts your meter in series with the current draw and will show exactly what your alternator is putting out in Amps at any given time. When the circuit is "balanced" your meter should read close to zero with a small current draw (+) when running. If you are not running and turn on the interior lights or radio then you should see a small current draw (-).
If your DMM has a amp setting then just take the power lead off the back of the alternator and put the +lead of your DMM to the output of the alternator and connect the black lead to the wire taken off of the alternator. Make sure your leads on the meter are in the Amp connections and your meter is set to read amps. This puts your meter in series with the current draw and will show exactly what your alternator is putting out in Amps at any given time. When the circuit is "balanced" your meter should read close to zero with a small current draw (+) when running. If you are not running and turn on the interior lights or radio then you should see a small current draw (-).
When the circuit is "balanced" your meter should read close to zero with a small current charge (+) when running. If you are not running and turn on the interior lights or radio then you should see a small current draw (-).
I would look at your battery cable connections a the battery and on the frame to make sure they are CLEAN and TIGHT and then the alternator (possibly). No need to add more due to the explanations are correct on what to do...and that 14 volts is fine if the battery is low.
DUB
