TACHOMETER READS SLOWLY
-There is a differnce between a tachometer that responds slowly and one that may not be calibrated properly. If the tach does eventually reach the desired RPM, but moves slowly, then it may have a physical resistance issue (internal)
-If the tach looks like its slow but never reaches the desired RPM, it may not be set to the proper cylinder count, which may look like a slow tach. This is common on GM LS installs where the cylinder selection is on #3 (8cyl) and an LS PCM actually outputs a 4 cylinder signal. The tach looks slow but it is actually reading half speed because it is recieveing half of the pulses it is expecting.
If tachometer reads slowly and does not reach desired RPM:
Check for proper cylinder selection:
Gas vehicle cylinder selection
#1 4 cylinder also used on GM LS engines (use 10K-ohm pull up resistor per booklet one side to signal, one side to 12V power)
#2 6 cylinder
#3 8 cylinder
Check the cylinder selection output.
If the tachometer reads properly but is not as responsive as it should be, the pointer or shaft may be hanging up, please contact NVU customer service at 248-850-5481 have the code ACT5515 available