E250/350 & F250/350 (7.3L Diesel)
- The electronically-operated tachometer, mounted in the instrument cluster assembly, indicates engine speed in Revolutions Per Minute (RPM). The tachometer receives its signal from the Variable Reluctance Sensor (VRS) mounted in injection pump timing gear cover.
- If tachometer is inoperative or erratic, check fuse. If fuse is blown, check for short circuit. Check for loose wire connections in engine compartment or at instrument cluster. If connections are okay, go to next step.
- Disconnect battery. Remove instrument cluster. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION. Using DVOM, check resistance and voltage at instrument cluster harness connectors.
- Check resistance to ground at pin No. 3 of connector "A". See Fig 1-7. Check resistance between pin No. 9 of connector "A" and corresponding mating connector pin of diesel sensor. Reading should be one ohm or less.
- On vehicles with E4OD transmissions, check resistance between diesel sensor and Electronic Distributorless Ignition System (EDIS) module. Reading should be one ohm or less.
- On all models, connect battery. Turn ignition on. Check voltage at pin No. 13 of connector "A". Voltage should be 12 volts. If readings are not as indicated, problem is not in tachometer. Turn ignition off and disconnect battery. Repair wiring as necessary.
- If resistance and voltage readings are as indicated, check for loose tachometer retention clips at rear of instrument cluster. Check for damaged printed circuit. Check VRS in injection pump timing gear cover. Repair or replace as necessary.
- Remove sensor and check resistance across sensor terminals. If reading is not 2000-3000 ohms, replace sensor.