Another oil-pressure-light/generator-light thread

Could Cycle Electric 12V generator wiring be the culprit?

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FlatheadMaverick
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Another oil-pressure-light/generator-light thread

#1

Post by FlatheadMaverick »

Like many others who've posted, my oil pressure light and generator light won't go out with the engine running, revving, etc. I've read every thread on this forum related to "why is my oil pressure light/generator light staying on." But none of them seem to take into account the slightly different wiring gymnastics that the 12V upgrade introduces, related to the Bosch regulator terminals. Am I overthinking things, like usual?

I remember when Dad and I wired this up several years ago, we got conflicting information from different users on what should be connected where on the regulator. All I know is, we settled on a method and the bike runs great... but both dummy lights refuse to go out.

I do have all the manuals, and also know where the diagrams are linked on this great site.

As for troubleshooting the oil pressure light, I disconnected the wire from the oil pressure switch (with the ignition on but the bike not running) and the light stays on. That means it's grounding somewhere in the dash, right? I'm a little overwhelmed with the electrical part of this, because there are four wires connected to the terminal above the lamp in the dash, and all diagrams say that's right for a '46 WL.

I want to ride this beautiful thing since we got it restored, but every issue I run into seems like you've got to remove three things to get access to the one area you need. Frustrating! I guess I'm learning patience this way.
old man emu
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Re: Another oil-pressure-light/generator-light thread

#2

Post by old man emu »

First, here's the wiring diagram:
46 WL wiring diagram.png
46 WL wiring diagram.png (200.86 KiB) Viewed 990 times
Let's look at the generator warning light.

This light works a bit like balance scale. When you turn on the ignition, current flows from Terminal 8 through the wire that runs under the instrument plate to the forward light terminal. The current goes to ground through the lamp and lights it. When the engine is running, current also comes up to Terminal 6 from the generator and tries to go to ground through the lamp. However, there is an equal voltage on the other side of the lamp since current is still available from Terminal 8. Since there is no voltage difference on either side of the lamp, not current flows and the lamp does not light up.

So, the first thing you must do is ensure that there is connectivity between Terminal 8 and the lamp. You should also check that there is current at Terminal 8. Just turn the ignition on and press the horn button. If it honks, you're OK. Then start the engine and see if there is current coming from the regulator to Terminal 6.

Since the oil warning light comes on when the oil pressure switch is disconnected, then both problems point to problems at Terminal 8 or with the oil warning lamp socket. If there is a short there, then that will give the generator light and the oil light a path to ground.

Can't help you with the Bosch regulator. I converted to a solid state one for my 12V system.
Mark44
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Re: Another oil-pressure-light/generator-light thread

#3

Post by Mark44 »

FlatheadMaverick wrote: Wed Oct 27, 2021 10:23 pm As for troubleshooting the oil pressure light, I disconnected the wire from the oil pressure switch (with the ignition on but the bike not running) and the light stays on. That means it's grounding somewhere in the dash, right? I'm a little overwhelmed with the electrical part of this, because there are four wires connected to the terminal above the lamp in the dash, and all diagrams say that's right for a '46 WL.
If the light stays on with the oil press. switch disconnected, the light has to be grounding somewhere else, like in the dash. I'm in the process of putting together a big twin flathead, and came across the same conundrum. At first I had an ordinary one-wire indicator light that grounds through its holder, not realizing that the ground path for the light has to be through the switch. After I changed the light to a two-wire insulated fixture, the light comes on when I turn on the ignition. I haven't gotten the beast running yet to find out if it also goes out when the engine is running.
old man emu wrote:This light works a bit like balance scale. When you turn on the ignition, current flows from Terminal 8 through the wire that runs under the instrument plate to the forward light terminal. The current goes to ground through the lamp and lights it. When the engine is running, current also comes up to Terminal 6 from the generator and tries to go to ground through the lamp. However, there is an equal voltage on the other side of the lamp since current is still available from Terminal 8. Since there is no voltage difference on either side of the lamp, not current flows and the lamp does not light up.
This seems like a reasonable theory, but I'm not sure it's right. More knowledgeable members will surely correct me if I'm wrong. I don't believe the voltages from the generator and the battery will be equal until such time as the generator brings the battery up to the voltage level that the generator is putting out. Perhaps the key is that the difference in voltages (likely < 1 volt) isn't enough to cause the light to illuminate.

As with my oil pressure light, I discovered you need a light that doesn't ground through its socket. My scenario is a bit different, as I'm running a Cyclelectric gennie with built-in regulator. One lead of the voltage light goes to the "L" terminal on the regulator, and the other lead goes to battery positive.
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Re: Another oil-pressure-light/generator-light thread

#4

Post by Andygears »

2 lights, both get power, 12v+, at all times when the key is on, to one terminal.

The other terminal: oil pressure light is normally grounded and open, light off, when engine has oil pressure.

Generator light is normally grounded but changes to positive once generator spins and makes 12v+. Positive on both terminals shuts light off.

Neither socket can be grounded.

Andygears
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Re: Another oil-pressure-light/generator-light thread

#5

Post by Frankenstein »

Is it a magneto equipped bike perchance?
As per the genny light, the battery VOLTAGE nearly always be equal to the generator output voltage, except for wire losses. If the battery is very discharged, it will pull down the genny output somewhat. Not knowing what the "L" terminal on the CE regulator is connected to, I can only surmise that it acts like the armature connection and gives a ground to the light when not running. as it spins up, it generates VOLTAGE and leads to the scenario Emu describes.
As for both lamps lighting, perhaps faults in their lines at the dash or some common wiring route? The oil sending unit at least almost has to have a ground to it somewhere. IF they never worked, suspect incorrect lamp sockets!
DD
FlatheadMaverick
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Re: Another oil-pressure-light/generator-light thread

#6

Post by FlatheadMaverick »

Thanks, all, for your detailed posts. I ended up having cataract surgery in both eyes since I posted -- can't believe how bad my vision was now that it's fixed -- and I'm still in the "don't do this or that" stage. Looking forward to digging back into this, now that it's getting colder in my neck of the woods.
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