881364A04 Mercury HARNESS ASSEMBLY

Table 1
Desired Speed Source by Throttle Number    
Throttle Number    Name    Remote/Local    
Throttle 1     Propulsion     Remote    
Throttle 2     Generator     Remote    
Throttle 3     Local     Local    The desired speed source for each engine is selected using a local/remote throttle select input and a throttle select (generator/propulsion or gen/prop) input. Table 2 describes this relationship.
Table 2
Desired Speed Source by Switch States    
Local/Remote    Gen/Prop    Desired Speed Source    
Active     Active     Local (Speed Pot)    
Inactive Local (Speed Pot)    
Inactive     Active     Generator    
Inactive Propulsion    
Illustration 1 g03282336
Desired speed source wiring with a switchBoth the local/remote throttle select input and the throttle select (gen/prop) input follow the same logic and wiring scheme. The input is considered to be active when a path to ground is provided. One way to accomplish this is with a switch as shown in Illustration 1.
Illustration 2 g03282337
Desired speed source wiring with a relay. (only the inputs for one engine are shown)The ground must be the same as the MCM ground (not all grounds are equal), and therefore a ground source for each switch is provided on the terminal block. Typical wiring for these inputs is shown in Illustration 2 (only the inputs for one engine are shown).Note: Relays not supplied by CaterpillarIndication
Messaging
Each engine has a remote/local input as well as a throttle select (gen/prop) input. As such, each engine has a selected Desired Speed Source, also known as the Desired Throttle Input. The messages indicating the selected Desired Speed Source are communicated via CDL at the following addresses:
Engine 1 Desired Throttle Input: $D1 $0024
Engine 2 Desired Throttle Input: $D1 $0025In some cases, the selected Desired Speed Source is not the same as the actual Desired Speed Source that is currently being used to control the engine. This may be due to such things as Desired Speed Source Change Inhibits or conditions related to coupling. To give an indication of the actual Desired Speed Source, also known as the Actual Throttle Input, each engine has a message at the following addresses:
Engine 1 Actual Throttle Input: $D1 $0026
Engine 2 Actual Throttle Input: $D1 $0027Relays
Illustration 3 g03282356
Dry Contact Relays for Local/Remote StatusA set of dry contacts is provided on the panel to indicate the local or remote status of each engine. The dry contacts are shown in Illustration 3 with the corresponding terminal block labels.Failure Modes
Tables 3, 4, 5, and 6 describe what happens during each of the Desired Engine Speed controls failures. Refer to the "CDL Diagnostics and Codes" section of the, "Diagnostic Codes" chapter of this manual for error codes corresponding to these failures.
Table 3
Speed Source Fail Mode (Coupled, Engine 1 Master)    
   If Source 1 Fails, Is Source 1 in Control?    
Source 1    Yes (diagnostic and )    No    
Generator     use Propulsion 1 for control     diagnostic only    
Propulsion 1     use Propulsion 2 for control     diagnostic only    
Propulsion 2     engines go to low idle     diagnostic only    
Local 1 (1)     Use Local 2     diagnostic only    
Local 2 (1)     engines go to low idle     diagnostic only    
( 1 ) Unlike typical Cat PWM input diagnostics, the Local Speed Pot valid range is a PWM signal between 2-98 percent.
Table 4
Speed Source Fail Mode (Coupled, Engine 2 Master)    
   If Source 1 Fails, Is Source 1 in Control?    
Source 1    Yes (diagnostic and )    No    
Generator     use Propulsion 2 for control     diagnostic only    
Propulsion 2     use Propulsion 1 for control     diagnostic only    
Propulsion 1     engines go to low idle     diagnostic only    
Local 2 (1)     Use Local 1     diagnostic only    
Local 1 (1)     engines go to low idle