Other Electrical Fault Tracing

JA. Checking Leads And Connections

Many faults in electrical systems are due to faults in leads and connections. These faults are usually due to interference from other electrical systems, mechanical or chemical effects.

JA1 Checking Connections Visually

Whenever a connector's opened for taking readings or checking connections it should be inspected visually.

Checks:
Look for oxidation which can affect contact in the connections. Make sure connection tabs are intact and that the copper conductor is properly connected to the tab.





JA2 Open-Circuits

Open-circuits show up when something stops working. Chafed and worn cables as well as connections which have worked loose are common causes of faults.




Checks:
Disconnect connectors at both ends of cable. Using an ohmmeter, measure between ends of cable. Ohmmeter should read approximately 0 ohm if there is no open-circuit in the cable

Checking for intermittent open-circuits:
Check lead visually as per JA1. Gently shake leads and pull lightly on connections during the course of taking measurements to find faults.


JA3 Short-Circuit To Ground

A short-circuit between a supply cable and ground is often discovered when the power is turned on to a component and the fuse blows or when something stops working.





Checks:
Operate all switches and sensors in the circuit and see if the fuse blows. Disconnect connectors from components in the circuit so they do not affect readings. Using an ohmmeter, measure between the lead and ground. Ohmmeter should read infinite resistance when no components are connected up.





Checking for intermittent short-circuit to ground:
Check lead visually as per JA1. Gently shake leads and pull lightly on connections during the course of taking measurements to find where lead is damaged.

JA4 Short-Circuit To Supply

A short-circuit between a supply cable and ground is often discovered when the power is turned on to a component and the fuse blows or when something stops working.





Checks:
Using a voltmeter, take readings at different points in the circuit while at the same time operating switches and sensors. The voltmeter reading depends on the circuit being tested and the positions of switches and sensors. Use the wiring diagram to find the correct voltage for the circuit.





Using an ohmmeter, take readings between suspect leads to see if there is a short-circuit between them. The ohmmeter should indicate infinite resistance when taking a reading between cables which are not connected to each other in circuit.


Checking for intermittent short-circuit to supply:
Check lead visually as per JA1. Gently shake leads and pull lightly on connections during the course of taking measurements to find where lead is damaged.


JA5 Loose Contacts (Connections)







Loose contacts in connections are caused by oxidation on pins and contacts or leads not being connected properly. A loose contact has the same effect as an intermittent open-circuit in a lead.

Checks:
Check connections visually as per JA1. Gently shake leads and pull lightly on connections during the course of taking measurements to find where lead is damaged.



JA6 Contact Resistance Oxidation

Resistance in contacts, cables and connections should normally be 0 ohm. But there is always some resistance due to oxidation on connections and wear. If the resistance is too great it will effect system function. How great the resistance can be without interfering with system function will vary depending on how great the circuit loading. A typical value would be a few ohm.


Checks:
Check connections visually as per JA1.

Cleaning female contacts and male tabs

NOTE: Do not use rust solvent sprays or grease on any of the Lambda Sonde oxygen sensor connectors.


Disconnect the battery negative terminal cable.
Spray anti-rust spray 1161034-2 on the two open connector halves.
Blow clean with compressed air.





NOTE: Do not fill the protective cover with grease.

Greasing female contacts

Press grease 1161417-9 in to the female contacts directly from the tube. Check the cavities are filled in all the contact sockets.




Use a separate male pin terminal to test that the female contacts give a good contact and that the terminal stays in place if the male pin terminal is pulled gently.