Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

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Initial Inspection and Diagnostic Overview: Overview

Noise, Vibration and Harshness (NVH) is becoming more important as vehicles become more sophisticated and passenger comfort levels increase. This is designed to aid in the diagnosis, testing and repair of NVH concerns.

- Noise is defined as sounds, not associated with the operation of passenger compartment equipment, that interferes with customer's satisfaction.

- Vibration is defined as impulses felt by the customer that are not caused by road surface changes.

- Harshness is a ride quality issue where the customer feels that the vehicle response to the road surface is sharply transmitted to the customer.