Neutral Diode - Questions


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TheRepoGuy
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Motorcycle: 1985 GL1200I Interstate
1985 GL1200A Aspencade

Neutral Diode - Questions

Post by TheRepoGuy »



Afternoon Folks -
Since my service manual is STILL a bit delayed for some ungodly reason I need a little help with this one.

The original part is made by Stanley shows a number stamped on it of 3607H1; I was trying to see if I can get the part locally and there’s an electronic store close to me which does stock diodes but they’re a barrel type not so much this block type.

Can anyone provide the specs on the aforementioned diode by some chance so I can see if these electrical gurus might have it? I’d gather it’s a 12v given the system but ya never know. TIA
Nate





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WingAdmin
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Re: Neutral Diode - Questions

Post by WingAdmin »

The diode shunts power to ground if the clutch is not pulled in (but the transmission is in neutral):

Starter Circuit
Starter Circuit

If your starter relay was wired in wrong, and presented a dead short instead of the relay coil, it will have put a massive amount of current through that diode, and that will let out the magic smoke - as you discovered. It will also melt wires - also as you have discovered.

A diode is a diode. Take your ohm meter and measure the resistance of your starter relay coil.

Take that measurement (in ohms) and divide 14 by it. So if you measure 10 ohms, then divide 14 by 10, which gives you 1.4.

That result is the amount of current that will be going through the diode. Whatever that value is, double it. Now find a diode that is rated for that. Do a search for "high current diode" and find one that is rated for at least 2.8 amps (or whatever the result is from your measurement). It shouldn't cost more then $5-$10, depending on the size.

While not the correct way to do it, I've cheated when I didn't have the correct value diode, and wired several in parallel to get the rating I needed. For instance, I would take three 2-amp diodes, wire them in parallel, to replace a 6 amp diode. There are drawbacks to this, but for this application it should work fine.

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TheRepoGuy
Posts: 66
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Motorcycle: 1985 GL1200I Interstate
1985 GL1200A Aspencade

Re: Neutral Diode - Questions

Post by TheRepoGuy »

WingAdmin wrote:
Mon Jun 10, 2019 4:08 pm
The diode shunts power to ground if the clutch is not pulled in (but the transmission is in neutral):

Starter Circuit.GIF

If your starter relay was wired in wrong, and presented a dead short instead of the relay coil, it will have put a massive amount of current through that diode, and that will let out the magic smoke - as you discovered. It will also melt wires - also as you have discovered.

A diode is a diode. Take your ohm meter and measure the resistance of your starter relay coil.

Take that measurement (in ohms) and divide 14 by it. So if you measure 10 ohms, then divide 14 by 10, which gives you 1.4.

That result is the amount of current that will be going through the diode. Whatever that value is, double it. Now find a diode that is rated for that. Do a search for "high current diode" and find one that is rated for at least 2.8 amps (or whatever the result is from your measurement). It shouldn't cost more then $5-$10, depending on the size.

While not the correct way to do it, I've cheated when I didn't have the correct value diode, and wired several in parallel to get the rating I needed. For instance, I would take three 2-amp diodes, wire them in parallel, to replace a 6 amp diode. There are drawbacks to this, but for this application it should work fine.
Thanks much! If I can find the right ones I’ll make it happen, if not I’ll bite the bullet and order one.

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TheRepoGuy
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Motorcycle: 1985 GL1200I Interstate
1985 GL1200A Aspencade

Re: Neutral Diode - Questions

Post by TheRepoGuy »

Alright - the wires going to the diode were cooked through most of the harness clear up to just before the plug for the rectifier. Wires are a Green with red tracer and a light green with red tracer.

Given they were melted at the plug, which side would be the anode versus the cathode?

In the aforementioned diagram it doesn’t show color codes so I have no bloody clue what’s what 😣

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virgilmobile
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Re: Neutral Diode - Questions

Post by virgilmobile »

Assuming that you have corrected the original problem...
This is cheating but..
Leave the bike in gear(not neutral)
Turn on the key.
Attach the diode..pull in the clutch lever.
If the neutral lamp lights up reverse the diode wires.
If the neutral lamp stays off it's correct.
In gear you should be able to crank the bike with the clutch lever pulled in.

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TheRepoGuy
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1985 GL1200A Aspencade

Re: Neutral Diode - Questions

Post by TheRepoGuy »

virgilmobile wrote:
Wed Jun 12, 2019 10:41 am
Assuming that you have corrected the original problem...
This is cheating but..
Leave the bike in gear(not neutral)
Turn on the key.
Attach the diode..pull in the clutch lever.
If the neutral lamp lights up reverse the diode wires.
If the neutral lamp stays off it's correct.
In gear you should be able to crank the bike with the clutch lever pulled in.
I’ll find out - had to order the diode anyway dammit ha! Can’t find those locally
Nate

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virgilmobile
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Re: Neutral Diode - Questions

Post by virgilmobile »

Without the diode you can still run the bike.You just can't start it in gear

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TheRepoGuy
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1985 GL1200A Aspencade

Re: Neutral Diode - Questions

Post by TheRepoGuy »

virgilmobile wrote:
Wed Jun 12, 2019 11:31 am
Without the diode you can still run the bike.You just can't start it in gear
Agreed - However I’m really giving this old girl everything she should have to be mostly all original with a few added perks. Hopefully while not the prettiest girl on the block she will run like a damn champ when I’m done!

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virgilmobile
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82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Neutral Diode - Questions

Post by virgilmobile »

On mine,the few perks were.
New timing belts
Carb modify to overcome the 2500rpm stumble
Charging circuit modifications for a stable circuit.
More power to the coils (voltage drop problem)to improve spark.
Repair to the loud ticking fuel pump to stop it's impending failure.
Very accurate rebuild and alignment of the front forks for a nice ride.
Keep us posted.



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