Other Fault-Tracing
Checking Leads And Connections
Many faults in electrical systems are due to faults in leads and connections. These faults are mainly due to interference from other electrical systems, mechanical or chemical effects.
WA1 Check Connections Visually
In all tests and checks which involve taking connectors apart, check connections visually.
Checks:
Look for signs of oxidation which may affect contact in connections.
Check that connector pins are intact and that copper wires are properly connected to pins.
WA2 Resistance In Leads, Contacts And Connections
Resistance in leads, contacts and connections should be 0 ohm. However, there is always some resistance due to poorly connected wires, oxidation on connections and wear. If resistance becomes too great, something will stop working properly. How high resistance can be without causing problems depends on how high the load is in the circuit. A guideline is a few ohms.
Check Intermittent Faults
Check connections visually as per WA1.
Shake leads and pull on connections gently during testing to find where the lead is damaged.
Always check control module connector for bent or damaged pins or sleeves.
Test Using An Ohmmeter:
Ignition off.
Undo connectors at both ends of lead.
Connect an ohmmeter between ends of lead.
Before starting test, check that instrument is reading 0 ohm when test leads are held together. Shake lead gently while watching the meter.
Ohmmeter should not read more than a few ohms in a circuit with acceptable resistance in contacts and connections.
WA3 Open-Circuit In Circuit
An open-circuit shows up when something stops working. Rubbed and worn leads and connections which have come loose are common sources of fault.
Check:
Ignition off.
Undo connectors at both ends of lead.
Connect an ohmmeter between ends of lead.
Ohmmeter should read approx. 0 ohm if there is no open-circuit in a lead.
Checking for intermittent open-circuit:
Check lead visually as per WA1.
Shake lead gently and pull gently on connections while testing to find where lead is damaged.
WA4 Short-Circuit To Ground
A short-circuit between a supply lead in a circuit and ground often shows up when the fuse blows when power is applied to the lead or when something does not work.
Check:
Ignition off.
Remove fuse which blew.
Disconnect components in circuit.
Connect an ohmmeter between ground and the lead to be tested.
If test equipment reads infinite resistance when no components are in circuit, there is no short-circuit.
If test equipment shows low resistance, approx. 0 ohm, lead is short-circuited to ground.
Checking intermittent short-circuit to ground:
Check lead visually as per WA1.
Shake lead and pull connections gently while testing to find where lead is damaged.
WA5 Short-Circuit To Supply
Short-circuit between a lead and supply often causes the fuse to blow when power is supplied to the lead. The fault. usually shows up when something does not work.
Check:
Ignition off.
Connect a voltmeter at different points in the circuit while operating switches and sensor. Which supply voltmeter should read depends on which circuit is being tested and position of switches and sensors. Use wiring diagram to find right supply in the circuit. Connect an ohmmeter between suspect leads to find short-circuits between them.
Ohmmeter should read infinite resistance when testing between leads not connected to one another in circuit.
Checking intermittent short-circuit to ground:
Check lead visually as per WA1.
Shake lead and pull on connections gently while testing to find where lead is damaged.
WA6 Cleaning Female Contacts And Male Pins
Ignition off.
Spray anti-rust spray on the disconnected connectors.
Blow clean with compressed air.
NOTE: Do not fill cavity with grease.
Greasing Female Contacts
Press grease 1161417-9 into female contacts directly from tube.
Check that space is filled in all connector sleeves.
Using a loose male pin, check that female contacts connect properly and that the male pin does not come away when pulled gently.