Exciter Voltage Stays On
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From: Clearwater FL
Exciter Voltage Stays On
Have an issue with the exciter wire staying on when the key is in the off position. This cased my alternator to fail and cooked the connection for the exciter wire at the alternator. Put on a fresh connector for the R and F wires with a new alternator. Hooked it up and it started to smoke a little after 5 min and made the connector and alternator hot. Tested with a multi-meter and no matter the key position there is full 12.5 volts going through the exciter wire. The only way to cut the juice on the exciter wire is to disconnect the battery. Any ideas on a fix?
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From: Clearwater FL
Any thought on how to check it as the switch went to the front of my list but I'm not too informed on exciter wires and the circuits that make it work. Is the wire to stay on with voltage going to it after the engine has started or is the exciter wire only to stay with 12 volts at start up and then turn off once the alternator starts generating?
Le Mans Master
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From: McHenry Illinois
Your alternator should have 3 wires, the bat wire , and 2 on the plug, one of which is hot to battery and the other which is ign powered. So with key on, you should have power to all 3, key off power to 2 of them. The brown (exiter wire) should be powered only with key on.
PM your e-mail address if you want me to send you a schematic.
PM your e-mail address if you want me to send you a schematic.
Last edited by '75; May 30, 2015 at 06:11 PM.
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From: South Western Ontario
And the switched 12V should be a brown wire on terminal 1 while the constant 12V should be a red wire on terminal 2. It sounds like your car is wired backwards.
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Joined: Dec 2010
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From: Clearwater FL
Your alternator should have 3 wires, the bat wire , and 2 on the plug, one of which is hot to battery and the other which is ign powered. So with key on, you should have power to all 3, key off power to 2 of them. The brown (exiter wire) should be powered only with key on.
PM your e-mail address if you want me to send you a schematic.
PM your e-mail address if you want me to send you a schematic.
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From: Clearwater FL
So your telling me the #2 wire is hot all the time? That's not the case as it is hot only in the run position. I know they are not switched from the repair as I was extremely diligent in doing one wire at a time and not mixing them. Yes, #1 wire is dark brown in color.
Le Mans Master
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From: McHenry Illinois
If the wires were crossed, it would cause the alternator to back feed the ignition system and stay running after the key is off. (provided the alternator is working) I've seen this happen when the connector was changed. Won't hurt to try swapping them to be sure, as a test.
Race Director
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From: South Western Ontario
So your telling me the #2 wire is hot all the time? That's not the case as it is hot only in the run position. I know they are not switched from the repair as I was extremely diligent in doing one wire at a time and not mixing them. Yes, #1 wire is dark brown in color.
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From: Clearwater FL
So you believe no harm to the system by swapping the wires for a test? If that is the case with the #2 staying hot all the time you would think at the least it would drain the battery in a short period of time.
Race Director
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From: South Western Ontario
With the #1 terminal connected directly to power you're using that power source to feed full-voltage to the field coil and that will draw a lot of current on that terminal as well as drain the battery rather quickly. When normally connected, this terminal is ignition switched and also has a resistor or light in series to limit the current.
Terminal #2 has a high input impedance and you can continually apply power to it without causing a battery drain.
Terminal #2 has a high input impedance and you can continually apply power to it without causing a battery drain.
Le Mans Master
Joined: Dec 2007
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From: McHenry Illinois
With the #1 terminal connected directly to power you're using that power source to feed full-voltage to the field coil and that will draw a lot of current on that terminal as well as drain the battery rather quickly. When normally connected, this terminal is ignition switched and also has a resistor or light in series to limit the current.
Terminal #2 has a high input impedance and you can continually apply power to it without causing a battery drain.
Terminal #2 has a high input impedance and you can continually apply power to it without causing a battery drain.
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From: Clearwater FL
Thanks for the suggestion. I see all the different ways the diagrams have it laid out and the #2 looks like it's hot all the time. I never wanted to know this much about exciter wires but I'm learning for sure.