INSPECTION PROCEDURE 14: Noise: Noise is detected with engine running: Diagnosis

CAUTION:

Never connect a noise filter to the high tension cable (spark plug wire). Spark plug wires incorporate resistors which have the effect of suppressing noise. If a spark plug wire is found to be causing noise, it must be replaced.
Confirm that the noise is not from an external source.
Noise prevention should be performed by suppressing strong sources of noise first.

NOTE: Voltage surges can be induced in the electrical system by the collapse of a field (i.e. When power is removed from the coil in an A/C compressor clutch). This induced voltage surge will radiate a Radio Frequency (RF) signal that is picked up by the audio unit. In the case of the compressor clutch a "pop" will be heard through the speakers. The capacitor, installed on this vehicle, will store the excess voltage and prevent the production of RF noise. This is because the capacitor will charge and discharge as the voltage fluctuates. This has the effect of "attracting" noise and bleeding it to ground without interfering with the normal flow of current through the system.

DIAGNOSTIC CHART

DESCRIPTION OF NOISE	CONDITIONS	CAUSE	SOLUTION
AM, FM: ignition noise (popping, snapping, cracking, buzzing)	Increasing the engine speed causes the generator whine to speed up and the volume to decrease. Disappears when the ignition switch is turned to "ACC", and engine is off.	Electrical interference from the spark plugs. Engine noise.	Check or replace the ground cable. Check or replace spark plug wires. Check or replace the noise capacitor.
Other electrical components	-	Noise may intensify due to aging electrical components.	Repair or replace the electrical components.
Static electricity (cracking, crinkling)	Noise disappears when the vehicle is completely stopped.	Noise occurs when parts or wiring move and contact vehicle body.	Return parts or wiring to their proper position.
Static electricity (cracking, crinkling)	Various noises are produced depending on the body part of the vehicle.	This may be due to the recent removal of the front hood, bumpers, exhaust pipe and muffler, suspension, etc.	Properly ground parts. Properly ground all body parts.