Car Automotive

Posts Tagged ‘system’

Automotive air conditioning is generally regarded as one of the two most significant contributions by American automotive engineering to the evolution of the automobile (the automatic transmission is the other). At first, air conditioning was an expensive option found only on the most luxurious automobiles.

As time went on, it became more available, and affordable, to the general motoring public. Today, air conditioning systems are such a widely used option that we seldom give them much thought, until they break and we have to fix them. And that’s what this book is all about – how to keep NC systems operating and how to fix them when they break. The heating system has also been included in this volume because it is an integral part of most modern automotive “climate control” systems. In many instances, it’s impossible to work on the air conditioning system without working on the heating system as well. But before we get into maintaining or servicing either system, it’s essential that you know the principles of air conditioning and heating system operation.

Make sure you understand them clearly before you try to maintain, diagnose or repair the air conditioning or heating system in your vehicle. Neglecting the material in this first chapter could get you into trouble later.

Without a good quality spark, in the right place at the right time, the engine performance will be affected, as will the operation of the emissions control system. A misfire can lead to unburnt fuel reaching the exhaust and this will quickly harm the catalyst, often irreparably. For this reason, modern systems monitor the performance of each cylinder, in relation to combustion.

One method of doing this is to ‘sense’ the angular acceleration of the engine flywheel; a firing cylinder will produce more acceleration than a misfiring one. In order to identify the cylinder that is misfiring the ECM requires a reference signal and this is often provided by the camshaft position sensor.

On modern systems, the ECM has the ability to detect misfires because the unburnt fuel that results can cause serious damage to the exhaust catalyst. The ECM achieves this diagnosis by reading the time interval between pulses from the crankshaft speed sensor. Persistent misfires will activate the MIL and a fault code (DTC) will be recorded. Urgent remedial work will then be required if serious catalyst damage is to be avoided.