MTD 700 Series Professional Shop Manual page 144

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Series 700 Lawn Tractor
6. Voltage drop on a good circuit should be less than
0.1 volts. A voltage drop reading on the meter of
greater than 0.2 volts indicates a fairly substantial
problem that demands attention.
• As an example, if the mower had a slow-turning
starter, the ground-side voltage drop measured
below 0.1 volts, and there was not a parasitic
load on the engine (e.g. PTO clutch that is not
fully disengaged), it would be logical for the
technician to check voltage drop to the starter.
See Figure 7.58.
• With the starter motor engaged, the voltage
drop reading here is nearly 0.6 volts, indicating
a serious problem in the heavy-gauge circuit
between the starter and the battery.
• Checking voltage-drop at various points along the circuit can help pin-point the problem.
• Check voltage-drop at the output lug on the starter solenoid:
• If there is a significant difference, the problem lies between the lug on the solenoid and the lug on the
starter.
• If there is little change, the problem lies further up-stream.
• Check voltage drop at the input lug on the solenoid. If there is significant difference between the reading
here and the reading at the output lug (greater than 0.10 volt), then the contacts inside the solenoid may
be burned. If there is little change, the problem lies further up-stream, between the battery and the sole-
noid.
• Results may be cross-checked by testing voltage drop across the two posts of the starter solenoid while
cranking the starter motor.
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Figure 7.58