abyrd Report post Posted May 13, 2018 The Tach on my 2004 Holiday Rambler Endeavor with Cummins ISC failed when cruising down the road. All was fine cruising up Cabbage Hill grade in eastern Oregon and smelt slight odor, look down at instrument cluster all good except tachometer was reading "0". Anyone have experience with failure of tachometer, I assume signal is from engine ECU. I believe the instrument cluster meters are manufactured by VDO. Anyone have any experience or lead on repair facilities? Thanks, Jim Share this post Link to post Share on other sites
manholt Report post Posted May 13, 2018 Jim. You have REV group in Coburn, OR. Call Tech dept., they probably have what you need in stock. The odor, could also be a shorted wire...can you get at the back side of Tack to check wires? Share this post Link to post Share on other sites
rsbilledwards Report post Posted May 13, 2018 REV 877 466 5226 or 800 435 7345 Share this post Link to post Share on other sites
obedb Report post Posted May 13, 2018 Must have a really big engine of you were "cruising up Cabbage." 😎 Share this post Link to post Share on other sites
abyrd Report post Posted May 13, 2018 No signs of damaged wire in dash behind instrument cluster. My drawing on show tack leads connected to terminal #1 on Tach and going to two connector plug with onlt grey wire coming from tack. Information on tack that is visible without removal indicates tack was calibrated for 12 revolutions. This would suggest that the tack input comes from proximity probe. I will contact REV group tomorrow. In response to Cabbage Hill, cruising was 45 MPH Thanks, Jim Share this post Link to post Share on other sites
desertdeals69 Report post Posted May 14, 2018 Look for the pickup in the housing between the eng and the trans. It maybe 12 pulses per revolutions. Share this post Link to post Share on other sites
abyrd Report post Posted May 14, 2018 DD69, Your are correct, 12 pulsed per revolution. my typing was slower that my thinking. An idea on how to check the output of the proximity probe? Thanks, Jim Share this post Link to post Share on other sites
dickandlois Report post Posted May 14, 2018 Jim, Our Freightliner chassis has a pulse conditioner in the speedometer circuit. The wiring diagram does not show it. The module is powered from the ignition circuit. That might be where the smell came from? Also, the speed sensor on our coach has 2 sensors on the same probe and 4 wires. I have had trans fluid weep from the fluid bath and work its way into the harness connector. Clean it with CRC and reassemble. Some ECMs are set up to use the transmission sensor for the Tachometer and the Speedometer. There is a 2 wire and a 4 wire sensor depending on the setup that was used when the chassis wiring was designed, all related to the Engine and Transmission Year. To count the pulses you could use a Pulse detector prob - to see if it is working. The only real way to get a count is to use an oscilloscope. A frequency counter might work? This is the sensor information DATA sheet for single and double sensor units. Rich. Still looking for the picture I took of the pulse conditioner. Some times there are to many files spread out over applications. LOL Speed sensor link for the Allison AT, MT and HT Series Allison_ Trans_Side-Look-Speed Sensor.pdf Speed sensor link for the Allison 3000 and 4000 Series- There is an upgraded sensor - so the OEM part number will have been superseded. It is a direct interchange for the OEM Sensor. The Motorhome transmissions like the MD 3060 included. Bell Alison Speed sensors_2009_1094.pdf Share this post Link to post Share on other sites
abyrd Report post Posted May 15, 2018 Rick, My issues are with my tachometer not the speedometer. Looks like some us signal from alternator and others a pulse generator. I assume that mine uses a pulse signal because there is a label on the tach housing that it is calibrated for 12 pulses per revolution. I'm trying to data and location of the proximeter that provides signal to tach. I will call REV Group when I arrive at my destination, I just started a 5 week road trip and it failed on the first day out. Thanks Jim Share this post Link to post Share on other sites
manholt Report post Posted May 15, 2018 Jim. When you get your tach working and in sync with your speedometer, do as I have on all my toys. Make a note of optimal (sweet spot) speed/RPM in each gear on regular and economy settings. That way, one or other goes out again, then you have control still. Share this post Link to post Share on other sites
f433921 Report post Posted June 23, 2018 Finally found time to troubleshoot the problem with the tachometer. I had looked at the electrical drawing and with the information that **** provided I determined that the tach signal came directly from the engine ECM and since there was no other issue with the engine running or with transmission shifting I assumed that the ECM RPM signal must be normal and the problem must be the instrument. I checked with HR and they no longer had the instrument cluster which included the tack, oil pressure gauge and volt meter. Further checking with Beebe Instrument and they had been sold to another co and they were unable to support the Beebe line of instruments. I found a used instrument cluster for $65 and it arrived today and I installed it, GUESS WHAT? The tachometer still didn't work. I started chasing the tach signal wire from the tack end didn't have to go very far to find the problem, In the cluster of wiring under the dash there was a single conductor plug that has come disconnected. Plugged it in and all is good. The moral of the story is to look for the simple things and you can save a few bucks. Jim Share this post Link to post Share on other sites
f433921 Report post Posted June 23, 2018 As you can see I lost my user name, picture and profile. This happened when I contact the tech group at FMCA to change my email address. Now I need to find out how to change my user name, anyone have a clue? Jim Share this post Link to post Share on other sites
manholt Report post Posted June 23, 2018 Tech group! Not easy to change user name! Share this post Link to post Share on other sites
wolfe10 Report post Posted June 23, 2018 Contact the IT department at FMCA on Monday. Share this post Link to post Share on other sites
