Aftermarket speedo

[globe]

So I bought a cheap aftermarket speedo from e bay. Analogue not digital. When I wire it up, there is only a single negative wire that the high beam, neutral and indicators all go into. The issue I’m finding is that wiring them all up together causes issues, for example if I only touch the negative for the neutral light, the indicator and main beam only come on when bike is in neutral, similarly if I touch the negative for the indicators then the neutral is on permanently.

Any suggestions on how to start unwinding this little conundrum?

Cheers

[Honest Andy]

If you have a bad earth you'll get those symptoms.
Make sure your negative common earth actually goes to the frame with a clean connection. Don't just use the speedo mount either, because the power wont go through the steering head properly. There is bound to be a wired earth up there somewhere, use that and trace it back to where it attaches to the frame and make sure it's nice and shiny.

[globe]

If you have a bad earth you'll get those symptoms.
Make sure your negative common earth actually goes to the frame with a clean connection. Don't just use the speedo mount either, because the power wont go through the steering head properly. There is bound to be a wired earth up there somewhere, use that and trace it back to where it attaches to the frame and make sure it's nice and shiny.

Cheers mate, that makes sense, i was looking at the earth lead coming from the bike thinking there wasn't a connection on the speedo for an earth so I wondered where that should go, should I just wire the earth into the common negative would you suggest (or at least try it)?

One thing i forgot to mention is that the new speedo has LED lights, a bit of googling suggested diodes may help since the original is incandescent.


Don't just use the speedo mount either, because the power wont go through the steering head properly.

Sorry not really sure what you mean here about power running through the steering head. Do you mean this might be the earth and the mount will be a rubbish earth? Cheers

[Honest Andy]

There is a connection from your battery negative to the engine and frame, also known as earth or ground. So your whole bike becomes a negative that you can connect to, except the connection is less effective on the other side of bearings, rubber mounts, multiple bolted-together parts etc.

[neels]

If you have a wiring diagram for the bike and the speedo it would remove some guesswork.....

If the neutral switch is operated by switching the negative with constant +12V supply from the ignition, which is a pretty common way for them to work, a common negative from the speedo won't work and would cause the other lights to only light up when in neutral.

Not quite sure what you mean about negative to the indicators, there are a few different ways that the indicator light can work, but the indicator bulbs will be low enough resistance to light the led neutral light in the speedo when they're off.

With a common negative the only way it's going to work is to switch +12V to each of the bulbs, so you might need some extra bits in between the bike wiring and the speedo.

[globe]

If you have a wiring diagram for the bike and the speedo it would remove some guesswork.....

If the neutral switch is operated by switching the negative with constant +12V supply from the ignition, which is a pretty common way for them to work, a common negative from the speedo won't work and would cause the other lights to only light up when in neutral.

Not quite sure what you mean about negative to the indicators, there are a few different ways that the indicator light can work, but the indicator bulbs will be low enough resistance to light the led neutral light in the speedo when they're off.

With a common negative the only way it's going to work is to switch +12V to each of the bulbs, so you might need some extra bits in between the bike wiring and the speedo.

Thanks Neel, I have wiring details I will put them up. Re, your comments above. Yes the other lights are lighting up when in neutral as you have suggested. Negative for indicators, I mean by that the negative wire for the indicator display for the instrument cluster that comes from the bike and feeds into the new speedo wiring (if that makes sense)?

By extra bits are you thinking diodes to restrict the flow of the power to one direction? I have read that is a common issue on some retrofits.

[Honest Andy]

IIf the neutral switch is operated by switching the negative with constant +12V supply from the ignition, which is a pretty common way for them to work, a common negative from the speedo won't work and would cause the other lights to only light up when in neutral.

Good point. Can't have a neutral light in that case. Unless you add a relay or alter the wiring in the speedo.

[globe]

Good point. Can't have a neutral light in that case. Unless you add a relay or alter the wiring in the speedo.

HI Andy, excuse my ignorance but what would the relay do?

[Honest Andy]

Using a relay will allow you to get a switched positive for the speedo from switched negative of the neutral switch.
But don't worry about that now, this is all hypothetical until you try connecting it with a good earth.

[globe]

Wiring details

[globe]

I'm thinking this might be the solution, a reed switch??

http://forums.sohc4.net/index.php?topic=159933.0

[neels]

Wiring details
OK, so looking at that...the colours in the photo don't quite match the diagram but I can take a guess....

Orange is the +12V supply from the ignition for the neutral light.
Blue is the switched negative for the neutral(0V)
Yellow is the high beam +12V
Black/White is the 0V
2 blacks? are L/R indicators +12V

So this might work.....
337704

[globe]

OK, so looking at that...the colours in the photo don't quite match the diagram but I can take a guess....

Orange is the +12V supply from the ignition for the neutral light.
Blue is the switched negative for the neutral(0V)
Yellow is the high beam +12V
Black/White is the 0V
2 blacks? are L/R indicators +12V

So this might work.....
337704

Thanks! Do I need any sort of relay or just go into jay car and ask for a relay for 12v?

On the indicators on the speedo side there are two +ve in, the wires are two (orange and light blue) not a single striped wire, does this mean I still need the diodes?

Does your diagram show a wire running around the outside above the relay to?

[globe]

Something like this I’m guessing?

http://www.supercheapauto.co.nz/Product/Tridon-Mini-Relay-15-Amp-4-Pin/293187?menuFrom=1021626

[neels]

Thanks! Do I need any sort of relay or just go into jay car and ask for a relay for 12v?

On the indicators on the speedo side there are two +ve in, the wires are two (orange and light blue) not a single striped wire, does this mean I still need the diodes?

Does your diagram show a wire running around the outside above the relay to?

Don't need the diodes if the speedo has separate wires for the indicators, I read it as one wire for both left and right, two wires makes it easier.

You can either connect +12V to both sides of the relay, or use one of these...

http://www.supercheapauto.co.nz/Product/Tridon-Mini-Relay-22-Amp-3-Pin/293185

337705

with orange +12V connected to 1, blue from neutral switch to 2, and speedo green/red to 3.

[globe]

Don't need the diodes if the speedo has separate wires for the indicators, I read it as one wire for both left and right, two wires makes it easier.

You can either connect +12V to both sides of the relay, or use one of these...

http://www.supercheapauto.co.nz/Product/Tridon-Mini-Relay-22-Amp-3-Pin/293185

337705

with orange +12V connected to 1, blue from neutral switch to 2, and speedo green/red to 3.

That makes sense. I can’t wait until the weekend to give it a go now, cheers. Cracking resource this forum

[Honest Andy]

Yep that's it. Do what Neels said :yes: