Auto electrical problems can be very difficult to diagnose. Yet it's important to approach any process of discovery in a logical way and look for the more obvious reasons first before assuming the worst. So, if something electrical on your vehicle appears to be at fault, where should you start?

Circuit Protection

The average vehicle has a number of independent electrical circuits in much the same way as the family home. These circuits connect large and small devices and sometimes have to deal with a considerable amount of electric current.

The larger or "hungry" components need to be separated from the rest of the electrical system until they need to be used. This is designed to protect the rest of the circuitry and make sure that the vehicle is as reliable as possible.

To isolate these larger components (such as the air conditioning system), engineers include independent relays. These are effectively miniature switches, and they will open or close whenever they receive a signal from either the ECU or the dashboard.

Relay in Action

Inside the relay are an electromagnetic coil and a simple, lever-operated switch. When the device in question is switched on, a low voltage signal is sent to the coil, activating the electromagnet. This magnet will then pull the lever towards it and, as it does so, will complete the circuit. This will allow the current to get to the device, and it will become active.

Identifying the Relay

Relays are quite reliable, but they can sometimes fail, and they should be the first port of call when trying to find out why something is not working. Most of the relays are found underneath the bonnet and near the bulkhead, and you will be able to identify the relay in question by referring to the user manual.

Manual Test

If you suspect that the relay may be faulty, place a finger onto the component as somebody tries to activate the device. You may be able to feel and even hear a "click," which means that the relay is energising but not completing the circuit. If you do not hear or feel any click, it is likely that the relay has failed, and you may need to swap it out.

An Alternative Approach

If you do not fancy the idea of sticking your finger near anything electrical (even though it is safe enough), take the vehicle to an auto electrical technician. They will have testing devices on hand to quickly diagnose the issue and fix anything necessary to get you back on the road.