Diode Install for '79 Special Single Turn Signal Indicator

[patk12345]

So, here's the situation. I tried to convert my turn signals to LED bulbs on my bike, which I thought was an '80 Special, but turns out to be an '80 Standard with the lights and cluster from a '79 Special. The problem is that the '79 Special cluster has a single turn signal indicator, similar to that of the XS 650's and 400's. Because of the lower draw of the LED bulbs, the excess voltage usually used by the incandescent bulbs, is feeding back through the single signal indicator.



The solution,appears to be the installation of diodes, so that the excess voltage doesn't feedback through the single signal indicator. Apparently Mike's XS used to sell a kit specifically for this purpose.

The question, is where exactly in the wiring to put these diodes?

I traced the wiring through the cluster and inside the headlight and down to the chassis where I found a flasher relay, just below the fuse box, under the right side cover. This controls the blinking of the single signal indicator. I'm wondering if this might possibly be where those diode need to be. This is just a guess.



Thanks to Cy, and bikerphil for their help on this so far!

[DAVINCI]

Maybe I'm missing it, but I don't understand your problem. What exactly is happening when you hit the turn signal switch?

[patk12345]

@Davinci
With the LED's installed, if you signal Left or Right, all four bulbs come on but don't flash, and if you turn the hazards on all four bulbs flash, but only at half intensity. After discussing it with Cy and bikerphil, the conclusion seems to be that because the LED's draw less current than traditional bulbs, that the excess amperage is feeding back through the signal indicator because on the 79 Special cluster, it's only one bulb for both directions, not two like the other XS11 clusters. The XS 650's have the same single bulb signal indicators, and at some point Mike's XS sold a kit to solve the feedback issue using diodes, which don't allow the voltage to feedback trough the signal indicator bulb.
I'm trying to determine exactly where these diodes would need to be wired in, to stop said feedback.

[crazy steve]

Pat, it sounds like you have several things going on here (from also reading your flasher thread).

First, the one side not flashing/flashing at a different rate is due to a poor connection or connections in the circuit, so you need to address that. Poor grounds are the usual culprits, but look at everything.

Next, if you remove the instrument panel indicator light, do the turn signals then work correctly? If they do, then we'll deal with the dash light. But if they don't, you still have issues in the wiring and need to fix that.

Now, if you've got everything working right with the dash indicator out, let's fix that. As it is, the bulb is connected to the 'power' wire from each side; should be a chocolate and a dark green. Note that there's no 'ground'. A bit of rewiring is needed besides adding the diodes. Disconnect both wires from the lamp, and take one to ground (preferably the one connected the outer shell, not the center contact). Install a diode on each of the turn signal wires (getting 'direction' right), then connect the diodes to the light. This will allow power 'in' to the lamp and to ground, but will prevent feedback to the other side. Below is a simple diagram to clearly show this.

[IMG][/IMG]

I'd try to install the diodes in the light cluster to protect them; put some shrink tube over them too. Hopefully I have the diode 'direction' shown right (always have trouble with that for some reason ); if the light doesn't come on, the diodes are backwards. Use a diode rated for at least .5 amp, 1 amp would be better...

[patk12345]

@Steve
Thanks a million! I knew you would be the guy to go to. I believe it may indeed be a grounding issue, as the housing on the right front turn signal is not firmly mounted to it's stem, I'm not quite sure how to get that the seem between the stem and the housing tighter, as it appears to be a friction fit. I suppose worst case scenario, I can always run a ground wire through the stem to the housing, along side the positive lead.

As far as your diagram goes, I'm pretty sure you have the diodes facing the right way, at least from what I can remember from my Electronics for Audio class back in college.

Now I just need to find some good diodes, but I'll probably have to settle for what I can find at Radio Shack.

[cywelchjr]

Pat, it sounds like you have several things going on here (from also reading your flasher thread).

First, the one side not flashing/flashing at a different rate is due to a poor connection or connections in the circuit, so you need to address that. Poor grounds are the usual culprits, but look at everything.

Next, if you remove the instrument panel indicator light, do the turn signals then work correctly? If they do, then we'll deal with the dash light. But if they don't, you still have issues in the wiring and need to fix that.

Now, if you've got everything working right with the dash indicator out, let's fix that. As it is, the bulb is connected to the 'power' wire from each side; should be a chocolate and a dark green. Note that there's no 'ground'. A bit of rewiring is needed besides adding the diodes. Disconnect both wires from the lamp, and take one to ground (preferably the one connected the outer shell, not the center contact). Install a diode on each of the turn signal wires (getting 'direction' right), then connect the diodes to the light. This will allow power 'in' to the lamp and to ground, but will prevent feedback to the other side. Below is a simple diagram to clearly show this.

[IMG][/IMG]

I'd try to install the diodes in the light cluster to protect them; put some shrink tube over them too. Hopefully I have the diode 'direction' shown right (always have trouble with that for some reason ); if the light doesn't come on, the diodes are backwards. Use a diode rated for at least .5 amp, 1 amp would be better...

That looks right from my memory what with suffering from CRS and all. I'm pretty sure those are drawed the right way as well, IIRC you draw the triangle facing towards the negative pole of the circuit. But that's how I remember it being setup, and is why it doesn't work with the LED's because with the single light setup the light is lit by grounding through the bulbs on the unlit side. With LEDs this is enough to light them.

[patk12345]

@Cy
Hey Cy, thanks for helping me to diagnose the problem in the first place. The CRS can't be all that bad, as you remembered the basic premise of the problem and the solution.

Any thoughts on how to get a tighter grip between the flasher housing and it's stem, in order to get a better ground?

[patk12345]

One more thing I'm still not sure on there are two flasher relays on the bike, the one under the seat by the battery, and the one under the fuse panel inside the right side cover. Which one does the no load flasher relay replace?

[crazy steve]

The one by the battery is the four-way, the one by the fuse panel is the turns and the one you need to replace. Actually, with all LEDs, you should replace both with electronic flashers.