radio antenna TOYOTA SUPRA 1995 Service Repair Manual

3. RECEPTION PROBLEMS
Besides the problem of static, there are also the problems
called ºfadingº, ºmultipathº and ºfade outº. These problems
are caused not by electrical noise but by the nature of the ra-
dio waves themselves.
Fading
Besides electrical interference, AM broadcasts are also sus-
ceptible to other types of interference, especially at night.
This is because AM radio waves bounce off the ionosphere
at night. These radio waves then interfere with the signals
from the same transmitter that reach the vehicle's antenna di-
rectly. This type of interference is called ºfadingº.
Multipath
One type of interference caused by the bouncing of radio
waves off of obstructions is called ºmultipathº. Multipath oc-
curs when a signal from the broadcast transmitter antenna
bounces off buildings and mountains and interferes with the
signal that is received directly.
Fade Out
Because FM radio waves are of higher frequencies than AM
radio waves, they bounce off buildings, mountains, and other
obstructions. For this reason, FM signals often seem to grad-
ually disappear or fade away as the vehicle goes behind a
building or other obstruction. This is called ºfade outº. BE±82
± BODY ELECTRICAL SYSTEMAUDIO SYSTEM

 Problem No.
 Noise Noise produced by vibration or shock while driving. 30
  Noise produced when engine starts. 31
 Antenna Antenna±related. 32
 ANTI±THEFT SYSTEM Troubleshooting for ANTI±THEFT SYSTEM 33
HOW TO USE DIAGNOSTIC CHART
Is tape player operating
Is ACC applied to radio?Tape player faulty.
Check if GND (wire harness side)
to radio is OK.
Radio faulty.Radio assembly faulty.
Check if CIG & RAD fuse is OK.Replace fuse.
Is ACC applied to radio?
Is ACC applied to tape player?
Is ACC applied to power amplifier?
ACC wire harness faulty?
NO POWER COMING INRadio
(1) Audio system type and symbol used.
HINT: Confirm the applicable type of audio system.
(2) Symbol for type of audio system the question applies to.
HINT: If the audio system type is not applicable, proceed to next question below.
(3) Junction without black circle.
HINT: Proceed to next question below.
(4) Junction with black circle.
HINT: Proceed to question for applicable audio system type.
(5) HINT: Select question for applicable audio system type.
± BODY ELECTRICAL SYSTEMAUDIO SYSTEMBE±87

2 Radio POWER COMING IN, BUT RADIO NOT OPERATING
Is tape player operating normally?
Speaker wire harness faulty?
Speaker faulty?
Radio assembly faulty?
Hissing sound from speaker?
Radio assembly faulty. Recheck system after repair.
Radio assembly faulty.
Go to No. 32
Is power for the antenna
being output from the
radio or radio assembly?Radio assembly
faulty.
Is power for the antenna
being output from the
power amplifier?Power amplifier
faulty.
Is there continuity in speaker wire
harness
Temporarily install another speaker
Functions OK?
Power amplifier faulty. Recheck system
after repair.
± BODY ELECTRICAL SYSTEMAUDIO SYSTEMBE±89

3 Radio NOISE PRESENT BUT AM±FM NOT OPERATING
Is power for the antenna being output from
the radio assembly?
Is power for the antenna being output
from the power amplifier?
Radio assembly faulty.
Radio assembly faulty.
Radio assembly faulty.
Power amplifier faulty.
Power amplifier faulty. Recheck system after repair.
Radio assembly faulty. Recheck system after repair.
Go to No. 32
Is tape player operating normally?
Hissing sound from speaker?
BE±90± BODY ELECTRICAL SYSTEMAUDIO SYSTEM

Poor signals, poor location.
Radio assembly faulty.
Power amplifier faulty.
Go to No. 32.
Is tape player operating normally?Radio assembly faulty?
Speaker faulty.
Radio assembly faulty.
Hissing sound from speaker?Power amplifier faulty. Recheck system after repair.
Radio assembly faulty. Recheck system after repair.
Problem with radio wave signals or
location? (See SYSTEM DESCRIPTION)
Are both AM and FM defective?
Is power for the antenna being output
from the radio assembly.
Is power for the antenna being output
from the power amplifier?
Temporarily install another speaker.
Functions OK?
RadioEITHER AM OR FM DOES NOT WORK, RECEPTION
POOR (VOLUME FAINT), FEW PRESET TUNING BANDS
± BODY ELECTRICAL SYSTEMAUDIO SYSTEMBE±93

RadioSOUND QUALITY POOR
Is sound quality bad in
certain area only?Poor signals, poor
location.
Is power for the antenna
being output from the
radio assembly?Radio assembly
faulty.
Is power for the antenna
being output from the
power amplifier?Power amplifier
faulty.
Temporarily install another speaker.
Functions OK?
Is sound quality always bad?
Radio assembly faulty.Is tape player operating normally?
Radio assembly or power amplifier faulty.
Is tape player operating normally?
Go to No. 32
Radio assembly faulty.
Is speaker properly installed?Install properly.
Speaker faulty.
Radio assembly faulty.
Radio assembly or power amplifier faulty. Recheck system after repair.
BE±94± BODY ELECTRICAL SYSTEMAUDIO SYSTEM

Glass printed
antenna faulty.
Motor antenna
faulty
AntennaANTENNA ± RELATED
Does antenna extend when radio
switched ON?
Inspect antenna motor.
Temporarily install another antenna
Functions OK?
Inspect glass printed antenna.
Radio side faulty.
Antenna motor faulty.
Relay faulty.
Relay circuit faulty.
Inspect antenna motor control relay.
(Relay circuit)
Is power released to the antenna being
input to the antenna motor control relay?
Radio side faulty.
Check continuity between antenna motor
control relay and radio.Wire harness faulty.
BE±110± BODY ELECTRICAL SYSTEMAUDIO SYSTEM

ANTENNA ROD REMOVAL AND
INSTALLATION
1. REMOVE ANTENNA ROD
HINT: Do this operation with the negative (±) terminal cable
connected to the battery.
(a) Turn the ignition switch to ºLOCKº position.
(b) Remove the antenna nut.
(c) P r e s s t h e º A M º b u t t o n o n t h e r a d i o r e c e i v e r, a n d
simultaneously turn the ignition switch to ºACCº position.
HINT:
wThe rod will extend fully and be released from the motor
antenna.
wAfter removing the antenna rod, leave the ignition switch
at ºACCº.
NOTICE: To prevent body damage when the antenna rod
is released, hold the rod while it comes out.
2. INSTALL ANTENNA ROD
(a) Insert the cable of the rod until it reaches the bottom.
HINT:
wWhen inserting the cable, the teeth on the cable must
face toward the rear of the vehicle.
wInsert the cable approx. 400 mm.
(b) Wind the cable to retract the rod by turning the ignition switch
to ºLOCKº position.
HINT:
wIf the ignition switch is already in ºLOCKº position, do
step 1 (c) first, then turn the ignition switch to ºACCº
position.
wIn case the cable is not wound, twist it as shown in the
illustration.
wEven if the rod has not retracted fully, install the antenna
nut and inspect the antenna rod operation. It will finally
retract fully.
(c) Inspect the antenna rod operation by pushing the radio wave
band select buttons. BE±112
± BODY ELECTRICAL SYSTEMAUDIO SYSTEM

MOTOR ANTENNA CONTROL RELAY
INSPECTION
INSPECT RELAY CIRCUIT
Disconnect the connector from the relay and inspect connec-
tor on wire harness side, as shown in the chart.
 
 
Tester connection to
terminal number 
 Condition 
 Specified condition
 6±Ground Constant Continuity
 2±3 Constant Continuity 
 1±Ground
 
 Constant
 
 Battery positive voltage
 4±Ground Ignition switch position ON Battery positive voltage
 5±Ground Ignition switch position ACC or ON Battery positive voltage
 
 7±Ground
 
 Ignition switch position ACC or ON
and radio switch ON 
 Battery positive voltage
 8±Ground Ignition switch position ACC or ON Battery positive voltage
If circuit is not as specified, replace the relay.
± BODY ELECTRICAL SYSTEMAUDIO SYSTEMBE±113

  ANTENNA MOTOR CONTROL RELAY (Wire Harness Side) 
  1 ± Ground (Constant) Battery positive voltage
  4 ± Ground (Ignition SW position ON) Battery positive voltage 
  5 ± Ground (Ignition SW position ACC or ON)
 
 Battery positive voltage
  7 ± Ground (Ignition SW position ACC or ON and radio SW ON) Battery positive voltage
  8 ± Ground (Ignition SW position ACC or ON) Battery positive voltage
± BODY ELECTRICAL SYSTEMSERVICE SPECIFICATIONSBE±203