diode woes

[winguyjo]

i was getting a false neutral light on my 1975 which i cured, temporarily, by replacing the diode which was showing continuity in both directions. the fix worked briefly, but in very short order i was once again getting the false neutral light. testing the replacement diode i now showed no continuity in either direction. furthermore, none of the other 3 diodes on the bike show continuity in either direction.
i am testing them after removing them from the bike. is this the correct way to test a diode, or do they have to have voltage running through them during testing ? i would think that if the other 3 are also bad i would have problems with the high/low beam switch, the kill switch and the start button, all of which appear to run through a diode.

[winguyjo]

upon further investigation ... it seems there is a diode function on the multimeter ... ... who knew ?

upon further, further investigation ... after letting the bike cool down for 45 minutes, neutral light is functioning properly, and starter will function when bike is in gear and the clutch lever is pulled in, as it should.

can a diode fail intermittently, like when things are hot, and then function properly when cool ?

[winguyjo]

to answer my own question ...

with some searching i learned that a) a diode does not have to have power running through it when testing and b) when testing a diode using the "diode" section of the ohmeter, you should get continuity in one direction, with a resistance reading of between 0.4ohms and 0.6ohms, and an "open" circuit when you reverse the leads.

i still don't know whether a diode can fail when warm but still work when cold, because i replaced the "replacement" diode before i learned how to properly test them .

[DenverWinger]

Diodes either work, or are shorted, or are open. Once they stop working they stay that way. Best to test them out-of-circuit, one lead or both disconnected. The connected circuitry can fool the meter.

Got to be some other temperature-related issue, possible there's a wire on the ground side of the neutral light that's rubbed thru and is intermittently letting the light come on? Or maybe the Transmission Neutral switch is sticking?

Neutral switch in my 1100 was stuck on for many many years, I simply removed the Neutral light bulb from the instrument cluster so I didn't have that bright green light in my face all the time, especially at night. I'm quite accustomed to finding Neutral without the green light. I think it's unstuck now, though. I noticed the starter doesn't work with bike in gear anymore unless I pull the clutch (like it's supposed to do) 'cause sometimes I don't put in neutral when I park. Maybe I'll put the light bulb back in and see....

To get to the neutral switch on the '80 GL1100 the engine has to come out. It's on the lower right side of the engine block under the cylinder head, obstructed by the frame. Not worth the bother. I think the GL1000 has same switch.

[winguyjo]

thanks for the feedback, denver. learning how to test these things has been an important step forward in my high-paying career as a gl1000/1100 resurrector .

one thing i forgot to mention is that somewhere during this process, i pressed the start button and the neutral light went out. so my next move before a thorough warm-up and test ride is going to be disassembling and cleaning that switch. in fact, i am now convinced that when bringing these 'long-term sitters' back to life, the disassembly and cleaning of all handlebar switches should be on the 'to-do' list.

[DenverWinger]

Nothing in the Start switch that could cause the Neutral light to come on... Still a good idea to clean it and the rest of them.

Start switch has two sets of contacts, one normally closed (for headlight) and one normally open (for start relay). When you press start the closed contacts open, and the open contacts close.

I need to do that to my 1100, sometimes after starting the headlight stays off, and I have to fiddle the start button to get it to come on again.

[WingAdmin]

to answer my own question ...

with some searching i learned that a) a diode does not have to have power running through it when testing and b) when testing a diode using the "diode" section of the ohmeter, you should get continuity in one direction, with a resistance reading of between 0.4ohms and 0.6ohms, and an "open" circuit when you reverse the leads.

i still don't know whether a diode can fail when warm but still work when cold, because i replaced the "replacement" diode before i learned how to properly test them .

Think of a diode as a one-way valve. It lets current flow in one direction, and not the other.

ANY electronic device - transistor, diode, etc. can fail when warm, that's actually very common. In fact, it is a common electronic diagnostic method to use a "cold spray" to spray individual electronic components to find one that is failed when warm, but works when cold.

[dummysales]

Speaking of diodes on the 1100 Aspencade, where do you buy them? I'm in definite need of one. Smoke is not a good indicator.
waj

[Rambozo]

Speaking of diodes on the 1100 Aspencade, where do you buy them? I'm in definite need of one. Smoke is not a good indicator.
waj

You can still get them from Honda. 31700-124-003
Or GoldWing Parts has them for about half what Honda gets.
https://www.goldwingparts.com/products/ ... utch-diode
And since Honda used those on like every bike they made, there is always ebay.
https://www.ebay.com/itm/185078342185

[dummysales]

Thank you very much. Waj