Tacho erratic function
Posted: Wed Feb 24, 2016 4:30 pm
I have a Harris G80 that displays erratic tacho readout. It is steady up to around 2500 rpm and then swings to max rpm.
I suspected this was noise interference on the signal line so rerouted the cable on the opposite side to the HT. No change.
I then disconnected the output from the regulator and hey presto the taco behaves normally, great so the noise is from the regulator or alternator. I then fitted a voltage regulator chip(LM2940) in the 12volt feed to the tacho which drops the voltage from 14.5v to 12 exactly and is supposed to smooth out spikes, but it makes no difference. This machine is not running with the original voltage regulator, a CEV 6704, apparently unobtainable, I have tried. The CEV is a 6wire unit and the one being used is a 4 wire from the club spares.
Does anybody have any ideas if this might be the regulator? Or maybe the alternator is very noisy, the voltage outputs are normal........Help
I suspected this was noise interference on the signal line so rerouted the cable on the opposite side to the HT. No change.
I then disconnected the output from the regulator and hey presto the taco behaves normally, great so the noise is from the regulator or alternator. I then fitted a voltage regulator chip(LM2940) in the 12volt feed to the tacho which drops the voltage from 14.5v to 12 exactly and is supposed to smooth out spikes, but it makes no difference. This machine is not running with the original voltage regulator, a CEV 6704, apparently unobtainable, I have tried. The CEV is a 6wire unit and the one being used is a 4 wire from the club spares.
Does anybody have any ideas if this might be the regulator? Or maybe the alternator is very noisy, the voltage outputs are normal........Help