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SECTION 4.4
DIAGNOSTIC TESTS
Figure 5. The Starter Contactor Relay
PROCEDURE:
1 Set a VOM to measure DC voltage.
2. Connect the positive (+) meter test lead to the Wire 13
connector. Connect the negative (-) meter test lead to a
clean frame ground. Battery voltage should be measured.
3. Connect the positive (+) meter test lead to the Wire 16
connector. Connect the negative (-) meter test lead to a
clean frame ground.
4. Set the AUTO-OFF-MANUAL switch to MANUAL.
Observe the meter reading. Battery voltage should
measured. If battery voltage is NOT measured, proceed
to Step 5.
5. Set the VOM to it’s “R x 1” scale to measure ohms.
6. Connect one test lead to the Wire 0 connector. Connect
the other test lead to a clean frame ground.
CONTINUITY should be measured.
RESULTS:
1 If battery voltage is NOT measured in Step 2, repair or
replace wiring between starter contactor relay and fuse
(F2).
2. If battery voltage is NOT measured in Step 4 and
CONTINUITY is measured in Step 6, replace the starter
contactor relay.
3. If battery voltage is measured in Step 4. proceed to
Test 49.
TEST
49-
TEST
STARTER
CONTACTOR
DISCUSSION:
The starter contactor (SC) must energize and its heavy
duty contacts must close or the engine will not crank.
This test will determine if the starter contactor is in
working order.
PROCEDURE:
Carefully inspect the starter motor cable that runs from
the battery to the starter motor. Cable connections must
be clean and tight. If connections are dirty or corroded,
remove the cable and clean cable terminals and
terminal studs. Replace any cable that is defective or
badly corroded.
Use a DC voltmeter (or a VOM) to perform this test.
Test the starter contactor as follows:
1. Connect the positive (+) meter test lead to the starter
contactor stud (to which the red battery cable connects).
Connect the common (-) meter test lead to a clean frame
ground. Battery voltage (12 volts DC) should be indicated.
2. Now, connect the positive (+) meter test lead to the
starter contactor stud to which the starter motor cable
attaches (see Figure 6 or 7). Connect the common (-)
test lead to frame ground.
a.No voltage should be indicated initially.
b.Set the AUTO-OFF-MANUAL switch to MANUAL.
The meter should now indicate battery voltage
as the starter contactor energizes.
Figure 6. The Starter Contactor (Single Cylinder Units)
DC CONTROL
PART 4
Page 4.4-5