dsltch Posted February 5, 2019 Share Posted February 5, 2019 hi..anyone out there know the voltage values on the speed sensor...having issues...have 2.0 volts at key on but does not increase when u driving.......checked all wireing...baffled...need help...just replaces sensor and speedo head.... Quote Link to comment https://www.bigmacktrucks.com/topic/55502-99-rd688-speed-sensor/ Share on other sites More sharing options...
turckster Posted February 8, 2019 Share Posted February 8, 2019 The speedo sensor has an ohm value, the circuit does not have voltage other than what the sensor itself creates when the truck moves. Depending on type of sensor, the ohms should be approx 100-200 ohms, typically around 150-170 ohms measured either from the sensor itself or from the VECU. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/55502-99-rd688-speed-sensor/#findComment-415179 Share on other sites More sharing options...
harold Posted August 25, 2019 Share Posted August 25, 2019 i have a 1998 RD model 688S mack with a E-7 Engine (non electronic). the speedometer works good but the odometer (Milege counter) stopped working after i reset the counter. is there any way i can repair the section that drives the odometer Re parts? without changing the speedometer which is very expensive !. my guess is that the motor that turns the odometer gear mechanism is defective. Quote Link to comment https://www.bigmacktrucks.com/topic/55502-99-rd688-speed-sensor/#findComment-430805 Share on other sites More sharing options...
JoeH Posted August 25, 2019 Share Posted August 25, 2019 You reset the trip meter and it caused the odometer to stop working? I'd try resetting the trip meter again, something could be sticking inside. Only other solution is to replace the speedometer and note the old odometer mileage somewhere like the door. Quote Link to comment https://www.bigmacktrucks.com/topic/55502-99-rd688-speed-sensor/#findComment-430814 Share on other sites More sharing options...
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