Originally Posted by dgc333
A failure of the alternator that would result in an over charge would be a very rare occurance.
The output of the alternator is controlled by turning current on and off to the field windings. I don't recall which system you have, pre 69 where there is just one wire connected to the field windings or the 69 up with two wires. This is in addition to the output terminal.
In the pre 69 system one end of the field windings is connected to ground through the case of the alternator. The other end is connected to the regulator. This system uses originally used a mechanical regulator (new replacements are quite often solid state) that switched power on and off to the field. In this system for the alternator to be the cause of the overcharging condition there would need to be an internal short between the field terminal and the alternator output terminal. This is not likely and if it were occurring the battery would run down when the engine is off.
In the 69+ system one end of the field is connected to switched battery voltage, that is if the key is in the run position there is voltage at the terminal on the alternator. The other end of the field is connected to the regulator. In this system the regulator controls the current through the field by switching the second connection to ground. In this system for the alternator to be the cause of the failure the second field connection would need to be shorting to the case. This would have a higher likely hood of occurrence but would most likely be always over charging or alternating between over charge and no charge.
The regulator decides when to turn the alternator on and off by sensing the voltage that powers the regulator. If this voltage is low it turns the alternator on and if it is high it turns it off. The power to the regulator comes from the battery through the bulkhead, to the fuse panel through the ignition switch and back out through the bulkhead connector before connecting to the regulator. Any bad connection along that path can result in a lower than battery voltage at the regulator. This will cause the regulator to turn the alternator on.
My first step would be to clean all the contacts in the bulkhead connector, clean the contacts with the fuses in the fuse panel and clean the contacts on the ignition switch. I would also check all my grounds. The regulator is grounded through the mounting screws. Make sure you have cleaned the paint off around the regulator around the mounting screws and use some toothed lock washers between the mounting tabs and the car to ensure a good connection. If you don't have a seperate ground strap between the block and the firewall add one, you could use one of the regulator mounting screws for one end of the ground strap.
If none of this helps you are going to have to start jumping wires to try an locate the problem.
Good Luck!
Dave
Quote:
Originally Posted by cecil4speed
[13.75 volts is on the low side of the acceptable range (you want 13.8 to 14.1 any time the engine is running) and 14.5 is a little to high but not outrageously high. 17 volts indicates that the regulator is not seeing the actual battery voltage. I would check the power feed to the regulator the difference between it and across the battery should be less than .5 volts. Dirty corroded connections between the battery and the regulator would be the culprit.]
I hope you don't mind th PM dgc333, but the old girl started charging really hard again today. Hard enough that I saw smoke coming from dash so I quick shut her down and unhooked the alternator and brought here home on battery power. Do you think that the alternator could be the culprit ?? I have checked and all connections seem to be clean. Thanks and any insight would be appreciated.
Dave I want to thank you very much. This is a great description on how the charging system works. I think I 've found my problem, bad regulator. I had already replaced this with a new one and it made no difference so I put the old one back on. This time when I took it off it had melted some of the sealant off on the back and you could look through the sealant and see where the printed circuit had rusted and lifted in some places. If you know how to post this it may help some one else. Thank you very much. I appreciate it. Hopefully I have it fixed, but I thought that once before. LOL
__________________
Dave Clement
68 Barracuda Sport Coupe
http://mysite.verizon.net/david.clement/
A failure of the alternator that would result in an over charge would be a very rare occurance.
The output of the alternator is controlled by turning current on and off to the field windings. I don't recall which system you have, pre 69 where there is just one wire connected to the field windings or the 69 up with two wires. This is in addition to the output terminal.
In the pre 69 system one end of the field windings is connected to ground through the case of the alternator. The other end is connected to the regulator. This system uses originally used a mechanical regulator (new replacements are quite often solid state) that switched power on and off to the field. In this system for the alternator to be the cause of the overcharging condition there would need to be an internal short between the field terminal and the alternator output terminal. This is not likely and if it were occurring the battery would run down when the engine is off.
In the 69+ system one end of the field is connected to switched battery voltage, that is if the key is in the run position there is voltage at the terminal on the alternator. The other end of the field is connected to the regulator. In this system the regulator controls the current through the field by switching the second connection to ground. In this system for the alternator to be the cause of the failure the second field connection would need to be shorting to the case. This would have a higher likely hood of occurrence but would most likely be always over charging or alternating between over charge and no charge.
The regulator decides when to turn the alternator on and off by sensing the voltage that powers the regulator. If this voltage is low it turns the alternator on and if it is high it turns it off. The power to the regulator comes from the battery through the bulkhead, to the fuse panel through the ignition switch and back out through the bulkhead connector before connecting to the regulator. Any bad connection along that path can result in a lower than battery voltage at the regulator. This will cause the regulator to turn the alternator on.
My first step would be to clean all the contacts in the bulkhead connector, clean the contacts with the fuses in the fuse panel and clean the contacts on the ignition switch. I would also check all my grounds. The regulator is grounded through the mounting screws. Make sure you have cleaned the paint off around the regulator around the mounting screws and use some toothed lock washers between the mounting tabs and the car to ensure a good connection. If you don't have a seperate ground strap between the block and the firewall add one, you could use one of the regulator mounting screws for one end of the ground strap.
If none of this helps you are going to have to start jumping wires to try an locate the problem.
Good Luck!
Dave
Quote:
Originally Posted by cecil4speed
[13.75 volts is on the low side of the acceptable range (you want 13.8 to 14.1 any time the engine is running) and 14.5 is a little to high but not outrageously high. 17 volts indicates that the regulator is not seeing the actual battery voltage. I would check the power feed to the regulator the difference between it and across the battery should be less than .5 volts. Dirty corroded connections between the battery and the regulator would be the culprit.]
I hope you don't mind th PM dgc333, but the old girl started charging really hard again today. Hard enough that I saw smoke coming from dash so I quick shut her down and unhooked the alternator and brought here home on battery power. Do you think that the alternator could be the culprit ?? I have checked and all connections seem to be clean. Thanks and any insight would be appreciated.
Dave I want to thank you very much. This is a great description on how the charging system works. I think I 've found my problem, bad regulator. I had already replaced this with a new one and it made no difference so I put the old one back on. This time when I took it off it had melted some of the sealant off on the back and you could look through the sealant and see where the printed circuit had rusted and lifted in some places. If you know how to post this it may help some one else. Thank you very much. I appreciate it. Hopefully I have it fixed, but I thought that once before. LOL
__________________
Dave Clement
68 Barracuda Sport Coupe
http://mysite.verizon.net/david.clement/
