Generator Warning Light

[CA Victoria]

Ive been looking into wiring a generator warning light.
As I understand the bulb is wired in between the Arm side of the Gen and the Bat side of the ignition switch ( or regulator).
The bulb is lit when Gen is not charging and the voltage difference is detected.
Is a special bulb needed since the bulb is not wired to a ground?

Thank you in advance.

[ford38v8]

Now I've heard everything!
One of the desirable features of having an antique car is that antique cars have actual dials and gauges instead of idiot lights.

[koates]

Generator warning lights were almost a standard fitting on British and some European and American cars. The two terminals of the bulb were connected between the switched side of the ignition switch and the generator or armature terminal on the voltage regulator. The bulb is only about 2 or 3 watts. It was sometimes called the ignition warning light. Quite common really on 1940s, 50s, and 60s cars. Light comes ON when ignition is turned ON and goes OFF when engine is started and generator starts charging with a few revs up. Regards, Kevin..

[cadillac512]

Originally Posted by CA Victoria

Ive been looking into wiring a generator warning light.
As I understand the bulb is wired in between the Arm side of the Gen and the Bat side of the ignition switch ( or regulator).
The bulb is lit when Gen is not charging and the voltage difference is detected.
Is a special bulb needed since the bulb is not wired to a ground?

Thank you in advance.

Hi Tim. The bulb is not really special (other than being very low wattage as koates said) but has to be isolated from ground. Care should be taken to insulate the mounting of the socket so the brass base of the bulb isn't grounded in the normal manner. OR a more modern bulb and socket can be used (like a #194 dash bulb) with its ungrounded type socket.

[CA Victoria]

Thank you fellas.
I have a Stewart Warner lamp base with both contacts that are isolated, will give it a whirl today.

[CA Victoria]

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Today: I built my own wire harness with provisions to pull in additional wires as the build progresses, I added another wire for the light & it worked perfectly.
Once I tidy up a few things I will post some photos......there are a few in my album: Too-Mater.

[cadillac512]

Great!

[Stretch Cab]

Is this the light you were talking about?

[Mart]

Not sure if mentioned but the feed goes from the ign side of the ign switch not the bat side. It passes through the bulb, (low wattage) to the arm terminal on the regulator.

It works like this.
Turn ign on, bulb gets 12v, and finds ground through the heavy windings of the armature.
Engine starts, revs come up, armature voltage comes up and the cutout closes. Bulb effectively gets 12v from both sides so goes out.
For 12v substitute 6v if relevant.

I would disagree with the idiot light comment, it can be useful in highlighting if you have left the ignition on by accident.

I have a light on some cars but not all.

Mart.

[rotorwrench]

If a person has a 10si alternator conversion instead of a generator, the two terminals that aren't used for single wire operation could be used for their intended purpose. One of which is voltage sense and the other for the GEN warning light.

If a person has a 3-brush generator then an old Delco Remy cut out has a terminal for a warning light. My old Harley 45 is set up that way.

[JayChicago]

I would think an idiot light sensing no oil pressure is more important. That too would be useful in highlighting if you have left the ignition on by accident.

[tubman]

Originally Posted by JayChicago

I would think an idiot light sensing no oil pressure is more important. That too would be useful in highlighting if you have left the ignition on by accident.

I had a great big red one on the hemi in my dirt car! It was mounted right next to the tach.

[5851a]

I like gauges, but after a long long trip of constantly monitoring gauges a red light gets your attention.