Usage:
3606, 3608, 3612, 3616 Industrial Engines
Description of Change: A relay has been added to the pyrometer circuit on the 7C9064 Instrument Panel used on the above engines. This protects the internal parts of the pyrometer switch from voltage surges. The switch for the exhaust stack temperature alarm is activated through the battery negative terminal of the pyrometer through the switch, and energizes the new 9Y2921 Relay.
Adaptable To: The 9Y2921 Relay can be added to the 7C9064 Instrument Panel on earlier engines as shown. The upper part of the illustration shows the physical appearance of the modifications to the existing pyrometer wiring with the relay added. The lower part of the illustration shows the same two parts schematically connected together.
Wiring connections for the new relay.
The procedure to connect the additional relay follows.
1. Remove wire from pyrometer switch (-) and connect to relay terminal 87.
2. Remove jumper wire between pyrometer VDC (+) and switch (+), and connect between pyrometer VDC (-) and switch (-).
3. Install a new wire between pyrometer VDC (+) and relay terminal 30.
4. Install a new wire between pyrometer VDC (+) and relay terminal 85.
5. Install a new wire between pyrometer switch (+) and relay terminal 86.