Komatsu 830E-AC Shop Manual page 221

Relay Board RB6, RB7, RB8, RB9
Relay boards 6, 7,8 and 9 (Figure 3-7) do not contain
circuit breakers or modular cards. Additional circuits
may be added by utilizing a spare relay socket as
described below:
The control circuit for the relays are the "+" and "-"
terminals:
• "+" terminal is for positive voltage.
• "-" terminal is for grounding of the control circuit.
• Either circuit can be switched "open" or "closed" to
control the position of the relay.
The terminals of the switched circuit from the relay
contacts are labeled as follows:
• NC - Normally Closed
• COM - Common
• NO - Normally Open
COM terminal is for the voltage source
(protected by a circuit breaker) coming into
the relay which will supply the electrical
power for the component being controlled.
NC terminal is connected (through the
relay) to the "COM" terminal when the relay
is not energized (when the control circuit
terminals "+" & "-") are not activated).
NO terminal is connected (through the
relay) to the "COM" terminal when the relay
is energized (by the control circuits "+" & "-
") being energized).
Service
To replace a relay:
NOTE: The relays are labelled to identify the
applicable circuits and components Also, refer to the
Fuse Blocks charts at the end of this section.
1. Remove one screw (10, Figure 3-6) holding the
crossbar in place and loosen the other screw.
2. Swing the crossbar away.
3. Gently wiggle and pull outward to remove relay
(11).
4. Line up the tabs and install a new relay.
5. Place the crossbar in its original position and
install screw (10). Tighten both screws.
D03036 10/06
To replace a circuit breaker:
NOTE: Always replace a circuit breaker with one of
the same amperage capacity as the one being
removed.
1. Activate the battery disconnect switches.
2. Unplug all wiring harnesses from the relay
3. Remove four hold down screws (2, Figure 3-6)
4. Remove the nuts on the wire terminal leads on
5. Lift out circuit breaker. Retain flat washers from
6. Install new circuit breaker of the same capacity
7. Install cover plate and all screws removed dur-
8. Carefully install card (5) with screws (6).
9. Install relay board in truck and connect all wiring
To replace a circuit panel card:
NOTE: DO NOT remove the small screws that hold
the cover plate to the circuit panel. Replace circuit
panel as a complete assembly.
1. Place battery disconnect switches in the OFF
2. Remove the two mounting screws (6, Figure 3-
3. Line up the new circuit panel in slots and with
4. Install two mounting screws (6).
24VDC Electrical System Components
board. Remove the four relay board mounting
screws. Remove the relay board from the truck.
(one in each corner) in the circuit breaker cover
plate. Remove two screws (6) and card (5).
the circuit breaker to be replaced. Remove
mounting screws on circuit breaker to be
replaced.
wire terminals.
rating as the one removed. Install one nut and
two flat washers for each wire connection to the
new circuit breaker.
ing disassembly.
harnesses.
position.
6) and carefully remove the circuit panel card
from the relay board.
the socket on the relay board and install care-
fully.
D3-11