2008 Fat Boy speedometer not working

Discussion in 'Electrical' started by jlkoko, Jul 31, 2015.

  1. jlkoko

    jlkoko New Member

    I have a 2008 Fat Boy w/ ~15k miles. When I started it for a recent ride, the speedometer LCD was blank (no clock, no odo). I figured it was a fuse and would take care of it when I returned. When I got back, I checked the instrument fuse and it was fine; I swapped fuses to be sure. However, I also noticed that the speedo dial was now stuck at 60. I pulled the speedo and tried it in a buddy's wiring harness; my speedo showed nothing (and was still stuck on 60) when we turned the ignition on. So, at that point I assumed that it was the speedometer unit. I should have tried his speedo in my wiring harness but he was reluctant to do so.

    Rather than pay $200 for the stock unit, I purchased a new combination speedo/tach from H-D. It is a model 70900070B and is supposed to work on a variety of models (including mine) that have a 5" speedo. The instructions tell me to first marry the new unit up w/ the ECM thru the data link port under the seat. Following the instruction, I plugged in the new unit tot eh data link port, turned on the run switch and the ignition to begin the calibration process. The LCD on the new speedo showed CAL then went to NO SPD. The trouble shooting instructions do not say anything about what to do if you get the NO SPD display.

    My old, inoperative speedo was still plugged into the harness so I'm wondering if there is something else wrong. It seems like the system is looking for the old speedometer but can't find it. Did something electrical happen that also caused a problem w/ the old speedometer? I also noticed on the back of the new speedo/tach the number is 70900068B but the box has 70900070B. I don't know if that has something to do with it our not; 68B may just be the speedo part num and the 70B indicates a 'kit'; the kit came with a speedo and a transfer cable.

    Does anyone have any suggestions or have experience w/ this? Thanks.
  2. Breeze3at

    Breeze3at Well-Known Member

    Just a guess, but I think the old speedo needs to be removed from the harness. Even if inoperable, there is likely some wire/signal that the ECM is seeing through the data port connection.
  3. Jack Klarich

    Jack Klarich Guest

  4. jlkoko

    jlkoko New Member

    Thanks for the feedback, but the original speedometer MUST remain in place (look at note 3 on page 3 of the instructions....remove the old speedo then install the new speedo). Seems like the ECM can only be married to one speedo thru the VIN. I'm not sure, but I think the conversion process may wipe the VIN from the old speedo. Since mine is no longer working, when I plug the new one into the data link, it can't see the old b/c it is dead, so it thinks it was removed.

    I called H-D customer service (which is not really tech support). They told me that a dealer has to send it back to H-D to have it calibrated/matched. I thought that was unusual so I called a dealer. The dealer told me that, on newer bikes they have the software to read the ECM and can transfer the miles and VIN to the new speedo.

    So, it looks like I have to take it to a dealer.....they are probably the only ones that can read the ECM.