Normal close INC) type
Deenergized state
Energized state
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WIRING HARNESS - Troubleshooting 8-17
When a normal close type relay as illustrated here is checked,
there should be continuity between terminals (1) and (2) and
between terminals 3 and 4 when the relay is deenergized,
and the continuity should be lost between terminals 3 and 4
when the battery voltage is applied to the terminals 1 and 2. A
relay can be checked in this manner and it cannot be deter-
mine if a relay is okay or faulty by checking its state only when
it is deenergized (or energized).
Current -flows Current does not flow
1680234
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1680235
State of fuse blown due to overcurrent
1660237
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State of fuse blown due to thermal fatigue
CHECKING FUSES
A blade type fuse has test taps provided to allow checking of
the fuse itself without removing it from the fuse block. The
fuse is okay if the test light comes on when its one lead is
connected to the test taps (one at a time) and the other lead is
grounded.
(Change the ignition switch position adequately so that the
fuse circuit beomes live.)
CAUTIONS IN EVENT OF BLOWN FUSE
When a fuse is blown, there are two probable causes as follows
: One is that it is blown due to flow of current exceeding its rating.
The other is that it is blown due to repeated on/off current flowing
through it. Which of the two causes is responsible can be easily
determined by visual check as described below.
(1) Fuse blown due to current exceeding rating
The illustration shows the state of a fuse blown due to this
cause. In this case, do not replace the fuse with a new one
hastily since a current heavy enough to blow the fuse has
flowed through it. First, check the circuit for shorting and
check for abnormal electric parts. Only after the correction of
such shorting or parts, fuse of the same capacity should be
used as a replacement. Never use a fuse of lager capacity than
the one that has blown. If such a fuse is used, electric parts or
wirings could be damaged before the fuse blows in the event
an overcurrent occurs again.
(2) Fuse blown due to repeated current on/off
The illustration shows the state of a fuse blown due to re-
peated current on/off. Normally, this type of problem occurs
after fairly long period of use and hence is less frequent than
the above type. In this case, you may simply replace with a
new fuse of the same capacity.
