Auto sensors, relays, control units spares

Sensors, relays, control units car parts – essential details on function, installation, fault diagnosis, and lifespan

Sensors, relays, and control units are electronic devices whose main function is to oversee the operation of many car systems. The first ones monitor particular changes in the working environment. The second ones power the required branches of electrical circuits. The last ones assess the readings they receive and send commands to corresponding devices.

The design of sensors, relays, and control units

Generally, automotive sensors consist of a sensitive element enclosed by a plastic body, to which a wire connector is attached. The operating principle of the sensitive element is based on various physical and chemical properties of different materials. For example, heater resistors are used to measure temperature and strain gauges to measure pressure. Devices which determine position and speed are based on the Hall effect, that is, the inductive or magnetoresistive properties of certain materials.

Relays generally have a plastic body with an electromagnet, inside of which are movable and stationary contacts. When the electromagnet is powered, it drives the movable contact which opens or closes the circuit.

Control units consist of a microchip with a CPU, analog-to-digital (ADC) and digital-to-analog converters (DAC), a housing, and connectors for wires. The microchip includes a storage device with software.

Maintenance tips

• Observe the torque specified by the manufacturer during installation. Many spare parts have a thread which can easily be damaged by overtightening.
• Always replace technical fluids on time. The contaminants they contain can build up on the sensitive elements of measuring devices causing them to operate incorrectly.
• You should always make sure that all elements in relays and fuses are properly attached. Loose fittings and the resulting vibrations have a devastating effect on elements of these parts.
• Occasionally clean connectors using special products. Their contacts can start corroding if exposed to dirt and moisture.
• Use only components that comply with the technical requirements of your vehicle.
• Avoid amateur repairs to your vehicle’s electrical wiring.

Malfunction symptoms

A variety of symptoms can indicate faulty components. For example, if a throttle position or fuel consumption sensor fails, the engine no longer runs smoothly. In particular, its power is reduced and it starts jerking during acceleration. The engine may even stall while changing gears. Rough idling occurs as well. Sometimes when a device fails, the corresponding warning light goes off on the instrument panel.

If a relay is broken, the equipment it controls generally won’t work. Conversely, in some cases it can no longer be switched off. This usually happens when movable contacts get stuck.

Faulty control units make corresponding assemblies operate incorrectly: fuel pumps, injection system components, etc. Sometimes, the engine won’t start. It is also impossible to perform self-testing of the unit.

Malfunction causes

Moisture and dirt may get into loosely attached connectors, which results in corroded contacts or a short circuit. When the housing isn’t airtight, the contacts of microchips become oxidised as well. Reckless handling of a vehicle, such as the removal of the battery terminal while the engine is running can cause voltage spikes and make the equipment burn out. It is also dangerous to let sparks get onto electronic devices or wring when performing auto body works involving welding.

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