SS300 Service Information (3-2017)
69
TROUBLESHOOTING
SUN-I/O CIRCUIT BOARD TESTING PROCEDURE
STEP
ACTION
VALUE(S)
YES
NO
1
Switched (+)*
•
Key On, circuits loaded (preferred)
•
All electrical components remain con-
nected to wire harness
•
Use an electrical schematic to identify
all switched (+) power supply wires
•
Is there
switched battery voltage (+)
applied to the circuit board?
Applied Volt-
age Must
Be Within 1
Volt of Actual
Battery Volt-
age
Go to Step
#2
Identify Volt-
age Drop
Location
and Repair
or Replace
Necessary
Compo-
nents1
2
Unswitched
(+)*
•
Key On, circuits loaded (preferred)
•
All electrical components remain con-
nected to wire harness
•
Use an electrical schematic to identify
all unswitched (+) power supply wires
•
Is there
unswitched battery voltage
(+)
applied to the circuit board?
Applied Volt-
age Must
Be Within 1
Volt of Actual
Battery Volt-
age
Go to Step
#3
Identify Volt-
age Drop
Location
and Repair
or Replace
Necessary
Compo-
nents1
3
Negative (-)*
•
Key On, circuits loaded (preferred)
•
All electrical components remain con-
nected to wire harness
•
Use an electrical schematic to identify
all negative(-)/ground supply wires
•
Is there
battery negative (-)
applied to
the circuit board?
Applied Volt-
age Must
Be Within 1
Volt of Actual
Battery Volt-
age
Go to Step
#4
Identify Volt-
age Drop
Location
and Repair
or Replace
Necessary
Compo-
nents1
4
Inputs
•
Key On
•
Manually exercise all input devices
and observe status change using a
multimeter
•
Use an electrical schematic to identify
all input circuits
•
Do all inputs function correctly?
Go to Step
#5
Repair or
Replace
Necessary
Input Com-
ponents1
5
Outputs
•
Key On
•
Disconnect battery and circuit board
from wire harness and test output cir-
cuits for open or shorted circuits using
an Ohmmeter.
•
Use an electrical schematic to identify
all output circuits
•
Is there an
open
or
shorted
2 output
circuit causing the trouble symptom?
Repair or
Replace
Necessary
Output Cir-
cuit Compo-
nents1
Replace Cir-
cuit Board.
1 Wire harnesses are components.
2
An open circuit has infinite resistance “O.L.”. A shorted circuit has “0” resistance. Always test through the
entire circuit.
* Switched (+) and Unswitched (+) indicate positive battery voltage applied to the circuit board. Negative (-)
indicates battery negative (ground) as part of the power supply to the circuit board.
