Question about Speedometer and VSS

Discussion in 'Electrical' started by Adamal47, Aug 3, 2010.

  1. Adamal47

    Adamal47 Active Member

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    The other day I was riding to work on the highway when I noticed that my speedometer was stuck on 55mph. I also notice that my turn signal weren't cancelling aswell. When I got home I took off the nut to get to the back of the speedo and in doing so I touched the harness and the pointer quickly dropped to 0 mph. The backlight works on the speedo but the pointer doesn't move and the odometer is blank. I did a search on here and see that the problem is probably the Vehichle Speed Sensor. What I haven't read on here is if that would also affect to odometer being completly blank. Would a new VSS make the odometer show numbers again?

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    Last edited by a moderator: Aug 15, 2010
  2. Hoople

    Hoople Account Removed

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    Are you saying the ignition was off when the pointer fell to zero. Or were you working with the circuits live.?

    I could tell you a lot more if I had the schematics for your '97 Softail. Can you upload a page or two of the prints showing the pin-out of the VSS and speedo head?
     
  3. Adamal47

    Adamal47 Active Member

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    When I reached my hand to the back of the speedometer the igniton was on but the engine wasn't running. The backlight was still on when it reset to zero. The speedometer is only about 6 months old. When I installed it I had to change the old style connections to the HD supplied deutcsh connections. It worked perfectly until this happened. Before this happened when I would turn on the ignition the speedometer would make a noise almost like a fuel pump priming it self on a car kind of sound just for a split second. Now I don't get this sound at all. I have a wiring diagram in PDF format. I don't know how to post it though.

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    Last edited by a moderator: Aug 15, 2010
  4. Hoople

    Hoople Account Removed

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    Since you have a three wire speed sensor you may want to try this. Hall Effect sensors are able to detect slow moving and stationary teeth. Jack the rear wheel off the ground. Place the bike in neutral. The VSS sensor has 3 leads which are 1) 12 volt supply,, 2) ground , and 3) sensor out. Take a DC voltmeter and place it between the Grd and "sensor out" pins. With ignition turned ON, you should be able to rotate the rear wheel and see the meter swing from Zero volts to +5 volts, back to Zero back to +5 volts over and over again. The voltage swing will be either zero to +5 or maybe zero to 9 volts, but it will be at LEAST 5.0v or some voltage greater than 5 volts.

    All pickup and speedo wires must remain hooked up while testing. Of course 1st verify you do have 12Volts on the Vss pickup. Then place your meter on the other 2 pins.

    The key is:
    Is the voltage greater than 5 volts DC & is it a clean swing from +5 to Zero to +5 to Zero over & over etc. (in other words a clean square wave from "0" to supply rail or +5)

    See what you read.