Electromagnetic Interference (EMI) and Electrical Noise

Some electrical components/circuits are sensitive to electromagnetic interference (EMI) or other types of electrical noise. Inspect for the following conditions:

• A misrouted harness that is too close to high voltage/high current devices such as secondary ignition components, motors, generator etc-These components may induce electrical noise on a circuit that could interfere with normal circuit operation.
• Electrical system interference caused by a malfunctioning relay, or a control module driven solenoid or switch-These conditions can cause a sharp electrical surge. Normally, the condition will occur when the malfunctioning component is operating.
• Improper installation of non-factory or aftermarket add on accessories such as lights, 2-way radios, amplifiers, electric motors, remote starters, alarm systems, cell phones, etc-These accessories may lead to interference while in use, but do not fail when the accessories are not in use. Refer to Checking Aftermarket Accessories .
• Test for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a clamping diode.
• The generator may be allowing AC noise into the electrical system.