Pontiac Fiero 1988 Service Manual page 1161

I
NOISE SYMPTOM TABLE
2
SYMPTOM POSSIBLE CAUSE
REPAIR ACTION
Harsh popping noise that changes with
engine
rpm
Ignition noise Perform the steps under Ignition noise, page 150-9
High whine (like a siren) that changes
with
engine
rpm
Generator noise
Add filter package 1224205 to power and/or memory lead to the Radio (See Fig.
2, page 150-9)
By-pass the Generator output with 250 MFD l O Ov capacitor (See Fig. 3, page
150-8)
Install a dedicated ground strap on the Radio (See Fig. 1, page 150-9)
Run a direct wire from Battery ( + ) to Generator
Exchange the defective Radio with a good Radio. If noise disappears, send the
defective Radio for repair
Replace Generator
Noise occurs only when an accessory is
on
Condition in that accessory
Install filter package 1224205 in the power lead(s) to that accessory (See Fig. 2,
page 150-9)
Install a .5 MFD by-pass capacitor and power lead to that accessory
Consult Delco Sound Service Guide
AE stations weak, noisy, both A M and
F M
Defective Antenna or lead-in wire
Temporarily replace the Antenna with another one. Repair/replace the defective
one if the Radio reception improves
Check at the Antenna Coax lead-in and the connector
A M
only,
weak
& noisy AM alignment Remove Radio for repair
F M only, weak & noisy
FM alignment
Remove Radio for repair
Noise present with engine not running ECM or Digital Cluster
Install filter package 1224205 in the power leads of the Electronic Control
Module (ECM) and/or Instrument Panel Digital Cluster
Noise that stops when Antenna is
unplugged from the back of Radio
Antenna noise
Replace defective Antenna with a good Antenna
If noise disappears repair/replace the defective Antenna
Check Antenna ground, Coaxial Cable Braid, and grounds at connectors
If noise presists with replacement Antenna, the problem must be repaired at the
source of the noise (Generator, Ignition System, accessory, etc). See Delco Sound
Service Guide for noise "sniffing" procedures
30
O