cvdell Report post Posted November 3, 2020 Last trip, for first time, my speedometer almost stopped working. At low speeds it stayed on zero. At 50 mph it would read 3 - 4 mph (I've had the coach 15 yrs, know how fast I'm going by the tach). All other gauges were functional. Cruise control worked. Odometer turned over, but at very reduced rate - probably corresponding to the reduced reading from the speedometer. On the return trip 3 days later, speedometer worked properly. Chassis is 1998 Freightliner XC with ISB/MT643 powertrain. I looked at wires under dash - nothing was obviously loose (but, there are several dozen wires there, no idea which drives the speedometer). Suggestions? Share this post Link to post Share on other sites
richard5933 Report post Posted November 3, 2020 Check for a loose ground lead to the speedo or the cluster. Find where your sending unit is on the transmission and check for connections there. Share this post Link to post Share on other sites
manholt Report post Posted November 3, 2020 Your speedometer is air controlled, check the L fitting for leak, it's made of plastic! Share this post Link to post Share on other sites
dickandlois Report post Posted November 3, 2020 3 hours ago, cvdell said: Last trip, for first time, my speedometer almost stopped working. At low speeds it stayed on zero. At 50 mph it would read 3 - 4 mph (I've had the coach 15 yrs, know how fast I'm going by the tach). All other gauges were functional. Cruise control worked. Odometer turned over, but at very reduced rate - probably corresponding to the reduced reading from the speedometer. On the return trip 3 days later, speedometer worked properly. Chassis is 1998 Freightliner XC with ISB/MT643 powertrain. I looked at wires under dash - nothing was obviously loose (but, there are several dozen wires there, no idea which drives the speedometer). Suggestions? I have had the same issues or related problems with an older Freightliner chassis. There is a possibility of a poor connection at the speed sensor ( it has 2 sensors mounted in the assembly.) ATF can leak through the assembly pins mounted in the sensor. Remove the connection from the sensor located in the Transmission. Clean the connection and socket with CRC. Ware eye protection, getting the spray in your eyes is no good ! The second issue I have experienced is the speedometer reading to fast at a preset engine speed / Tachometer. Hear can become an issue. The third item that can cause the problem is noise generated in the voltage regulator diodes due to heat. Good luck and keep us in the loop. Rich. Share this post Link to post Share on other sites
