How to determine a faulty electrical circuit

Assuming that you have done all the 3 basic steps when checking for a faulty light and you fail to repair that light because there is no electricity supply going to the light itself. You should have confirmed this with your test pen. Let’s discuss what else could be at fault and find remedies for the fault.

Go back to basics.

A lot of electricians that I have worked with tend to put their knowledge into overdrive when checking for simple faults. They simply think too deeply. There can be 101 reasons why the light don’t work, and they know these reasons. So instead of going back to the basic step, they tend to overuse their knowledge and start checking for faults at some deeper points. In all fault finding, start from the very basic step.

Check the switch first.

The switch is the main source where the current comes and goes to the light. Open the switch that switches on the light. Check for electricity supply there. If indeed there is electrical supply coming to the switch, put the switch to “ON” position to check if electricity is passing through the 2 terminals. If there is supply in one terminal but not on the other even when the switch is in “ON” position, then the switch is faulty. Replace the switch and see if the light will work now.

There is No Electrical Supply to the Switch.

Highly not probable, but happens sometimes. If the electrical circuit to that switch is faulty, then many other lights will not work either. That is because one electrical circuit supplies current to as many as 10 light points, which is the maximum number as determined by the TNB. So if there is really a circuit problem, then at least few other light won’t work. If that happens, check your main panel to see if there is a particular circuit breaker that has tripped. Try pushing it back to the “ON” position. If it trips again, then there is something effecting that circuit.

Place all the switches to the affected lights in “OFF” position and try switching “ON” the circuit breaker again. It should work. Then one by one, switch “ON” the lights that were affected. When you come to that light that trips the circuit breaker again, then you can confirm that this particular light is causing all the problem. You should isolate this switch. Place a piece of tape or something over it so that others will know this particular circuit is faulty.

The switch is good, but there is no electrical supply to the light.

Now that will confirm that there is a breakage in the wires somewhere along the way from the switch to the light. Sometimes this happens when a mouse has chewed away the wires somewhere up inside the ceiling. To further make sure that it is this problem, get a piece of wire, connect one terminal to the switch and the other terminal to the light’s ballast. (the terminal where the live wire goes) Switch “ON” the lights again. If the light works, then the problem is confirmed. You have a broken wire somewhere. You can either call in the electrician to have the wires replaced or if you are up to it, I’ll explain how to replace the wires in my next entry.

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