Rockford Fosgate 2300 Owner's Manual page 22

Problem
Engine Noise (Whine)
Solution
1. Disconnect the speakers from the amplifier. Connect a test
speaker to the amplifier output terminals. If the noise goes away,
check your speaker leads, speakers and crossovers.
2. If the noise persists, use a "shorting plug" to mute the input signal
at the amplifier. If the noise goes away:
a. Bypass all of the other equipment (i.e., crossovers and
equalizers) and connect the head unit directly to the amp. If
the noise disappears, reconnect the equipment one piece at
a time, being sure to test for noise after each piece is installed.
Logic indicates that the last unit installed when the noise
returns is the culprit. Refer to the unit's owner's manual for
more information.
b. If the noise persists, run a new RCA line from your head unit
to the amplifier. If there is no noise, replace the RCA cable.
c. If the noise is still present after replacing the RCA cable, run
the RCA cable on a different route.
d. Isolate the grounds on the head unit so that there is only one
grounding point. If the noise disappears, install the radio,
using only one (1) grounding point. Isolate the radio chassis
from the grounding on the dash, and use an antenna ground-
ing loop isolator on the antenna.
If noise persists, see your Authorized Rockford Fosgate Dealer.
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