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post #1 of 10 (permalink) Old 03-28-2018, 12:48 AM Thread Starter
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eBay digital speedometer question

Has anyone bought one and installed it? I just recently got one and having trouble wiring it up.
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post #2 of 10 (permalink) Old 03-28-2018, 10:46 AM
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Be more specific about having trouble wiring it up.


1981 KZ750
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post #3 of 10 (permalink) Old 03-28-2018, 02:30 PM
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Be more specific about having trouble wiring it up.
Aye. What wires does it have, and which of those wires have you tried to attach where?

1992 US-nonCA * tuxedo mod * r/r relocated

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post #4 of 10 (permalink) Old 03-28-2018, 07:03 PM Thread Starter
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Quote:
Originally Posted by One1 View Post
Be more specific about having trouble wiring it up.
Quote:
Originally Posted by Thorn View Post
Quote:
Originally Posted by One1 View Post
Be more specific about having trouble wiring it up.
Aye. What wires does it have, and which of those wires have you tried to attach where?

It has a ground wire – no problem there
It has any power wire – hooks up to the ignition switch, no problem there
Got a memory/power wire – hooks up directly to the battery, no problem there

Turn signals work with no problem as well as the neutral indicator light

Where I’m having a problem is with the tach. It is very slow to respond and sticks.
Fuel gauge is working, but I do not think it’s accurate.
And my highbeam indicator light is constantly on.
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post #5 of 10 (permalink) Old 03-28-2018, 07:05 PM Thread Starter
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This is the speedo/tach I bought on eBay
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post #6 of 10 (permalink) Old 03-28-2018, 08:41 PM
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Well, it sounds like you have it wired up correctly, if you're getting any response from it at all.
For the fuel gauge, the fuel level sensor wire is the white one.
For the tach, the black wire is the signal wire and is shorted to ground every time one (can't remember if it's the front or the rear) coil fires.

I'm just spitballing, and maybe someone else has a better idea, that maybe the IC box that controls the spark timing doesn't provide a clean square wave signal on the black wire, which may be causing problems for the digital tachometer? You might be able to find some sort of filter that would clean up the signal a bit before it hits the tach. Maybe just cleaning up the connectors at the IC box and ground would give you a more decisive path to ground more stable signal.

1992 US-nonCA * tuxedo mod * r/r relocated

Vulcan slang for newcomers
Service Manual Download
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post #7 of 10 (permalink) Old 03-28-2018, 09:15 PM Thread Starter
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Quote:
Originally Posted by Thorn View Post
Well, it sounds like you have it wired up correctly, if you're getting any response from it at all.
For the fuel gauge, the fuel level sensor wire is the white one.
For the tach, the black wire is the signal wire and is shorted to ground every time one (can't remember if it's the front or the rear) coil fires.

I'm just spitballing, and maybe someone else has a better idea, that maybe the IC box that controls the spark timing doesn't provide a clean square wave signal on the black wire, which may be causing problems for the digital tachometer? You might be able to find some sort of filter that would clean up the signal a bit before it hits the tach. Maybe just cleaning up the connectors at the IC box and ground would give you a more decisive path to ground more stable signal.
Thanks for the help!

Question though, I noticed on the wiring diagram that there are three wires on the tach and three wires on the fuel gauge. One is for the sensor, one is for ground, and one is brown that leads to the junction box/ignition switch. I do not have a spot to put that wire on my new Speedometer. Question is, is that needed for the fuel gauge and the tach or should I Cap it?
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post #8 of 10 (permalink) Old 03-28-2018, 10:10 PM
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Those brown wires are the +12v lines when the ignition switch is "on". You said you were already pulling power from the ignition switch to the new module, so those leads are just extraneous now. Cap 'em.

1992 US-nonCA * tuxedo mod * r/r relocated

Vulcan slang for newcomers
Service Manual Download
Wiring Diagram + annotations * still undergoing revisions, but still more useful than the generic one. Let me know if you find mistakes or think something additional should be added
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post #9 of 10 (permalink) Old 03-28-2018, 11:53 PM
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Only caveot to lack of power wires is if you're on an underpowered line. You may not be on a line supplying proper amperage or voltage into the cluster. Check and verify voltage with everything on and running. If you have a voltage drop at the unit with it on, but proper voltage coming in with it off, your supply in line isn't keeping up with demand. A weak ground can simulate this effect.


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1988 Vulcan VN750 (red)
2005 Vulcan VN750 (silver)
(2) 1994 Vulcan VN750 (red)

Engineering solutions for the VN750 Community.
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post #10 of 10 (permalink) Old 03-29-2018, 10:47 AM Thread Starter
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Quote:
Originally Posted by Thorn View Post
Those brown wires are the +12v lines when the ignition switch is "on". You said you were already pulling power from the ignition switch to the new module, so those leads are just extraneous now. Cap 'em.
Quote:
Originally Posted by One1 View Post
Only caveot to lack of power wires is if you're on an underpowered line. You may not be on a line supplying proper amperage or voltage into the cluster. Check and verify voltage with everything on and running. If you have a voltage drop at the unit with it on, but proper voltage coming in with it off, your supply in line isn't keeping up with demand. A weak ground can simulate this effect.
Thanks guys. A lot of great help. Hopefully I can figure out the issue this weekend because it’ll be nice to ride here in the SF Bay Area
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