Calibration Test

Connect a calibrated, reliable tach-dwell meter to ignition system. Compare tach-dwell meter readings with vehicle tachometer readings. If vehicle tachometer readings are not within range of allowable variation, replace vehicle tachometer. See TACHOMETER ALLOWABLE VARIATION  .

1. If tachometer needle deflects beyond maximum point, will not return to zero, or will not exceed a certain point, replace tachometer. For all other conditions, check fuse. If fuse is okay, check instrument cluster power and ground circuits (if temperature gauge operates, instrument cluster power and ground circuits are okay).
2. If power and ground circuits are okay, check continuity between ignition coil negative (-) terminal and instrument cluster. If continuity exists, replace tachometer.