The Story of The Car Part 9: The Ancillary Controls

The Ancillary Controls

These help in driver comfort and the driving task. The driver’s seat adjustments are the key to effective use of these and any other controls. Not too close and not too far. 

Washer and Wipers.

As soon as you have a windscreen you need a windscreen wiper. Without the wiper any dirt, debris or water will remain on the windscreen and degrade your view. At night the problem will be made worse by glare caused by external lights.

The wipers blades themselves can accumulate dirt and debris which should be cleaned off the blade. This should be done with hot soapy water on a cloth. Doing this will extend the life of the blade and reduce the squeak of operation.

In cold weather with overnight freezing the wiper blades should be pulled away from the windscreen to stop the blade freezing to the screen. If the wipers are used and still frozen to the windscreen this can lead to the wiper motors shorting out.

The wiper will need to be served by a washer which in turn supplies the cleaning mix to the windscreen. The washer will be a small pump that is operated by the driver as required.

The washers sometimes clog up or misdirect. Normally this can be cleared and redirected by the use of a small pin.

The cleaning fluid should be appropriate for your vehicle and not washing up liquid.

  • Washing up liquid contains salt that can be corrosive.
  • Your vehicle washers will be cold and washing up liquid is designed to be used with hot water.

Besides washers and wipers to the front windscreen. Rear windscreen and headlight ones are available subject to make and model of the car.

Heating and Ventilation.

The most important function of the heating and ventilation system is the provision of fresh air. This is to prevent the driver from falling asleep. The next function is driver comfort.

There are two main systems.

  • Basic heating and ventilating
  • Full air conditioning.

Basic heating and ventilating:

  • This draws air in from a grill that is normally under the windscreen.
  • The air is then circulated around the vehicle through a series of ducts and flaps.
  • The distribution may be assisted and regulated by a fan.
  • The distribution will be to the windscreen, foot-well, central and side vents.
  • The air will be heated by using a heating matrix.
  • As your engine is probably water cooled some of this water is directed to the heating matrix.
  • You will normally need to let the engine warm up for a short time to get any useful heat.

See the manufacturer’s handbook for details relevant to make and model to get the best results for your vehicle. The basic system on most vehicles will have dust and pollen filters. 

There will also be a control to re-circulate the air if the outside air is polluted.

Air Conditioning:

In temperate climates like the UK air conditioning is sometimes regarded as a luxury. For the air conditioning to be effective needs the vehicle windows to be closed. When in use it drains power from the engine but driving with your windows open will also be a drain on power.

Full air conditioning systems offer cooling in the summer, heating in the winter and dehumidification (demisting). This is achieved by the addition of a cooling matrix. The cooling matrix allows the air to condense which achieves the demist function of the system.

If your windscreen is misting-up it means that there is a difference between the internal and external air temperature and the air is humid. 

  • If it is misting on the inside the air conditioning should be used to demist the windscreen
  • When it is misting on the outside the heating should be applied.
  • This often happens in the summer when the air-conditioning is set cool or cold.
  • The cold air from the air-conditioning condenses on the inside of the windscreen.
  • Adjusting the temperature upwards solves the problem.

Dashboard Instrumentation.

These maintain the legality and safety of your vehicle. Part of your visual scan should include regular instrument checks.

car instrument panel


This measures vehicle speed and hence allows the driver to maintain legality. Car makers will often set the legal maximum at the top dead centre of the dial.

Car Speed Learning To Drive

Speedometers accuracy can be affected by tyre size. A larger tyre than standard wheel will give a slower reading than you are actually travelling at. This could mean you are unintentionally speeding. Speed reading can also be affected by load, tyre pressure and wear.

A new tyre will have a tread of 8mm; UK legal is 1.6mm this gives a difference on the diameter of 12.8mm (2*6.4mm). Your speedo’s accuracy is plus or minus 10%. They are usually set to read high by average error to ensure legality. Or put another way a speedometer should always read faster than the actual speed of the vehicle.

A driver’s speed will rise and fall with the gradient of the road for any given accelerator pressure. A quick scan that includes the instruments will help maintain legality.


This records the distance travelled by your vehicle. Your vehicles value will be dependant on the distance travelled among other things. The process of turning the odometer back to a lower value is called clocking and is done to increase the value of the vehicle. This is normally a criminal offence.

For this reason mechanics should record the odometer reading on any documentation they produce for you. By recording the distance travelled you are able to have your vehicle serviced at the appropriate intervals.

There may be a separate odometer called a trip, trip meter or trip odometer. This can be used for recording individual journeys. Possible reasons for this are measuring fuel usage or the mileage or points between turns for navigation.

Temperature Gauge.

There is a need for 2 temperature reading in your vehicle.

The engine temperature.

  • When it starts approaching the red zone indicates your engine is overheating.
  • If this happens stop where safe and make the necessary adjustments.
  • Call professional help if needed.

The gauge measures the water temperature round the engine. If the water level is not maintained by regular maintenance there will be no water for the gauge to measure. This could mean your engine overheating and no indication from your temperature gauge.

The second temperature you need to be concerned with is the outside one. Not all vehicles have this but it is very useful to know when it is starting to freeze outside.


Sometimes known as a rev counter, it can also be called the RPM gauge. This measures the revolutions of the engine.  If these were to become too high it would result in excessive engine wear and possibly even engine failure.

The high end of the dial is normally shown red. Hence this gives rise to the term `redlining` meaning that the engine and consequently the vehicle is being driven at the edge of its limits. Most modern engine will have an inbuilt limiter to prevent damage to the engine.

High RPM will mean high fuel usage and a limited response from the gear you are in. Knowledge of the RPM can help you save fuel. It can also help select the gear that gives the best response from the foot controls.

Fuel Gauge.

This shows the level of fuel in the tank. It can seem to be very inaccurate as they are designed to move slowly off the full mark. This is to give the impression of better fuel economy. Also when the gauge gets down towards empty there seems to be a bit more fuel than you thought.

Next time it is low top up and note the difference between what you have put in and what the manufacturer’s handbook says is the capacity of the tank. You will then have a more accurate picture of the fuel left in your tank.

Generally it is better to drive with a full tank than one that is near empty. You are less likely to run out of fuel. You will always have enough to cover the unexpected journey or delay. Any residual impurities will be more concentrated on low fuel levels. 

By running the tank on low levels the pump within the tank is not always covered. This may mean your pump is running hotter, which over a long period of time can cause failure.

Warning Lights.

Sometimes gauges and instrumentation can give too much information to be of use. So these are now replaced with a series of warning lights. Red will indicate immediate danger and amber warning. 

These will vary by make and model and the vehicle handbook should be consulted for a full explanation of all lights. You should be familiar with the warning lights before driving.


ICE (In Car Entertainment).

This is the collective name for a series of devices that provide audio/visual entertainment as well as automotive navigation systems (sat nav). Included are radio, CD, MP3, TV, DVD and video game consoles. The purpose of these is to increase driver (or passenger) safety or comfort. Where possible they should be removed from your vehicle when parked.

Audio Systems.

These should not be set so loud that they drown out what is happening around you. By the same token headphones should not be used by the driver. Beware of leaning to change setting or music when your attention should be on the road.

Visual Systems.

TV, DVD players and the like. When positioned in the front they should not be used when moving in order not to distract the driver.

Sat Nav.

It should be placed out of the way of airbags. Use of the sat nav should not stop your normal observations or driving. Use of speed camera alert should not result in speeding. To slow down before a speed camera is an indication to police that you are deliberately speeding with the intention of breaking the law. 

Be aware those short routes are different from quick ones. A quick route may use fast roads while a short one may include many junctions. 

The sat nav function on a mobile phone can be disabled by using the phone function. This can result in missed turns.

Mobile Phones.

They should not be used while your vehicle is moving. In conversation with your passengers in your vehicle, they will be aware of oncoming hazards. In your vehicle during a phone conversation the other party will not be aware of your situation.

Furthermore they could be imparting information to you that will distract you from the driving task.

The difference between using a mobile phone and a RT Radio device is that of legal exemptions and clearly defined use. For example both police and taxi drivers have a legal exemption to use a RT Radio device in the course of their work. Also the nature of the communication will be task specific.


There will be many other ancillary devices which will vary according to the make and model of your vehicle. Refer to The Manufacturer’s Handbook for a proper explanation. In addition many vehicles may be fitted with data terminals and other devices for work purposes.

All devices within the passenger compartment should be secured. In the event of a collision an unsecured device will still be travelling at your vehicle’s original speed.

Where possible device displays should not reflect on to the windscreen as this is a distraction from the driving task. Devices when not in use and unattended should where possible should be removed.

© Liam Greaney