Topic: single wire turn signals come on but don't flash

[gecko672]

Hey Phil, thanks for the info, just to be clear and so I understand which picture is being talked about,
I uploaded 4 photos:
picture 1 - turn signal
picture 2 - close up of the wires that come from the replacement switch ( you had asked for a photo) light blue, green, orange, grey
picture 3 - close up of the light blue 4 way junction that the right turn signal is plugged into.
picture 4 - the orange 4 way junction left turn signal is plugged into ( hard to see though)

I assume your talking about picture 3. That green you see in this his photo is not actually a ground, its the wire that leads to the turn signal. The turn signals only came with one wire and it happens to be green, just to make things confusing.

[gecko672]

I might just go through all the connections in the bucket and double check. Ive obviously got something wrong. At least I know where to look now and why the flasher wont work.

[Vinhead1957]

Right turn signal blue left turn orange

[raymond10078]

After reviewing the schematic, I recommend that you do this test:  disconnect the blue and orange wires from the speedometer (that light up the turn signal light), then try the turn signals to see if the two sides are now split.

I expect that if the rest of your wiring is correct, this should work.  The only thing I can't tell from the schematic is which of the four blue/orange wires has the three-hole connector on it.  Hopefully, it's not the wires from the speedometer.

[phil71]

This is as complete and as simple as I can make it. Start from scratch and make the connections just like this, and you'll be in business. You don't need to run a green wire all over the place, it just represents places that will need ground.

All orange and all blue connect to each other. Pretend your new lights have orange and blue wires coming out of them.
The bulb represents the indicator in the cluster, and reflects the re-wire you'll need to make it work. The diodes go in with the stripes exactly as I've shown here, and they come together , then are connected to the + of the bulb.

[gecko672]

Ok thanks for the drawing. That's very clear. Ill take a trip later for the supplies. Just out of curiosity. How has led lighting led to all this. What are the resistors for?  Ive read a few other articles and they mentioned the 3 prong electrical flashers but not the resistors. I don't know anything about electrical systems but willing to learn.

[gecko672]

Ok disconnecting the blue and orange from the instrument bulb does indeed split the two sides. Front rear left turn on together and the same for right. So my options for the instrument bulb are leave it disconnected. Or wire in the resistors as per Phil's drawing.
Will leaving the instrument bulb unplugged cause any harm? 

[Vinhead1957]

Am I missing something here'?  There should be another wire from the front lights that is the running lights. That is where the speedo/tach light should be tied to.   The rear lights are single filament only blinkers. The front should be dual filament one blinker one running circuit.

[phil71]

1) a 71 has no running lights.
2) even if it did have them, the new one-wire signals are not running lights, and those extra wires would get taped off.

[phil71]

You totally can run with no indicator. But, with 2 $2 diodes, you can easily restore its function later down the line

[phil71]

Ok thanks for the drawing. That's very clear. Ill take a trip later for the supplies. Just out of curiosity. How has led lighting led to all this. What are the resistors for?  Ive read a few other articles and they mentioned the 3 prong electrical flashers but not the resistors. I don't know anything about electrical systems but willing to learn.

Well, I'll try to keep this short, Light bulbs have a filament, that acts a lot like a jumper wire. So when you engage one side, it supplies the + to the indicator bulb, and the non-blinking side passes ground through it, completing the circuit. Then it reverses when you engage the other side.
  the LEDs are Light Emitting Diodes. A diode allows current to flow in only one direction, so it cant leak ground back to light the indicator.

[raymond10078]

The functional description is close.

First - you need to realize that the speedo turn signal bulb is not grounded.

On a stock bike, if you turn on the left signal, the left signal wiring provides power to the speedo bulb - and the speedo bulb then passes its current through the right side signals to ground.  The speedo bulb doesn't pass enough current to cause the right side bulbs to lights up.

In your case, the speedo bulb is passing enough current to right side lights.  This is because the original bulbs were two-23 watt bulbs - 46 watts total.  That calculates out to slightly less than 4 ohms to ground.  When you put on LED bulbs, the resistance to ground is much, much higher, and the current necessary to light the bulbs is now measured in milli-amps.  The speedo bulb provides the milli-amps necessary to light the LED bulbs.  I would've thought the speed bulb would have been a little dimmer - but maybe not . . . .

As phil71 has indicated, you can restore your speedo bulbs function with two diodes.  His wiring diagram for the end solution needs to be tweaked in one place (the ends of the two diodes need to be tied together).  The existing bulb is not grounded, so you'd be connecting either the blue or orange to ground, and then the other to the diodes.

[Fritz]

First - you need to realize that the speedo turn signal bulb is not grounded.

On a stock bike, if you turn on the left signal, the left signal wiring provides power to the speedo bulb - and the speedo bulb then passes its current through the right side signals to ground.  The speedo bulb doesn't pass enough current to cause the right side bulbs to lights up.

That's an interesting circuit. My 550 has two "speedo bulbs", so they are grounded directly. But Honda's single bulb setup is quite clever. I guess back in '71 there were not many LED turn signals on the market, so it was not a problem

I've just looked into some datasheets for diodes. A 1N4001 can handle up to 50V DC and 1A. That should be sufficient, they are cheap and tiny but the leads might be too thin to crimp a connector on them, so I'd look for 1N5400s which can handle 3A, have a lead diameter of 1.3mm / 0.52" and may be crimped to bullet connectors (ringed end directing to speedo bulb).

[phil71]

"As phil71 has indicated, you can restore your speedo bulbs function with two diodes.  His wiring diagram for the end solution needs to be tweaked in one place (the ends of the two diodes need to be tied together).   "

Actually, in the response, I noted they would be joined.. and I thought the fact they both terminate at the bulb + demonstrated that as well


If you're handy with a soldering iron, I'd make the diode "Y" off the bike, with some leads and shrink tube. If you really want to get clever, you can get bullet connectors and make a plug+play part to get the signal indicator working again.

[raymond10078]

Sorry phil71 - didn't read the words, only looked at the pic . . . .