Volt Relay And Diode Boards - Komatsu 830E Shop Manual

24 VOLT RELAY AND DIODE BOARDS

The truck is equipped with 5 relay boards and a
diode board to provide control in many of the 24 volt
electrical system circuits. Some trucks may have a
sixth (Auxiliary) relay board installed.
Each relay board contains 4 relays, all of which are
interchangeable.
Each relay board also contains circuit breakers,
which are also interchangeable between the relay
boards.
DO NOT interchange or replace any circuit
breaker with one of a different capacity than
specified for that circuit. Serious damage or fire
may result if the wrong capacity circuit breaker is
used.
The six relay boards and their primary use are identi-
fied as follows:
• Relay Board 1 . . . . . . . . . . . . . . . . Turn Signal
• Relay Board 2 . . . . . . . . . . . . . . Payload Meter
• Relay Board 3 . . . . . . . . . . . . . . . . .Stop Lights
• Relay Board 4 . . . . . . . . . . . . . . Parking Brake
• Relay Board 5 . . . . . . . . . . . . . . . . Head Lights
• Relay Board 6 . . . . . . . . . . . . . . Auxiliary Panel
The truck is also equipped with a diode board:
• Diode Board 1
Refer to "Table I, Circuit Breakers" for the circuits
each circuit breaker protects.
D3-8
RELAY BOARDS
Description
Each relay board is equipped with four green lights
(9, Figure 3-6) and one red light (7). The four green
lights are labeled K1, K2, K3, or K4. These lights will
be "ON" only when that particular control circuit has
been switched "ON" and the relay coil is being ener-
gized. The light will not turn on if the relay board does
not receive the 24 volt signal to turn "ON" a compo-
nent, or if the relay coil has an "open" circuit.
The red "Breaker Open" light (if "ON") indicates that a
circuit breaker (on that relay board) is in the "OFF"
position. A light on the overhead display panel will
also illuminate, informing the operator that a circuit
breaker is in the "OFF" position. The red breaker
open light will turn "ON" whenever there is a voltage
difference across the two terminals of a circuit
breaker.
If a control switch has been turned "ON" and a green
(K) light is "ON", but that component is not operating,
check the following on the relay board for that circuit:
24VDC Electrical System Components
Check for a circuit breaker that is in the "OFF"
position or a red (breaker open) light is "ON".
If a circuit breaker is "OFF", turn it "ON".
Check operation of component. If it trips
again, check the wiring or component for
defects that could be causing the circuit to be
overloaded.
The contacts inside the relay may not be
closing, preventing an electrical connection.
Swap relays and check again. Replace
defective relays.
Check the wiring and all of the connections
between the relay board and the component
for an "open" circuit.
Defective component. Replace component.
Poor ground at the component. Repair the
ground connection.
D03026