LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 1998 >> C3500 HD 6.5 F, Automatic >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Testing & Diagnosis >> Tachometer Test >> Tachometer Inaccurate

Tachometer Inaccurate

  1. Start and operate engine at 1000 RPM without racing engine. Record tachometer. Disconnect ignition coil connector (gasoline) or generator connector (diesel). Connect a hand-held tachometer to ignition coil (gasoline) or generator (diesel) tachometer output (White wire). Record RPM.
  2. If RPM indicated by hand-held tachometer is within 250 RPM of vehicle tachometer, tachometer accuracy is acceptable. If RPM indicated by hand-held tachometer is not within 250 RPM of vehicle tachometer, and no other driveability or emission problems are present, replace instrument cluster.
NOTE: Before performing following test, ensure Distributor Ignition (DI) system is operating correctly. See BASIC TESTING article in ENGINE PERFORMANCE section.
scientia non olet · About LEMON Manuals