Chery A1 2009 Service Manual page 19

Voltage Drop Test
Voltage drop tests are often used to find components or circuits which have excessive resistance. A voltage drop in
a circuit is caused by a resistance in the circuit during operation.
• Check the circuit using a Digital Multimeter (DMM).
• When measuring resistance with a DMM, remember that contact by a single strand of wire will give a reading
of 0 ohms. This would indicate a good circuit. When the circuit operates, this single strand of wire is not able
to carry the current. The single strand will have a high resistance to the current. This will be indicated as a
slight voltage drop.
• Unwanted resistance can be caused by the following:
− Undersized wiring (single strand example)
− Corrosion on switch contacts
− Loose wire connections or splices
Precautions For Handling Control Modules and Electrical Components
• Never reverse polarity of battery terminals.
• Only install components specified for the vehicle.
• Before replacing the control module, check the input and output and functions of the components.
• When disconnecting components:
− Do not apply excessive force when disconnecting a connector.
− If a connector is installed by tightening bolts, loosen mounting bolt, then remove it by hand.
• When connecting components:
− Before installing a connector, make sure the terminal is not bent or damaged, and then correctly connect it.
− When installing a connector by tightening bolts, tighten the mounting bolt until the painted area of the con-
nector becomes even with the surface.
• Do not apply excessive shock to the control module by dropping or hitting it.
• Be careful to prevent condensation in the control module due to rapid temperature changes and do not let
water or rain get on it. If water is found in the control unit, dry it fully and then install it in the vehicle.
• Be careful not to let oil get on the control module connector.
• Avoid cleaning the control module with volatile oil.
• When using a DMM, be careful not to let the test probes touch each other causing a short circuit. Prevent the
power transistor in the control module from being
shorted to damaging battery voltage.
• When checking input and output signals of the con-
trol module, use the specified test adapter (if
applicable).
18
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DIAGNOSING ELECTRICAL FAILURES
LTSMD030028
Chery Automobile Co., Ltd.