Installation of 7W2743 Speed Switch Assembly{7427} Caterpillar

Introduction

The 7W2743 Speed Switch is used as a direct replacement for the 5N8947 Speed Switch, which has been cancelled.

Application and Installation of 7W2743 Speed Switch Assembly

1. The 7W2743 Speed Switch has an additional oil step function. For direct replacement of the 5N8947 Speed Switch, this third function is not used. For the same functions that are used on the 5N8947 Speed Switch, the 7W2743 Speed Switch has the same terminal numbers.

2. The 7W2743 Speed Switch is compatible with all magnetic pick-ups used with the former 5N8947 Speed Switch. Calibration of the 7W2743 Speed Switch is very similar to the former 5N8947 Speed Switch.

3. The 7W2743 Speed Switch will not shut down the engine, if a loss of the magnetic pick-up signal occurs. It will also not accept the wire harness cover that was mounted on the former 5N8947 Speed Switch.

ASOS = air shut-off solenoid; ESS = engine speed switch; FSOS = fuel shut-off solenoid; SR = slave relay

4. In electrical systems, where the speed switch contacts supply voltage directly to a shut-off solenoid, it is recommended to replace a failed 5N8947 Speed Switch with a 7W2743 Speed Switch and slave relay (1). Package generator sets with a generator-mounted control panel are equipped with a relay, so no additional slave relay is needed.

5. On 12V DC electrical systems, add a 302266 Relay; on 24V to 32V DC electrical systems, add a 9F3099 Relay.

6. The slave relay will be activated by the shut-down fault signal; the relay contacts will energize the solenoid (rather than the speed switch contacts).

7. The slave relay must be mounted with nose (2) and terminals (3) on the bottom.

When a 3N5984 Type 5 Control Panel is used (see Form SENR7968-03, Service Manual for SR4 Generator), the following wiring changes must be made on the 7W2743 Speed Switch.

NOTE: If these changes are not made, the engine oil pressure fault light on the control panel will come on whenever the engine is stopped.

1. Connect the light green wire from terminal 1 of the oil pressure switch (OPS) to terminal 13 (1).

2. Install a jumper wire from terminal 11 (2) to terminal 14 (3).

3. Disconnect the orange wire from terminal 2 of the time delay (TD) relay and from terminal 1 of the oil pressure switch (OPS) and tape both ends securely.

4. Add a #14 wire to the harness from terminal 2 of the time delay (TD) relay to terminal 10 (4) of the 7W2743 Speed Switch.

5. Adjust the oil step speed calibration (see Form SENR3202 Troubleshooting Guide [ETS]) to the same speed as the crank terminate speed setting (usually approximately 500 rpm). All speed switches should be calibrated as outlined in Form SENR3202, when they are installed in any application, except when the oil step feature is not used.