Guest |649| Posted October 20, 2011 Report Share Posted October 20, 2011 I've searched and read, but haven't found the answer to an issue I've had for a while. My stock tacho doesn't work properly, however my Autometer shift light with integrated digital tacho does. Both the stock tacho and Autometer shift light are connected to the same Aux output. The 'KeyON Sweep' feature is ON, and it works as it should, sweeping the stock tacho needle and Autometer shift light/digital tacho when the key is switched to the ON position. When the engine is running, the stock tacho does not work at all (the needle does not move from 0) but the Autometer shift light/tacho does work. The car is a 1996 Mazda. ECU is a Vi-PEC V88. ...and here's the very strange part. The stock tacho started working all on its own the other day. Later that day I realized that the alternator wasn't putting out a charge. I replaced the alternator, and now the stock tacho is back to not working while the engine is running. I've disconnected the alternator a few times and get the same results: With car running & alternator working (~14.3 volts), the stock tacho does not work. With car running and alternator disconnected (~12.5 volts), everything works, including the stock tacho. It seems to me that the stock tacho cannot function when the system voltage is above 12.5 volts. Does that make any sense? I would appreciate help understanding: A. Why B. How do I 'fix' it? Thanks in advance, Will Quote Link to comment Share on other sites More sharing options...
Simon Posted October 21, 2011 Report Share Posted October 21, 2011 How does the tacho respond with out the autometer gear connected? It might be the pull up is not enough to allow two devices. I which case we can use an external pullup. Quote Link to comment Share on other sites More sharing options...
Guest |649| Posted October 22, 2011 Report Share Posted October 22, 2011 Hello Simon, Thanks so much for the help! I hadn't even considered that. I actually have 3 devices on the tacho output: stock tachometer, Autometer tachometer, and output to my data acquisition box. I removed the wire to my data acquisition box and the stock tachometer sprung to life! That solves my problem perfectly. Since I recently connected my Vi-PEC V88 to my Race-Technology DL-1 logger via serial communication, I no longer need that particular wired connection anyway. The stock tacho and Autometer shift light are now working in perfect harmony - thanks again! Cheers, Will Quote Link to comment Share on other sites More sharing options...
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