- Noise is considered to be sounds that are not related to the normal operation of the cabin equipment and that affect the customer's satisfaction with the trip.
- Vibration refers to the impulses/jitter felt by the customer, which are independent of the road surface.
- Rigidity is such a character of the car's movement, in which the client clearly perceives the reaction of the car to the quality of the road surface.
Theory of diagnosis
Diagnosis is more than the exact following of a series of interrelated actions aimed at finding the cause of a particular problem state. It is a way to look for systems that are not functioning properly and determine the reason why this is happening. It is also about understanding how the system should work and whether it works correctly.
There are basic rules for conducting diagnostics. When following these rules, it is usually possible, by examining the system, to find the cause of a particular problem state the first time.
System Knowledge
- Knowledge of how elements fit/interact with each other.
- Knowledge of how the system works, as well as knowledge of its limiting characteristics/states and what will happen if the system does not work correctly.
- Sometimes this means testing the system against another system that is known to work correctly.
Knowledge of system history
Knowing any of the following can save time:
- How old or vice versa, how new is this system?
- What repairs were made?
- Has there been any maintenance/repair in the past that could lead to the current condition?
- What is the maintenance history of the system?
Knowledge of state history
- Did the problem start suddenly or did it build up gradually?
- Was the problem related to some other event, such as a collision or a previous element replacement?
- Knowledge of how the problem became known; it might be important "evidence" when looking for the cause of the problem.
Knowledge of the likelihood of developing certain conditions
- A simple cause is more likely than a complex one.
- For example: Problems of an electrical nature usually occur in the connections/connectors, not in the elements; The failure to start the engine is most likely caused by a broken wire or a slight misalignment, and not by a broken camshaft.
- Knowing the difference between the impossible and the unbelievable. Certain failures/faults in the system may be unbelievable, but they still happen.
- New elements are just new elements. This does not mean at all that these are always well-functioning elements.
Removing the symptom but keeping the cause
Reducing the front tire pressure may eliminate the vehicle's pull to one side, but will not eliminate the underlying cause of the problem condition.
Confidence in the found cause of the malfunction
- Double check
- What caused the element to wear out?
- A loose gearbox or engine mount may indicate that other mounts are also loose.
Diagnostic tables
Tables are the simplest way to express the relationship between the main logical and physical elements of a system. Tables help to find the cause of the problem state in the shortest possible time. Diagnostic tables combine multiple diagnostic zones into one "video sequence", showing:
- the probability of certain phenomena occurring in the system
- the speed of testing certain elements and functions compared to others
- ease of performing certain checks compared to others
- elimination of checking large parts of the system by performing simple checks
- narrowing the search area to a small "point" before deep checking
The fastest way to identify the cause of a problematic condition is to work with the available tools and instruments. This implies working in accordance with the diagnostic tables using the appropriate special equipment.
There are a number of testers available for use on Ford vehicles that are used to diagnose NVH problems. They are designed to detect mechanical noise, wind noise and noise such as squeaks and rattles.
The equipment is supplied under the FSE/Rotunda program.
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