Section 393 (Defogger System): Inspection

WARNING: This page is about a different car, the 2004 Toyota Celica. However, it is still accessible from the selected car via links, so may be relevant.

INSPECT DEFOGGER TIMER OPERATION
1. Connect the battery positive (+) lead to terminal 1 and the battery negative (-) lead to terminal 3.
2. Connect the battery positive (+) lead to terminal 5 through a 3.4 W test bulb.
3. Turn the defogger switch ON and check that the indicator light and the test bulb light for 12 to 18 minutes, and go off afterward.
  
  Fig 1: Inspecting Defogger Timer Operation
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
If operation is not as specified, replace the switch.

Connector disconnected:

INSPECT DEFOGGER SWITCH CIRCUIT

Disconnect the connector from the switch and inspect the connector on wire harness side as shown in the chart.

Fig 2: Inspecting Defogger Switch Circuit

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

TESTER CONNECTION CHART

Tester connection	Condition	Specified condition
3 - Ground	Constant	Continuity
5 - Ground	Ignition switch LOCK or ACC	No voltage
5 - Ground	Ignition switch ON	Battery positive voltage

If the circuit is not as specified, replace the switch.

Connector connected:

INSPECT DEFOGGER SWITCH CIRCUIT

Connect the connector from the switch and inspect the wire harness side connector from the back side as shown in the chart.

TESTER CONNECTION CHART

Tester connection	Condition	Specified condition
5 - Ground	Ignition switch ON and defogger switch OFF	Battery positive voltage
5 - Ground	Ignition switch ON and defogger switch ON	No voltage

If the circuit is not as specified, try replace the switch with a new one.

If the circuit is not as specified, inspect the circuit connected to other parts.

INSPECT DEFOGGER RELAY CONTINUITY

TESTER CONNECTION CHART

Condition	Tester connection	Specified condition
Constant	1 - 2	Continuity
Apply B+ between terminals 1 and 2.	3 - 5	Continuity

If continuity is not as specified, replace the relay.

Fig 3: Replacing Relay

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

INSPECT DEFOGGER WIRE

NOTE:

When cleaning the glass, use a soft, dry cloth, and wipe the glass between the wires. Take care not to damage the wires.
Do not use detergents or glass cleaners with abrasive ingredients.
When measuring voltage, wind a piece of tin foil around the top of the negative probe and press the foil against the wire with your finger, as shown.

Fig 4: Inspecting Defogger Wire

Turn the ignition switch ON.
Turn the defogger switch ON.

Inspect the voltage at the center of each heat wire, as shown.

Fig 5: Inspecting Voltage At Center Of Each Heat Wire

VOLTAGE CRITERIA CHART

Voltage	Criteria
Approx. 5V	Okay (No break in wire)
Approx. 10V or 0V	Broken wire

HINT:

If there is approximately 10 V, the wire is broken somewhere between the center of the wire and the positive (+) end. If there is no voltage, the wire is broken somewhere between the center of the wire and ground.

Place the voltmeter positive (+) lead against the defogger positive (+) terminal.
Place the voltmeter negative (-) lead with the foil strip against the heat wire at the positive (+) terminal end, and slide it toward the negative (-) terminal end.

Fig 6: Identifying Special Tools
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
The point where the voltmeter deflects from zero to several V is the place where the heat wire is broken.

HINT:

If the heat wire is not broken, the voltmeter indicates 0 V at the positive (+) end of the heat wire but gradually increases to about 12 V as the meter probe is moved to the other end.