Patrick Sweeney Posted January 10 Share Posted January 10 I have a 1989 R688ST. I recently replaced the transmission from a 9 speed Fuller to a 13 speed Fuller. The original speedometer was cable to the rear of the transmission. The new 13 speed is sensor on the yoke. The new electronic speedometer is five wires: power, ground, dash lamp, and 2 sensor wires. I have good ground and power and I get the display for the speedo. I also replaced the sensor on the yoke. Everything is new. The problem I am having is that when the speedometer is plugged in, it will go crazy, to 45MPH, then to 85, the back to 25 etc. Any help would be great. I can't figure out what I'm doing wrong. I believe I have everything connected correctly. Quote Link to comment https://www.bigmacktrucks.com/topic/73741-electronic-speedometer-not-working/ Share on other sites More sharing options...
Joey Mack Posted January 10 Share Posted January 10 (edited) Are there dip switches on the back of the speedo? Edited January 10 by Joey Mack Pore cell fone sperring Quote Link to comment https://www.bigmacktrucks.com/topic/73741-electronic-speedometer-not-working/#findComment-544880 Share on other sites More sharing options...
mechohaulic Posted January 10 Share Posted January 10 with the statement "it will go crazy", is this soon as things are plugged in = or when unit is moving ? does it happen with key off ?? Quote Link to comment https://www.bigmacktrucks.com/topic/73741-electronic-speedometer-not-working/#findComment-544881 Share on other sites More sharing options...
Patrick Sweeney Posted January 10 Author Share Posted January 10 It will go crazy when its plugged in. Brand new Speedo. I have the dip swithes set. But they only control the accuracy of the speedometer is what I'm told. Quote Link to comment https://www.bigmacktrucks.com/topic/73741-electronic-speedometer-not-working/#findComment-544887 Share on other sites More sharing options...
Patrick Sweeney Posted January 11 Author Share Posted January 11 It will go crazy when the ignition is turned on. So when power is put to the speedometer. Quote Link to comment https://www.bigmacktrucks.com/topic/73741-electronic-speedometer-not-working/#findComment-544920 Share on other sites More sharing options...
Geoff Weeks Posted January 29 Share Posted January 29 1st check the power and ground for good connection, 2nd check the sensor wires they should be a twisted pair and/or shielded. If not they may be picking up stray signals from something else. Also there are different impedance pick-ups, the wrong one usually just doesn't work. Sometimes swapping wires on the sensor circuit helps if one side of the sensor is grounded. If all else fails, run a twisted pair in a shielded cable to the back of the trans to keep out stray signals. Quote Link to comment https://www.bigmacktrucks.com/topic/73741-electronic-speedometer-not-working/#findComment-545772 Share on other sites More sharing options...
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