Tachometer, Ametek Electronic 54.21

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1 General Information General Information The Ametek electronic tachometer consists of a dash-mounted gauge, a magnetic sensor mounted on the flywheel housing, and the necessary electrical wiring. An optional model is equipped with a 7-wheel hourmeter that records the total hours of engine operation. The magnetic sensor is mounted through a threaded bore in the flywheel cover. The sensor, when installed and adjusted correctly, is 1/32 inch (1 mm) away from the teeth of the flywheel. See Fig. 1. At the back of the tachometer are 8 DIP switches. See Fig. 2. The tachometer is calibrated by setting the DIP switches on or off to correspond to a specific calibration code. Generally, the number of teeth on the flywheel is used to determine the tachometer calibration code. NOTE: Vehicles equipped with the VIGIL III system and all Cummins and Caterpillar electronic engines do not have magnetic sensors on the flywheels. On these vehicles, the lightbar module or the engine control module provides the signal to the tachometer instead of the magnetic sensor /12/95 f540342b 1. Flywheel Ring Gear 2. Flywheel Housing 3. Magnetic Sensor Jam Nut 4 Tachometer Magnetic Sensor 5 Magnetic Sensor Wiring 2 Fig. 1, Cutaway View of the Tachometer Magnetic Sensor The magnetic sensor is an inductive sensor made with a magnet and a coil of wire. An inductive sensor generates an AC voltage whenever the sensor s magnetic field is moved. When the engine is running, the teeth of the turning flywheel attracts the sensor s magnetic field and the sensor generates a pulsing signal. The tachometer head counts the pulses generated by the magnetic sensor and calculates the engine speed (rpm). For the tachometer to correctly interpret the signal generated by the sensor, the tachometer must be calibrated for the specific number of flywheel teeth on the vehicle. This applies to all flywheel-driven tachometers. 05/06/ OFF f540489a NOTE: Example shows switches set for calibration code : S1=OFF, S2=ON, S3=ON, S4=OFF, S5=OFF, S6=ON, S7=ON, and S8=ON. The black dot shows which end to press in. 1. Tachometer Head 2. DIP Switches Fig. 2, Rear View of the Tachometer Heavy-Duty Trucks Service Manual, Supplement 19, April /1

3 Tachometer Head Removal and Installation Removal 1. Apply the parking brake, shut down the engine, and chock the tires. 2. Remove the screws that attach the tachometer/ speedometer panel to the dash. Pull the panel out to gain access to the back of the tachometer head. See Fig Position the panel, then install and tighten the screws that attach the tachometer/speedometer panel to the dash. 5. Remove the chocks from the tires. 05/05/93 f Fig. 1, Tachometer/Speedometer Panel Removal 3. Unplug the electrical wiring harness connectors from the back of the tachometer head. 4. Remove the Torx -head screws that attach the mounting bracket to the tachometer head, and remove the bracket. 5. Carefully remove the spider from the back of the tachometer. 6. Remove the tachometer head from the speedometer/tachometer panel by pulling the tachometer head out from the front of the panel. Installation 1. Place the tachometer head in the panel. Attach the mounting bracket to the tachometer head, then install and tighten the Torx-head screws. 2. Carefully reattach the spider to the back of the tachometer. 3. Connect the wiring harness connectors to the speedometer and tachometer heads. Heavy-Duty Trucks Service Manual, Supplement 19, April /1

4 Tachometer Head Calibration Calibration 1 Always calibrate a new tachometer head before installing it. 1. See Table 1 to determine the tachometer calibration setting. If the engine application is not listed in the table, determine the number of teeth on the engine flywheel and then consult the tachometer calibration tables for the calibration code. See Specifications, 400 for the tachometer calibration tables. 2. Set the positions of the eight DIP switches to ON or OFF as indicated by the calibration code. See Fig. 1. Using a scribe, an awl, or a straightened paper clip, depress the top of the rocker switch to set it to ON; depress the bottom to set it to OFF. For example, to match the calibration code for an engine with 103 teeth on the flywheel, the number 1 DIP switch is OFF (bottom is depressed), the number 2 switch is ON (top is depressed), number switch 3 is ON, switches 4 and 5 are OFF, switches 6, 7, and 8 are ON, as shown in Fig Install the new calibrated tachometer; see Subject /06/ OFF NOTE: Example shows switches set for calibration code: S1=OFF, S2=ON, S3=ON, S4=OFF, S5=OFF, S6=ON, S7=ON, and S8=ON. The black dot shows which end to press in. 1. Tachometer Head 2. DIP Switches 2 f540489a Fig. 1, Tachometer Head, Rear View Common Tachometer Calibration Codes Engine Flywheel Teeth S1 S2 S3 S4 S5 S6 S7 S8 All with VIGIL III N/A Off Off Off Off On On Off Off Caterpillar 3176 and Off On On On Off Off Off On Caterpillar On Off Off On On On Off Off Cummins without Allison 700 transmission 103 Off On On Off Off On On On Cummins with Allison 700 transmission 118 Off On On On Off On On Off Cummins C Series 138 On Off Off Off On Off On Off Detroit Diesel Series 60 (except ECU driven) 118 Off On On On Off On On Off Detroit Diesel Series 50 or 60 (DDEC II or III; ECU driven) 118 Off Off Off Off On On Off Off Table 1, Common Tachometer Calibration Codes Heavy-Duty Trucks Service Manual, Supplement 19, April /1

5 Magnetic Sensor Replacement and Adjustment Replacement and Adjustment 1. Park the vehicle on a level surface. Apply the parking brakes, and chock the rear wheels. 2. Remove the magnetic sensor. 2.1 Disconnect the harness connector from the magnetic sensor. 2.2 Loosen the magnetic sensor jam nut. Turn the magnetic sensor out of the flywheel housing. See Fig Install the new sensor. See Fig With the jam nut backed off to the outboard end of the new magnetic sensor, turn the sensor by hand into the flywheel housing until it bottoms out on the teeth of the flywheel ring gear. 4. Adjust the new sensor. First, start the engine and allow it to idle. Check that the tachometer is operating at idle; increase engine speed and check that the tachometer increases with throttle activation. If there is no tachometer reading, proceed to troubleshooting section for diagnosis and repair. IMPORTANT: Maintain the correct sensor adjustment, or the tachometer reading will not be correct /12/95 f540342b 1. Flywheel Ring Gear 2. Flywheel Housing 3. Magnetic Sensor Jam Nut 4. Tachometer Magnetic Sensor 5. Magnetic Sensor Wiring Fig. 1, Cutaway View of Magnetic Sensor Installation (rear view) 3.2 Back out the sensor one-half of a turn. See Fig Holding the sensor in place to keep it from turning, tighten the jam nut 18 lbf ft (25 N m). 3.4 Connect the wiring to the sensor and be sure it is locked in place. Heavy-Duty Trucks Service Manual, Supplement 19, April /1

6 Troubleshooting Troubleshooting Procedures NOTE: Do not use the following troubleshooting procedures if the vehicle is equipped with VIGIL III, DDEC II, or DDEC III. Tachometer malfunctions are usually one of two types: the tachometer does not operate at all, or the tachometer readings are inaccurate. Inaccurate Tachometer Incorrect tachometer readings may occur whenever a new tachometer head is installed. Calibrate the tachometer head using the procedure in Subject 110. Inaccurate readings may also occur if the magnetic sensor is not adjusted correctly. Before troubleshooting the system, make sure the magnetic sensor is correctly adjusted. For instructions, see Subject 120. Tachometer Does Not Operate 1. Test the magnetic sensor s output voltage. NOTE: To receive an accurate tachometer reading, a minimum of one volt AC output is needed from the magnetic sensor. 1.1 Disconnect the connector from the magnetic sensor. Inspect both halves of the connector for evidence of corrosion or moisture. Clean and repair the connector if necessary. 1.2 Connect the leads of an AC voltmeter to the pins of the magnetic sensor. 1.3 Run the engine at idle speed, and check the voltage output from the sensor. Then shut down the engine. 1.4 If the voltage is less than one volt, and the sensor was correctly adjusted before troubleshooting the system, the magnetic sensor is damaged; replace it. If the voltage is at least one volt, go to the next step. 2. Check for an open or shorted magnetic sensor by measuring the resistance of the sensor. 2.1 Connect the leads of an ohmmeter to the pins of the magnetic sensor. The resistance should measure 876 ± 88 ohms. 2.2 If the resistance is outside the acceptable range, replace the sensor; see Subject 120. If the resistance is in the acceptable range, go to the next step. 3. Check that the magnetic sensor is not shorted to ground, by measuring the sensor s continuity to ground. 3.1 Connect the positive ohmmeter lead to a pin on the magnetic sensor. Touch the negative ohmmeter lead to a good ground source. The ohmmeter should read infinite ohms. 3.2 If the resistance measured is less than infinite, the magnetic sensor is grounded and must be replaced. If the resistance reading was acceptable, reconnect the magnetic sensor connector and go to the next step. 4. Check the wiring between the magnetic sensor and the tachometer for an open circuit. 4.1 Remove the tachometer/speedometer panel from the dash and disconnect the harness connector from the tachometer; see Subject Check for an open circuit by connecting the ohmmeter leads to the tachometer harness connector terminals 5 and 1 (wiring circuit numbers 162 and 163, respectively). See Fig. 1. The resistance should measure 876 ± 88 ohms. 4.3 If the resistance is above the acceptable range, there is resistance in the wiring between the tachometer and the magnetic sensor. If the resistance is below the acceptable range, there is a short between wire 162 and wire 163. Repair or replace the damaged wiring. Then install the tachometer; see Subject 100. If the measured resistance is in the acceptable range, go to the next step. 5. Check the wiring between the magnetic sensor and the tachometer for a short circuit to ground. 5.1 Disconnect the harness connector from the tachometer head. Connect the positive lead from an ohmmeter to terminal five Heavy-Duty Trucks Service Manual, Supplement 19, April /1

7 54.21 Troubleshooting Tachometer, Ametek Electronic A C B 10A 81C 29A 81C 81C 4 2 F 29A 16 29A G H D E 08/19/97 A. Ignition Fed Circuit Breaker B. Ignition Circuit Breaker Panel C. Relay D. Panel Lamp Rheostat (solid state) E. Tachometer Head F. Magnetic Sensor G. To Fuel Gauge H. To Instrument Panel Lamps f Fig. 1, Tachometer Wiring Schematic (circuit 162), and the negative lead to a good ground source. If the circuit is shorted to ground, a reading of low ohms will be present. If there is no short to ground, the circuit will read infinite ohms. See Fig Connect the positive lead from an ohmmeter to terminal one (circuit 163) at the same connector, and the negative lead to a good ground source. If the circuit is shorted to ground, a reading of low ohms will be present. If there is no short to ground, the circuit will read infinite ohms. 5.3 If the resistance measured was less than infinite ohms in either of the measurements, repair the short to ground in the respective circuit wiring. If the measurement was acceptable go to the next step. 6. Check the ground circuit wiring between the tachometer and ground for an open circuit. 6.1 Connect the positive lead from an ohmmeter to the tachometer harness connector (terminal 3). Connect the negative lead to a good ground source. See Fig. 1. A measurement of 3 ohms or less is acceptable. 6.2 If the resistance measured is more than 3 ohms, repair the wire. If the resistance reading was acceptable, go to the next step. 7. Check for battery voltage at the tachometer connector. 7.1 Connect the positive lead from a voltmeter to terminal four at the tachometer head 300/2 Heavy-Duty Trucks Service Manual, Supplement 19, April 1998

8 Troubleshooting connector. Connect the negative lead to terminal three. Check that the voltmeter is set to DC volts. See Fig Turn the ignition switch on. The voltmeter should read 11 to 13 volts. 7.3 If the voltage is not between 11 and 13 volts, check the voltage at the circuit breaker. Voltage at the circuit breaker should be approximately 11 to 13 volts ± 1 volt. Then check the wiring between the circuit breaker and the tachometer. Repair the damaged wiring and then install the tachometer; see Subject 100. If the voltage is between 11 and 13 volts, the tachometer is malfunctioning and must be replaced. Troubleshooting Tables Problem Less Than One Volt Reading from Magnetic Sensor Problem Less Than One Volt Reading from Magnetic Sensor Possible Cause Remedy The magnetic sensor gap is incorrectly Adjust the magnetic sensor. adjusted. The magnetic sensor is damaged. Replace the magnetic sensor. Problem Tachometer Head Will Not Register Problem Tachometer Head Will Not Register Possible Cause Remedy The magnetic sensor gap is incorrectly Adjust the magnetic sensor. adjusted. The magnetic sensor is damaged. Replace the magnetic sensor. Loose or corroded terminals, broken Replace the damaged wiring component(s) as necessary. terminal connections, broken wires, shorting, grounded, or frayed wires are causing an incomplete circuit. The tachometer head is damaged internally. Replace the tachometer head only after checking all other possible causes. Problem Inaccurate Tachometer Readings Problem Inaccurate Tachometer Readings Possible Cause Remedy The magnetic sensor gap is incorrectly Adjust the magnetic sensor. adjusted. Shorts, or opens are occurring in the Check the resistance of the magnetic sensor. Replace the sensor if necessary. magnetic sensor. The tachometer head is incorrectly Calibrate the tachometer head. calibrated. Erratic readings are resulting from loose Check all the wiring in the tachometer system. Tighten all loose connections. electrical connections, or intermittent short/ open in wiring. Heavy-Duty Trucks Service Manual, Supplement 19, April /3

9 Specifications Ametek Tachometer Calibration Codes FLYWHEEL TEETH S1 S2 S3 S4 S5 S6 S7 S8 85 OFF ON OFF ON OFF ON OFF ON 86 OFF ON OFF ON OFF ON ON OFF 87 OFF ON OFF ON OFF ON ON ON 88 OFF ON OFF ON ON OFF OFF OFF 89 OFF ON OFF ON ON OFF OFF ON 90 OFF ON OFF ON ON OFF ON OFF 91 OFF ON OFF ON ON OFF ON ON 92 OFF ON OFF ON ON ON OFF OFF 93 OFF ON OFF ON ON ON OFF ON 94 OFF ON OFF ON ON ON ON OFF 95 OFF ON OFF ON ON ON ON ON 96 OFF ON ON OFF OFF OFF OFF OFF 97 OFF ON ON OFF OFF OFF OFF ON 98 OFF ON ON OFF OFF OFF ON OFF 99 OFF ON ON OFF OFF OFF ON ON 100 OFF ON ON OFF OFF ON OFF OFF 101 OFF ON ON OFF OFF ON OFF ON 102 OFF ON ON OFF OFF ON ON OFF 103 OFF ON ON OFF OFF ON ON ON 104 OFF ON ON OFF ON OFF OFF OFF 105 OFF ON ON OFF ON OFF OFF ON 106 OFF ON ON OFF ON OFF ON OFF 107 OFF ON ON OFF ON OFF ON ON 108 OFF ON ON OFF ON ON OFF OFF 109 OFF ON ON OFF ON ON OFF ON 110 OFF ON ON OFF ON ON ON OFF 111 OFF ON ON OFF ON ON ON ON 112 OFF ON ON ON OFF OFF OFF OFF 113 OFF ON ON ON OFF OFF OFF ON 114 OFF ON ON ON OFF OFF ON OFF 115 OFF ON ON ON OFF OFF ON ON 116 OFF ON ON ON OFF ON OFF OFF 117 OFF ON ON ON OFF ON OFF ON 118 OFF ON ON ON OFF ON ON OFF 119 OFF ON ON ON OFF ON ON ON 120 OFF ON ON ON ON OFF OFF OFF Heavy-Duty Trucks Service Manual, Supplement 11, March /1

10 54.21 Specifications Tachometer, Ametek Electronic FLYWHEEL TEETH S1 S2 S3 S4 S5 S6 S7 S8 121 OFF ON ON ON ON OFF OFF ON 122 OFF ON ON ON ON OFF ON OFF 123 OFF ON ON ON ON OFF ON ON 124 OFF ON ON ON ON ON OFF OFF 125 OFF ON ON ON ON ON OFF ON 126 OFF ON ON ON ON ON ON OFF 127 OFF ON ON ON ON ON ON ON 128 ON OFF OFF OFF OFF OFF OFF OFF 129 ON OFF OFF OFF OFF OFF OFF ON 130 ON OFF OFF OFF OFF OFF ON OFF 131 ON OFF OFF OFF OFF OFF ON ON 132 ON OFF OFF OFF OFF ON OFF OFF 133 ON OFF OFF OFF OFF ON OFF ON 134 ON OFF OFF OFF OFF ON ON OFF 135 ON OFF OFF OFF OFF ON ON ON 136 ON OFF OFF OFF ON OFF OFF OFF 137 ON OFF OFF OFF ON OFF OFF ON 138 ON OFF OFF OFF ON OFF ON OFF 139 ON OFF OFF OFF ON OFF ON ON 140 ON OFF OFF OFF ON ON OFF OFF 141 ON OFF OFF OFF ON ON OFF ON 142 ON OFF OFF OFF ON ON ON OFF 143 ON OFF OFF OFF ON ON ON ON 144 ON OFF OFF ON OFF OFF OFF OFF 145 ON OFF OFF ON OFF OFF OFF ON 146 ON OFF OFF ON OFF OFF ON OFF 147 ON OFF OFF ON OFF OFF ON ON 148 ON OFF OFF ON OFF ON OFF OFF 149 ON OFF OFF ON OFF ON OFF ON 150 ON OFF OFF ON OFF ON ON OFF 151 ON OFF OFF ON OFF ON ON ON 152 ON OFF OFF ON ON OFF OFF OFF 153 ON OFF OFF ON ON OFF OFF ON 154 ON OFF OFF ON ON OFF ON OFF 155 ON OFF OFF ON ON OFF ON ON 156 ON OFF OFF ON ON ON OFF OFF 400/2 Heavy-Duty Trucks Service Manual, Supplement 11, March 1996

11 Specifications FLYWHEEL TEETH S1 S2 S3 S4 S5 S6 S7 S8 157 ON OFF OFF ON ON ON OFF ON 158 ON OFF OFF ON ON ON ON OFF 159 ON OFF OFF ON ON ON ON ON 160 ON OFF ON OFF OFF OFF OFF OFF 161 ON OFF ON OFF OFF OFF OFF ON 162 ON OFF ON OFF OFF OFF ON OFF 163 ON OFF ON OFF OFF OFF ON ON 164 ON OFF ON OFF OFF ON OFF OFF 165 ON OFF ON OFF OFF ON OFF ON 166 ON OFF ON OFF OFF ON ON OFF 167 ON OFF ON OFF OFF ON ON ON 168 ON OFF ON OFF ON OFF OFF OFF 169 ON OFF ON OFF ON OFF OFF ON 170 ON OFF ON OFF ON OFF ON OFF Table 1, Ametek Tachometer Calibration Codes Heavy-Duty Trucks Service Manual, Supplement 11, March /3

Stewart-Warner Electronic Tachometer 54.07

Stewart-Warner Electronic Tachometer 54.07 General Description General Description Engine speeds are shown in revolutions-per-minute (rpm) by the electronic tachometer (Fig. 1). The tachometer is used as a guide for shifting, and to keep the engine