Charge System Ex[plained - May help someone else.

[cecil4speed]

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/

 

[cecil4speed]

Originally Posted by cecil4speed
Quote:
Originally Posted by cudaman51
Yes sorry but I still have the problem. I have 3 wires on my alternator. I do have battery voltage on the battery terminal,the connection with 10 of 12 gauge wire which is held on by the nut. I unhooked the brown field wire which is next to the battery terminal connection and the car wouldn't charge at all, hooked it back up and it still charged over 17.5v. The 3rd field wire is yellow. I didn't check that in any way. Maybe alternator ?? I thought of running 2 new wires to the regulator, but I don't have a wiring diagram. Do these 2 wires to the regulator go to anything else or directly to the regulator ? And where does the 3rd yellow field wire go ? Can I check it some how ? Thanks.

Quote:
Originally Posted by cecil4speed
Quote:
Originally Posted by cudaman51
Quote:
Originally Posted by cecil4speed
Hope you don't mind the private message but you gave me good advise when the Dart was over charging. Well it started again today, Went up to over 17v.You told me to check the dark green wire on yhe field terminal to see if it went to ground. I don't have a dark green wire but I have a brown wire going to the field terminal next to the battery terminal. The other field wire is yellow. I checked and the brown wire does have some resistance but I think it does go to ground. I'm not familar with the 3-wire alternator setup. I'm used to the 2-wire setup with point style regulator. I don't really know how to trace this setup. Do you know where I can get a wiring diagram ? You see this is a 68 but some one before me changed this over and it is setup with chrome box electronic ignition, so probably they needed to change over for this. Funny thing is I drove the car last September & October with no problems at all, so over winter something happened. I think maybe alternator ?? Any help would be appreciated. Thanks, Keith.

no problem at all. of the two wires on the altornator one is battery power infrom the ignition switch witch is the same wire *** the one on the ballast resistor and regulator the outher wire suplies the ground path through the voltage regulator .thats what turns the altornator on. if you lift it it should stop chargeing .that wire goes to the regulator. of the two wires on the regulator the outher one must be the same as the battery voltage. it should alsow stop chargeing whe you unplug the regulator. if you still have trouble pm me again.

Yes sorry but I still have the problem. I have 3 wires on my alternator. I do have battery voltage on the battery terminal,the connection with 10 of 12 gauge wire which is held on by the nut. I unhooked the brown field wire which is next to the battery terminal connection and the car wouldn't charge at all, hooked it back up and it still charged over 17.5v. The 3rd field wire is yellow. I didn't check that in any way. Maybe alternator ?? I thought of running 2 new wires to the regulator, but I don't have a wiring diagram. Do these 2 wires to the regulator go to anything else or directly to the regulator ? And where does the 3rd yellow field wire go ? Can I check it some how ? Thanks.

First we must verify the wires. unplug both field wires at the altornator and then unplug the voltage regulator.turn the key on to the run position check the voltage 0n both ends and take note you should have 12 volts on only one wire on each end. that should be comen to the ignition wire and the same voltage as the battery.if you have, that is the power in for both devices.the remaining wire simply runs from the regulator to the aternator you should have continuity from end to end and infinite from one end to ground.if all those conditions are true your wireing is ok.to check the alternator hook the regulator back up and plug the hot wire back in on the alternator. start the car it should not charge. If it does the field is grounded internaly(bad alternator).If the alternator passes the test and it still over charges when its hooked back up its the regulator.I hope this works for you. let me know.

That is great cudaman. I will check tonight. Just to make sure. I unplug the 2 field wires, also disconnect the hot battery wire connected to the alternator. Unplug the regulator, turn key on to ignition, one wire will have 12v on each end. If it does I check the second field wire. Check second wire for continuity and check each end to ground and this should be infinate. If this is ok leave both field wires unpluged. Now hook the hot battery connection back up, with both field wires unhooked, and hook regulator up. Start her up and it should not charge, but if it does charge it is a bad alternator. If no charging, hook both field wires up and if it over charges now it is the regulator that is bad. Please let me know if I have it straight. Thanks again.[/quote]whell allmost. leave the large hot lead on the alternator. i meant for you to distinguise witch of the two field wires is hot.thats the hot lead i was refering two.