Someone please explain 'Reverse Current To Open'

[Stephenorf]

Can someone conceptually explain the generator regulator spec that states "Reverse Current To Open-Amps".

The reason I ask is this: I converted to Pertronix with a relay, everything works fine. Except (there's always an 'except') when I turn the key to the 'off' position the car keeps running. This is being caused by power back-feed through the Armature terminal going to the GEN light in the dash. My question is regarding the "Reverse Current" spec. Is the generator regulator working properly.

Someone suggested "Generator regulators contain a solenoid to disconnect the generator from power and the switch, which prevents back-feed." Looking for feedback on the spec before I buy a new generator, or install a diode.

[40cpe]

"IF" your engine was shutting off properly before the Pertronix/relay install, I would revisit the relay wiring. Ignitions draw a relatively small amount of power and the ignition switch should handle it with no problem. Sorry I can't answer your original question.

[Stephenorf]

Originally Posted by 40cpe

"IF" your engine was shutting off properly before the Pertronix/relay install, I would revisit the relay wiring. Ignitions draw a relatively small amount of power and the ignition switch should handle it with no problem. Sorry I can't answer your original question.

Thanks, I don't think the ignition switch is having any problem handling the power, its just when I turn the key to off position the car keeps running. I've isolated the issue to the GEN light wire that hooks up to the "A" terminal on the generator Regulator (voltage regulator). When I disconnect the GEN light wire at the VR, the car shuts off like it should (via turning the ignition switch to the OFF position). That's why I'm wondering about power back-feed.

Also, when I turn the key to the OFF position the GEN light in the dash turns on.

Unfortunately I canot say for sure if it was working properly prior to the relay. The car was DOA when I got it and one of the first things I did was ditch the points and install the pertronix setup. I'm pretty sure I had it running prior to the pertronix conversion and it would shut off with the key.

[GLAmes]

I'd try a diode first. They are an easy install and don't cost much.

[KULTULZ]

Originally Posted by Stephenorf

Can someone conceptually explain the generator regulator spec that states "Reverse Current To Open-Amps".

The reason I ask is this: I converted to Pertronix with a relay, everything works fine. Except (there's always an 'except') when I turn the key to the 'off' position the car keeps running. This is being caused by power back-feed through the Armature terminal going to the GEN light in the dash. My question is regarding the "Reverse Current" spec. Is the generator regulator working properly.

Someone suggested "Generator regulators contain a solenoid to disconnect the generator from power and the switch, which prevents back-feed." Looking for feedback on the spec before I buy a new generator, or install a diode.

There is (was) a feature in a period correct mechanical VR called the 'REVERSE CURRENT CUT OUT'

Refer to the WSM to diagnose.

Now the PERTRONIX, it is directly attached to the BAT with an IGNITION SW triggered relay with no crossing with either the charging or IGN SYSTEMS?

Also check for sticking mechanical points. They may need to be filed. The VR is also adjustable. All connections and grounds good?

Is your VR OEM FORD or a service replacement?

[justold]

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someone correct me if I am wrong . the conductor going to the lamp should be connected to the field terminal on a ford product not the armature terminal.

[KULTULZ]

Here is a 12V GEN & VR SCHEMATIC -

[KULTULZ]

I don't think the ignition switch is having any problem handling the power, ...

Is the install an IGN I or II?

You really need to consider powering it off BAT VOLT via relay as the condition of an original 1957 wiring harness and switch may be questionable.

[Stephenorf]

OK, here's my setup: I have a Pertronix coil and ignitor in conjunction with the 312 and generator setup in my 1959 Mercury Monterey.

Generator Diagram: It's the "Small Yellow / Black" wire that excites the GEN bulb in the dash.

Gen & Regulator DIagram.jpg

I'm using a relay to power the coil/ignitor: The 'switch' wire is from the ignition and should only have power when the key is in the "On" position.

Screenshot 2025-05-30 203943.jpg

When I initially hooked all this up, the car started right up and idled well. But when I turned the key to the off position, the motor kept running. So I did more research.

Here's the instruction from Pertronics for early Ford/Chevy vehicles:

Screenshot 2025-05-30 204053.jpg

And here's the diagram from Pertronics showing the diode spliced inline with the "Small Yellow / Black" wire that excites the GEN bulb in the dash:

Screenshot 2025-05-30 110524.jpg

I tested the relay while the car was running with the key off: I disconnected the "run" wire (ignition-switched wire) that trips the relay. When I disconnected the wire, the relay closed and the car stopped.

Next I observed that the "GEN" light would illuminate when the car was running while the key was in the "off" position.

Finally, I disconnected the "Small Yellow / Black" from the generator regulator. Once that "Small Yellow / Black" was disconnected, I can use the ignition switch to start and run the engine, and it shuts down when I turn the switch to the off position.

Someone suggested the regulator might be faulty, and that adding the diode might fix the "engine running when the switch is in the off position, but that there may be an issue with the regulator that would cause the battery to drain when the car was "off".

Soo....I was just asking what the 'Reverse Current To Open' spec is on the generator regulator. After further internet sleuthing, it seems a generator can introduce reverse polarity charge to the system, and evidently the 'Reverse Current To Open' just states the minimum reverse polarity current (amperage) needed for the generator regulator to 'protect' the system from the reverse polarity.

I guess I will buy another regulator and see if the car runs on off, or if it shuts down properly. My assumption will be that the new regulator is not defective. If after installing the new regulator if the car continues to run while the key is in the off position, then it must just be some known circuit condition (some sort of 'power back-feed' scenario) on these older cars when the relay is used as described above.

Whew...don't kill me for being long winded....but this is where I am on the Pertronix ignition install.

[KULTULZ]

Do me a favor if you can, call these guys and explain your situation -

https://www.precision-pwr.com/voltag...-generator-cut

Mechanical to solid state conversions for voltage regulators and generator cutouts, maintaining 100% original appearance!

If you notice in the PERTRONIX memo, it (diode) refers to an ALT circuit.

They should be able to rebuild/upgrade your VR, especially if an original FORD. I would hate to think of the quality of anything new you can buy today.

Now the PERTRONIX, is it the IGN I or II? The actuating wire for the relay is running off the I terminal of the IGN SW?

ADDENDUM -

HERE - https://www.fordbarn.com/forum/showthread.php?t=307971

... is a like URL that will help explain a GEN MECH VR. I remember in the day (along with draining alcohol ... ... based coolant) changing VR points adjustment for summer warmer weather.

[rich b]

Originally Posted by Stephenorf

Next I observed that the "GEN" light would illuminate when the car was running while the key was in the "off" position.

Finally, I disconnected the "Small Yellow / Black" from the generator regulator. Once that "Small Yellow / Black" was disconnected, I can use the ignition switch to start and run the engine, and it shuts down when I turn the switch to the off position.

So, did you install a diode in the charge wire?

Since you proved it was the source of the feedback that prevented engine shut off.

[Stephenorf]

Originally Posted by rich b

So, did you install a diode in the charge wire?

Since you proved it was the source of the feedback that prevented engine shut off.

No, not yet. I will soon though. For now, the engine starts and stops as it should. I just diconnected the GEN lamp lead. I have the diode, I just need to design and fabricate a solution to adding the diode in-line without modifying the existing wiring. I guess temporatily I could use aligator clips to test the solution before creating something more long term/permanent. Hmmm...I'll let you know how it goes.

[rotorwrench]

A person would have to bypass the generator light to test the theory but it is a situation that can happen with the more sensitive electronic ignitions. In a normal points ignition, the power is fully cut to the coil when the key is off. The old regulators that have a cut out pole will do so as soon as the generator stops producing enough power to keep the generator system on line. When the cut out opens, it closes a switch to the generator light but the power comes from the ignition switch. An alternator is different in that it had a diode bridge to keep reverse current from getting back into the field or rotor. They only use a two pole regulator for voltage regulation and current limiting. This requires a different pathway for the gen/alt light function The generator has all three unless it's an old 3-brush type generator made prior to the 1939/40 time frame for cars and later for tractors.

A diode may be necessary for a generator or alternator light set up where the light comes on due to back flow from the regulator. The later alternators with the internal solid state regulator use a small multi-pin plug and a large power terminal known as a one wire to most folks but the multi pin plug is used to pre-excite the alternator through the generator light. The 11si GM alternator is a good example of this.

The OP's diagram indicates an original 3-pole. The power is being fed from the armature back into the system. It will need a diode to allow current to flow only one way during key on engine function but stop it from feeding back to the light with key off. The light only needs power and ground to work as long as the engine is not running with key on. A soon as it starts, the cut out closes and simultaniously opens the other points set in the regulator that control the generator light to turn it off. Generator on, light off. Generator off, light on as long as the key switch is on. In your case the power doesn't go off with the key turned off and when the light is on then the power gets through it to the ignition modual so the ignition won't cut off. Hopefully they recommend a diode to use and where to put it. It looks like it's controlling the ground side but it depend on which side the power comes from. The way it looks, it keeps power from comming back through the ground side.

[Stephenorf]

Update: I used alligator clips to temporarily add the diode inline between the regulator and the GEN lamp.

Here's the diode I purchased long ago in preparation for this mod.

Screenshot 2025-06-11 073355.jpg

I had already disconnected the GEN lamp wire at the regulator. Using alligator clips I wired the diode between the GEN lamp feed-wire and the "A" terminbal on the regulator.

Diode alligator clips annotated.jpg

drum roll....and the results are as expected! When I turn the key to the "off" position the engine turns off. And...when the enging is NOT running, turning the key to the "run" position causes the GEN lamp to illuminate.

GEN lamp illuminated.jpg

Now I just need to fabricate a little panel for the diode so I can permanently insert it in-line without modifying any of the factory wiring. I need to have a spade terminal at the regulator end, and a spade terminal block at the other end.

[Stephenorf]

Originally Posted by rotorwrench

A person would have to bypass the generator light to test the theory but it is a situation that can happen with the more sensitive electronic ignitions. In a normal points ignition, the power is fully cut to the coil when the key is off. The old regulators that have a cut out pole will do so as soon as the generator stops producing enough power to keep the generator system on line. When the cut out opens, it closes a switch to the generator light but the power comes from the ignition switch. An alternator is different in that it had a diode bridge to keep reverse current from getting back into the field or rotor. They only use a two pole regulator for voltage regulation and current limiting. This requires a different pathway for the gen/alt light function The generator has all three unless it's an old 3-brush type generator made prior to the 1939/40 time frame for cars and later for tractors.

A diode may be necessary for a generator or alternator light set up where the light comes on due to back flow from the regulator. The later alternators with the internal solid state regulator use a small multi-pin plug and a large power terminal known as a one wire to most folks but the multi pin plug is used to pre-excite the alternator through the generator light. The 11si GM alternator is a good example of this.

The OP's diagram indicates an original 3-pole. The power is being fed from the armature back into the system. It will need a diode to allow current to flow only one way during key on engine function but stop it from feeding back to the light with key off. The light only needs power and ground to work as long as the engine is not running with key on. A soon as it starts, the cut out closes and simultaniously opens the other points set in the regulator that control the generator light to turn it off. Generator on, light off. Generator off, light on as long as the key switch is on. In your case the power doesn't go off with the key turned off and when the light is on then the power gets through it to the ignition modual so the ignition won't cut off. Hopefully they recommend a diode to use and where to put it. It looks like it's controlling the ground side but it depend on which side the power comes from. The way it looks, it keeps power from comming back through the ground side.

Thank you. This is an excellent description of the issue I am facing once I added a relay for the Pertrronix ignition. I don't completely understad some of the finer details, but overall it makes sense and aligns to my understadning of the issue.

I added the diode with the black stripe end oriented toward the GEN lamp (away from the regulator) and it works as a fix to allow the engine to be shut off using the ignition switch.