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Discussion Starter · #1 · (Edited)
Hi 馃槆

This thread does mainly what it does on mine, the neutral light goes on each time I press the clutch. At first sometimes it also turn on in 2nd gear or 1st so it confuses a little, I think there was when the diode started to die.

Tested the clutch switch in the left handlebar and works (when pressed it get continuity).
Also test the Clutch Diode as shown in the manual, should get ohms readings in one way and not the other (mine reads both ways, and have continuity.)

I disconnect the Clutch Diode from the connector, test continuity between the two contacts in the connector and pressed the clutch switch at handlebar and seems OK (I mean releasing there is no continuity, pressing there is continuity, pressing read about 0,024 ohms in 200 scale, hope doing it right way...)

I get confused because there are some that costs about 60us to 17us, and ofcourse there is no part avaiable where I live, just similar and the seller dont know a thing.

These are the parts 31700-124-003, 31700-124-008, but seems there are lot of other bike models compatible. The diode reads S3H-02 (and 6.3 near the contacts) does it means its 6v? what does S3H-02 means?

Whats the function of this thing?

Thanks as always for reading!

(I promise not to open the engine this time... :poop:(y))

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'08 Spirit 750
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Diodes stop current in one direction, but allow it to flow in the other direction (minus an average .7 volts it takes to overcome a natural "blockage" that way) on circuits that flow current both ways. Here they're used to limit the polarity of the circuit to function in one direction only, so that it becomes a "tell tale" circuit.

If they no longer block the direction they should they've failed, and're allowing current to flow in the wrong direction as well as the right one. The only fix is to replace'em with a good one, that's why these're engineered to simply plug in.
 

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Discussion Starter · #3 ·
Diodes stop current in one direction, but allow it to flow in the other direction (minus an average .7 volts it takes to overcome a natural "blockage" that way) on circuits that flow current both ways. Here they're used to limit the polarity of the circuit to function in one direction only, so that it becomes a "tell tale" circuit.

If they no longer block the direction they should they've failed, and're allowing current to flow in the wrong direction as well as the right one. The only fix is to replace'em with a good one, that's why these're engineered to simply plug in.
Thanks Beggar! I had to have a look in wikipedia for tell-tale circuit... and its right for me "the idiot light" damn, now I doubt if it is working good, it knows when I press it :rolleyes:

I will replace it, can get about 6 sellers of this kind of diode (same polarity) here but dont know if the diode needs some more specification to have in mind... does it mean something the S3H-02 and 6.3 text? is it a 6 volt diode? (if it is 6 volt and the bike is 12v... getting lost here... or is it just a factory coded text down there?)
 

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Discussion Starter · #5 ·
A circuit will only use the amount of the 12 volts that it needs. This circuit just lights a bulb, and that bulb likely needs just five volts. Add the .7 volt to overcome the diode bias, and that's 5.7 volts needed to light the bulb. Add another .6 volt for a bit of insurance, and to be able to use a readily available "off the shelf" (read; cheap & handy ;)) diode, and you're at the 6.3 noted on the base.
Thank you very much! thanks for the detailed explanation! 馃檹
 

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Discussion Starter · #7 · (Edited)
Reread your initial post, and at .024 ohms forward I doubt your diode's gone bad. In addition to which it's not on a segregated tell tale circuit of its own.

I'd look into the possibility of a stuck (on) neutral switch.
(there! I recheck your last post... what it gives 0,024 ohms in scale 200 in the first post, it is from the connector to the wire harness (not the diode), I think the resistance read here is the wiring to the handlebar clutch switch?)

Mmm, I test and re-test now just the diode (not the connector to the wire harness), and it have continuity both ways. Also recheck the scale is in ohms 200 and the diode it measures 0.2 both ways.

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'08 Spirit 750
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I apologize for the misinformation, my fault. The purpose of the diode in this diagram is not clear to me. If they're using the diode "drop" to light the neutral bulb, the connections for the bulb aren't shown.

That said, any diode should pass no current in one direction, and a slight loss of current in the opposite direction. If you're showing any continuity in both directions it should be replaced.
 

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Discussion Starter · #9 ·
I apologize for the misinformation, my fault. The purpose of the diode in this diagram is not clear to me.

That said, any diode should pass no current in one direction, and a slight loss of current in the opposite direction. If you're showing any continuity in both directions it should be replaced.
Nono, thanks you very much anyway! will get a new one and repeat the test and update the results here.

The diode purpose in this diagram... still a mistery o_O

Here I found a guide for newbies on how to test diodes and seems easy even to me :geek:
 

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It's used to provide an either/or type scenario, If the bike is in neutral the start button grounds through the neutral light and you press start, it cranks, with or without the clutch lever being pulled, If it's not in neutral, you have to pull the clutch to provide the ground for the start button.


Pretty much any diode rated for more than 1 amp and more than 12v should be fine, They're merely acting as a current check valve in these circuits, An industry number 1N4002 should be heavy enough, Or get a 1N4004 for good measure. less than a dollar each at some place like Digikey.com
 

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1983 Honda vt750 Shadow
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Here is from the 1983-1985 manual. Same system but laid out a little different and shows the bulb.
 

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Actually it would still start as long as the neutral switch is working, the diode is tied in after the bulb filament and prevents the neutral light 12v from backfeeding into the clutch switch wiring and lighting the neutral light when the clutch is pulled and it's not in neutral. It's the negative side of the solenoid windings getting two different paths to ground. Through the clutch switch ground or the neutral switch ground.

Just wait till you get a newer one with the side-stand switch included in the safety circuits...
 

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'08 Spirit 750
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Side stand on my '08 also cuts the engine if you put'er in gear while down, or down while in gear, clutch position not with standing.

Frankly getting a bit tired of that, as I'm long used to putting'er in gear prior to kicking the stand up. But I understand the reasoning (electric start in stead of kick), so guess I'll just adapt.
 

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Discussion Starter · #20 · (Edited)
Actually it would still start as long as the neutral switch is working, the diode is tied in after the bulb filament and prevents the neutral light 12v from backfeeding into the clutch switch wiring and lighting the neutral light when the clutch is pulled and it's not in neutral. It's the negative side of the solenoid windings getting two different paths to ground. Through the clutch switch ground or the neutral switch ground.

Just wait till you get a newer one with the side-stand switch included in the safety circuits...
In VT700 1986 I dont have a side-stand switch, just handlebar clutch switch, left side crank "inside engine" clutch switch (there comes 3 cables, 1 for clutch, 1 for overdrive and 1 for oil pressure)

On friday I am getting a 31700-124-003 clutch diode replacement made in Thailand :rolleyes: (its not original, but same honda code) and it says 6 volts not 12 volts :oops: hopefully will be the right one.
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