One-wire alternator installed, ALT light stays on

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   I just installed a Tuff Stuff 140-amp alternator because I'm going to upgrade to electric fans and relays to run the headlights from the battery. I unplugged the wires from the voltage regulator and from the old alternator and tucked them away. The new alternator charges -- I have a bit over 14.5 volts at idle once the car is warmed up -- but the ALT light stays on. Any ideas?

The belt is slightly loose because the pulley on the new alternator is ever so slightly smaller than on the old one, and it's adjusted as far out on the bracket as it will go. I know I need to find a belt 1/2" to 1" shorter. Will that make a difference with my light? I wouldn't think to look there because I have 14.5V, so it does seem to be charging.

Also, there are two fusible links that are hooked to the battery side of the starter solenoid, neither of which I know what they're for. Do I need to disconnect one or both?

I did run a ground wire from the new alternator's grounding tab to the block, and upgraded to a 4-gauge charging wire.

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Inkara1 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 17-November-2021 Location: Ridgecrest, CA Status: Offline Points: 284	Post Options Post Reply Quote Inkara1 Report Post Thanks(0) Quote Reply Topic: One-wire alternator installed, ALT light stays on Posted: 19-November-2022 at 2:21PM
	I just installed a Tuff Stuff 140-amp alternator because I'm going to upgrade to electric fans and relays to run the headlights from the battery. I unplugged the wires from the voltage regulator and from the old alternator and tucked them away. The new alternator charges -- I have a bit over 14.5 volts at idle once the car is warmed up -- but the ALT light stays on. Any ideas? The belt is slightly loose because the pulley on the new alternator is ever so slightly smaller than on the old one, and it's adjusted as far out on the bracket as it will go. I know I need to find a belt 1/2" to 1" shorter. Will that make a difference with my light? I wouldn't think to look there because I have 14.5V, so it does seem to be charging. Also, there are two fusible links that are hooked to the battery side of the starter solenoid, neither of which I know what they're for. Do I need to disconnect one or both? I did run a ground wire from the new alternator's grounding tab to the block, and upgraded to a 4-gauge charging wire.
	1972 Gran Torino station wagon, light blue, 351C 2V, prior owner upgraded to 4V (2V heads), originally had a C4 but prior owner changed to C6 for some reason.

californiajohnny Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Joined: 05-October-2013 Location: winlock, wa Status: Offline Points: 14609	Post Options Post Reply Quote californiajohnny Report Post Thanks(0) Quote Reply Posted: 19-November-2022 at 11:26PM
	voltage needs to flow through the light to turn it off, since you're not running the energize wire it wont turn off, can't remember what i heard to trick the light...you may be able to remove it??? the fusable links are usually for accessories in the car like main power supply to dash lights, radio, etc.... someone else may know more on the 1 wire deal...
	JOHN 74 GRAN TORINO S&H CLONE 74 VETTE CUSTOM 90 S10 BLAZER 4X4 LIFTED 77 CELICA CUSTOM 75 V8 MONZA SUPERCHARGED 79 COURIER VERT. SLAMMED 75 VEGA V6 5 SPD 70 CHEV C10 P/U 68 MUSTANG FB CONVERSION

Greg73Oregon Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 23-February-2021 Location: Roseville, CA Status: Offline Points: 232	Post Options Post Reply Quote Greg73Oregon Report Post Thanks(0) Quote Reply Posted: 20-November-2022 at 4:07PM
	Perhaps your new alternator has a terminal similar to the Jeg's or Delco (???): NO WARNING LIGHT Note that a 1-wire alternator does NOT permit the use of a charge warning (idiot) light. Most hot rodders and muscle car enthusiasts prefer the use of a voltmeter or ammeter to monitor charging. However, certain JEGS alternators have terminals that may be used for a warning light. To wire a warning light using one of these alternators, simply remove the terminal plug cover and connect the R (Left terminal, looking from the back of the alternator) to the warning light wire. Edited by Greg73Oregon - 21-November-2022 at 6:51AM
	GKF

72FordGTS Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group GTS.org Admin Joined: 06-September-2005 Location: Ontario, Canada Status: Offline Points: 5854	Post Options Post Reply Quote 72FordGTS Report Post Thanks(0) Quote Reply Posted: 21-November-2022 at 8:26AM
	I agree with the others. The one wire alternators don't generally work with the charge light. You could bypass the light and install a voltmeter. However, if you want to keep the charge light, there are alternative to the one wire that you can install. There are some high amperage Ford 1G alternators, or you could also convert to a Ford 3G.
	Vince 1972 Ford GTS Sportsroof - Survivor, One Family car GTS.org Admin

Inkara1 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 17-November-2021 Location: Ridgecrest, CA Status: Offline Points: 284	Post Options Post Reply Quote Inkara1 Report Post Thanks(0) Quote Reply Posted: 21-November-2022 at 11:04AM
	I want the light to go off, not stay on. If I just pull the light bulb, will that mess anything up? The electric choke power wire is tapped off a light green wire with a red stripe near the starter solenoid. Since I unplugged everything from the voltage regulator, if I pull the bulb, will I still have power to the choke?
	1972 Gran Torino station wagon, light blue, 351C 2V, prior owner upgraded to 4V (2V heads), originally had a C4 but prior owner changed to C6 for some reason.

Inkara1 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 17-November-2021 Location: Ridgecrest, CA Status: Offline Points: 284	Post Options Post Reply Quote Inkara1 Report Post Thanks(0) Quote Reply Posted: 08-March-2023 at 7:46AM
	Many months later... I finally did a bit more digging on this. I had unplugged the wires from the voltage regulator, but the electric choke was tapped off the green/red stripe wire. So if I drive the car for a while, the light gets very dim but not fully off. Today, I unplugged the electric choke and the ALT light went off. I plugged the choke back in and the light came back on. Now the question is if there's another wire that's on with the key in "run" but off with the ignition off besides the green/red stripe wire.
	1972 Gran Torino station wagon, light blue, 351C 2V, prior owner upgraded to 4V (2V heads), originally had a C4 but prior owner changed to C6 for some reason.

72 RS 351 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 04-September-2014 Location: Knoxville TN Status: Offline Points: 2767	Post Options Post Reply Quote 72 RS 351 Report Post Thanks(0) Quote Reply Posted: 08-March-2023 at 9:00AM
	It's been common to have an alternator wire connected through a circuit including a dash light etc. It may be time to add a diode to a wire somewhere to isolate part of a circuit.
	*Don* 73 Ranchero "Sport 72 front end", floor shift/console, planning EFI 7000+ rpm 351-4V &4R70W 73 Ranchero GT 351C-4V &4R70W for sale later. 92 Lincoln Mark VII SE GTC, OBDII 347/4R70W

Greg73Oregon Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 23-February-2021 Location: Roseville, CA Status: Offline Points: 232	Post Options Post Reply Quote Greg73Oregon Report Post Thanks(0) Quote Reply Posted: 08-March-2023 at 9:58AM
	American Autowire makes a circuit that uses the existing "Idiot Light" for 1-wire alternator installations. Kit comes with everything you need: https://www.americanautowire.com Note: The dash "Idiot Light" is normally connected to a 3-wire alternator's excitor wires. Unlike a generator with permanent magnets, an alternator uses electromagnets.
	GKF

Inkara1 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 17-November-2021 Location: Ridgecrest, CA Status: Offline Points: 284	Post Options Post Reply Quote Inkara1 Report Post Thanks(0) Quote Reply Posted: 09-March-2023 at 7:48AM
	Update: the Tuff Stuff alternator has a rubber plug with two spade connectors underneath. The instructions state that the one on the left as you face the rear of the alternator is to hook to an alternator light. So I hooked the choke wire to it and the choke opens, but because my green/red stripe wire is unhooked, the alt light is off as I hoped for. I plan to use a voltmeter. If anything, the choke opens too fast now, even though I thought Holley chokes needed the full 12V. I guess I can try turning the choke cap or finding a resistor to splice into the choke power wire.
	1972 Gran Torino station wagon, light blue, 351C 2V, prior owner upgraded to 4V (2V heads), originally had a C4 but prior owner changed to C6 for some reason.

Inkara1 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 17-November-2021 Location: Ridgecrest, CA Status: Offline Points: 284	Post Options Post Reply Quote Inkara1 Report Post Thanks(0) Quote Reply Posted: 01-July-2023 at 8:48PM
	Another update: the Tuff Stuff alternator took a crap on me tonight. I started the engine and the belt was squealing. That went away, but I was only at ~12V instead of the 14.5V I would normally be at. Plus, the pulley is severely discolored from heat. So it lasted me from early November until July 1. It has a 1-year warranty, but only if sent on my dime in the original box, because of course everyone keeps the empty box sitting around for a year. So I guess I'm switching to 3G if for no other reason than if I lose an alternator again, but this time out of town, I have hope of being able to find one at a parts store. But hey, I guess that means I can hook the green/red wire again and have my ALT light back.
	1972 Gran Torino station wagon, light blue, 351C 2V, prior owner upgraded to 4V (2V heads), originally had a C4 but prior owner changed to C6 for some reason.

Inkara1 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 17-November-2021 Location: Ridgecrest, CA Status: Offline Points: 284	Post Options Post Reply Quote Inkara1 Report Post Thanks(0) Quote Reply Posted: 08-July-2023 at 10:19AM
	The 3G is in. Now I have my ALT light again... in fact, it doesn't turn off. Any ideas why? It is charging, according to the volt meter I have plugged into the lighter socket (~14.2 running, mid-12s when engine is off, so I believe the meter is reading correctly). I did run the choke off the green/red stripe wire this time, but I kind of doubt that's the issue because I had the choke on that wire with the 1G and didn't have an everlasting ALT light. If it IS the choke causing it, is there another good power source that's on with the key? Maybe the wiper motor, but which wire should I tap from?
	1972 Gran Torino station wagon, light blue, 351C 2V, prior owner upgraded to 4V (2V heads), originally had a C4 but prior owner changed to C6 for some reason.

bdaugette Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 02-December-2013 Location: United States Status: Offline Points: 259	Post Options Post Reply Quote bdaugette Report Post Thanks(0) Quote Reply Posted: 08-July-2023 at 12:41PM
	I was thinking there is a voltage regulator adapter that you can use: https://www.paperformance.com/3g-adapter-462802b/
	Bill Daugette 72 GTS 351C 4V

Inkara1 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 17-November-2021 Location: Ridgecrest, CA Status: Offline Points: 284	Post Options Post Reply Quote Inkara1 Report Post Thanks(0) Quote Reply Posted: 08-July-2023 at 2:25PM
	I'd bought a Painless wire harness, though it doesn't have a resistor on the green/red stripe wire like the one in the link. But the picture in the link has the instructions in the background, and that says to splice the choke into the white/black wire. Maybe I can try that tonight with my current harness and see if it makes a difference.
	1972 Gran Torino station wagon, light blue, 351C 2V, prior owner upgraded to 4V (2V heads), originally had a C4 but prior owner changed to C6 for some reason.

bdaugette Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 02-December-2013 Location: United States Status: Offline Points: 259	Post Options Post Reply Quote bdaugette Report Post Thanks(0) Quote Reply Posted: 08-July-2023 at 3:08PM
	That would be nice if it works. I have the 3G alternator in a box to install in the fall.
	Bill Daugette 72 GTS 351C 4V

Inkara1 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 17-November-2021 Location: Ridgecrest, CA Status: Offline Points: 284	Post Options Post Reply Quote Inkara1 Report Post Thanks(0) Quote Reply Posted: 08-July-2023 at 6:26PM
	Good news! I relocated the choke to the white/black stripe wire, so nothing is tapped off the green/red stripe wire anymore, and now the ALT light goes off.
	1972 Gran Torino station wagon, light blue, 351C 2V, prior owner upgraded to 4V (2V heads), originally had a C4 but prior owner changed to C6 for some reason.