How to Diagnose Vehicle Circuit Failure by Sigmaprobe Tester

How to Diagnose Vehicle Circuit Failure by Sigmaprobe Tester

Open circuit refers to the mechanical disconnection of the current channel. In a series circuit, if the current is interrupted, the circuit stops working. In a parallel circuit, if one branch is disconnected, this branch will stop running and other branches will work as usual. Continuity of the circuit can be tested by using a Sigmaprobe tester. In an open circuit, because there is not a complete current in and out of the power supply circuit, the current cannot flow in the circuit.

sigmaprobe tester

There are two possibilities for circuit breaker:

One is a continuous open circuit, the other is an intermittent open circuit. One of the most troublesome is the intermittent open circuit. An intermittent open circuit is often the conductor in the insulation layer break, but the disconnection in the conductor still keeps in contact when parking. Because of the vibration of the vehicle during driving, it will produce an intermittent open circuit. To find such an open circuit, you can swing the suspected wire with your hand to see if there is an intermittent open circuit or not.

Followings are some examples of open circuits:

1) The wire is disconnected or the connector is loose.
2) The fuse is burnt out or the circuit breaker is tripped.
3) Internal open circuit of components such as switch, bulb, etc.
4) The resistance is very high and often shows the same symptoms as an open circuit.

Accidental damage or vibration often causes wire breaking and open-circuit.

It's usually easy to observe the wire damage causes open-circuit; the open circuit caused by vibration is often difficult to find because the insulation layer of the conductor is still intact. It can only be searched with professional instruments like Sigmaprobe tester, this kind of open circuit is likely to be intermittent. Loose joints can also be caused by vibration or improper assembly.

Both fuse burnout and circuit breaker tripped all appear as open circuits.

Circuit overload can cause an open circuit. At this time, in order to protect the circuit and components, the safety device will actively cut off the circuit. The quality of the insurance can be determined by observing whether it is burnt out or not. This kind of open circuit is often the symptom of a short circuit or overload in the circuit.

The Normal wear and tear of some can cause internal open circuit (burnout) of the components, (such as bulb).

Normal wear and tear also occur on other parts after long-term use, such as switches and motors. However, if such parts are worn out in a short period of time, you should look for the causes of premature damage to these parts.
High resistance is like an open circuit because high resistance prevents current from flowing through the circuit. Corrosion of terminals and ground connections often causes high resistance.

Diagnosis of vehicle open circuit

First, find the obvious cause of wire or insulator breakage, such as corrosion.
In a simple series circuit, the open circuit will prevent the current flow, causing all loads in the circuit not to work, such as the motor does not turn, the lamp does not light, etc.

Diagnosis of vehicle open circuit

Before the breaking point, there is still voltage between the circuit and the ground wire, and on the other side of the breaking point, the voltage does not exist. In a simple parallel circuit, the open circuit will prevent the current flow, and the voltage of all points connect to the power supply is the same as that of the power supply.

In the composite circuits, the effect of the open circuit on current and voltage is different. In the composite circuit, the current may choose other branches. Different circuits will have different abnormal phenomena, so that you cannot directly understand the fault. Checking the circuit diagram will help to explain these anomalies.

Diagnosis of vehicle open circuit

Use Sigmaprobe to detect short circuit of automobile circuit

Short circuit to grounding

Grounding short circuit refers to the circuit grounding caused by insulation damage.
The wire grounding causes the fuse or fusible connection to burnout. If there is no fuse, the circuit can burn or even catch fire. If the short circuit occurs after the load, the circuit control device may lose its effect.
At this time, Sigmaprobe tester can help you detect more easily.
Remove the blown fuse from the fuse box. Use the Probe Tip to activate each of the fuse contacts.While the circuit breaker trips is a short circuit. Record the number or color of the wire. Trace the wire as far as possible.

Short circuit to electricity

A short circuit of the power supply refers to the contact between the wire and another circuit wire due to insulation damage.
This will cause the circuit to operate abnormally, causes some strange phenomena, and difficult to find. In order to find out such problems, we must observe the symptoms, use the Sigmaprobe tester to identify the relevant circuit, remove the fuse to help find out the relevant circuit branch, and then check the voltage and resistance at the key parts, so that the fault will be found.

Here is an example of this application.

If you are tracing a short circuit in the brake light circuit, you will know that the wiring harness must pass through the wire at the door sill, locate the color-coded wire in the harness and expose it. While in Component Activation interface selects MOMENT mode.
Use the Probe Tip to contact the marked wire, press the " UP " button to trigger the power supply. If the circuit breaker tripped, you have verified the shorted wire. Cut the wire and power supply each end with Probe Tip again. Follow the wire in the shorted direction and repeat this process until the short is located.

Here is an example of this application.

Use Sigmaprobe tester to detect and repair the fault of excessive resistance of automobile circuit.

Excessive resistance is often the most difficult fault to find. At this time, it is very important to use a Sigmaprobe tester. The loose, dirty, or corroded plug can cause excessive resistance and current reduction, resulting in dim or flashing light or failure of components.

As a kind of fault, excessive-high resistance means that the resistance in any circuit exceeds the original design index. High resistance is often caused by corrosion, looseness of terminals, connectors, and ground wires and insufficient contact are. High resistance can also occur inside the component. Excessive resistance makes the circuit load, and the additional load in the circuit will reduce the power supply of other loads in the circuit.

When the resistance is too high, the light will dim and the motor speed will slow down. In more severe cases, high resistance is like an open circuit. If the ground wire terminal is corroded, the ground wire (the resistance should be zero) will make all loads on the circuit unable to work due to its high resistance.

Water, dissolved snow salt, oil, grease, and dirt penetrating into the connectors often cause the high resistance of connectors, terminals and ground wires. The load may also cause high resistance due to internal damage, wear, overload or vibration. The internal resistance of this type of component is too high, just like the internal damage of the component, which is difficult to find with the naked eye. Some of the corrosion and oil stains on the connector, terminal and grounding can be seen, but some cannot be seen. At this time, You can use Sigmaprobe tester to check.

Sigmaprobe tester

Intermittent fault detection and maintenance of automotive circuits

Intermittent connection and poor contact.

Intermittent electrical faults in most circuits are caused by faulty electrical connectors and wires, or may also be caused by adhesion of components or relays. Check the following items before deciding whether to scrap a component or wire assembly.

1) Use the component activation function of the sigma probe detector to test and quickly determine whether the components are normal.
2) Whether the connector is installed and fixed.
3) The terminals extend or push out.
4) Whether the terminal on the wire assembly is fully inserted into the connector/component and locked in position or not.
5) Whether there is dirt or rust on the terminal or not. Corrosion and dirt may cause intermittent circuit failure.
6) Damage to the connector/component skin exposes the component to dirt and moisture.
7) Short circuit to ground caused by abrasion of conductor insulation.
8) The internal insulation of some or all strands is damaged.
9) Whether the internal insulation of the conductor is damaged or not.