Sakai SW880-1, Shop Manual

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11-009
TROUBLESHOOTING
2-1-3. Inspection of electrical system
Operate the applicable switches and turn the relays ON and OFF. Ultimately, if the solenoid valve operates (makes
a sound) and the pump runs, the electrical system is OK.
If there is a failure (fault), narrow the range of the inspection to the six broad steps described below.
1) Ground inspection
Check for disconnected or loose ground. If rust or corrosion is present (which can cause faulty contact),
remove the rust.
2) Fuse inspection
2-1) Check for blown fuses, disconnections and corrosion. (A fatigue open circuit cannot be identified visually.
Use a tester for checking.)
2-2) If a fuse is blown
Check whether a pump or valve (that is supposed to be protected by a blown fuse) burned, and whether
there is a burning odor.
Especially if the pump and valve are not burned, check the harness for signs of burning. If it is burned,
replace it.
If a fuse is blown and a relay along the pathway has failed, replace it. And if there is a timer, replace the
timer, too. If a switch visually appears to be unsatisfactory (burned, melted, etc.) even though it operates,
replace it.
Simply replacing a fuse may not eliminate the true cause of a problem, and over current may flow again.
Also, if over current secondarily causes an electrical path to fail (such as a wiring meltdown inside a
solenoid valve), current will not flow. Thus, a fuse may not be blown out, but it also will not operate. If you
do not know the location of burning or of an odor, investigate as described follows.
2-3) How to find cause of failure when fuse blown is reproduced
①
Turn the starter switch OFF, and remove the connector from the load (valve, pump).
②
Referring to the circuit diagram, remove electrical parts that are connected to the circuit, such as relays,
timers and diodes.
③
Turn the starter switch ON, and see whether the conditions can be reproduced (fuse is blown).
④
If a fuse is blown, a part such as a relay may have caused a short between the previous harness and
ground (vehicle body). (Replace the harness.) If the conditions are not reproduced, check for signs of
burning (odor) on the removed electrical parts.
⑤
If there is no problem, turn the starter switch OFF and reattach the parts.
⑥
Turn the starter switch ON and try again.
⑦
If a fuse is blown with this action, the problem was caused by a short between the harness and ground
(vehicle body) that followed the attached electrical part. (Replace the harness.)
⑧
If the conditions are not reproduced, turn the starter switch OFF, and connect the loads (valve and
pump) one at a time. Turn the starter switch ON and try again to see whether the fuse blown is
reproduced.
⑨
If the fuse blown is reproduced, whatever was added at that time (including a harness added
electrically) will be the cause of the failure.
Even if the fuse is not blown and the valve or pump is not burned, the valve or pump may be damaged
electrically and may not operate. There may simply be a disconnection in the interior or an abnormal
heat-up.
Even if the fuse is not blown, abnormal heat-up (hot enough to cause burns if touched) may occur if a
relay, timer, diode or other semiconductor fails.
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