Trouble getting stock tach to read correctly
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From: St Simons Isl, GA
Trouble getting stock tach to read correctly Car is a '75 Corvette, and all the gauges are stock. The tach in a '75 is an electronic tach, so I should have been good to go by wiring in the wire from the PCM (PSI conversion harness) to my stock plug on the back of the tach, and then changing the high and low resolution on the tach output in HPTuners to 3 instead of 6...
The tach reads correctly at idle and up until about 2000rpms...then it takes off and is reading 500-600rpms too high by about 2300rpm or so (I'm comparing the reading on the tach to the reading on the scanner in HPTuners). The reading is off more and more the higher in the rpm range I rev the motor.
So from idle to 2000...correct.
Reading 2300 on HPT....almost 3000 on the gauge.
And so on...
Any ideas here? I just put a new circuit board in the tach, so that should be OK. I'm about ready to say screw it and put in a set of aftermarket gauges and be done with it, but I have everything else reading correctly except the speedo....
TIA.
The tach reads correctly at idle and up until about 2000rpms...then it takes off and is reading 500-600rpms too high by about 2300rpm or so (I'm comparing the reading on the tach to the reading on the scanner in HPTuners). The reading is off more and more the higher in the rpm range I rev the motor.
So from idle to 2000...correct.
Reading 2300 on HPT....almost 3000 on the gauge.
And so on...
Any ideas here? I just put a new circuit board in the tach, so that should be OK. I'm about ready to say screw it and put in a set of aftermarket gauges and be done with it, but I have everything else reading correctly except the speedo....
TIA.
