Section 375 (Defogger System): Inspection

WARNING: This page is about a different car, the 2004 Toyota MR2. However, it is still accessible from the selected car via links, so may be relevant.

Inspect Defogger Timer Operation
1. Connect the positive (+) lead from the battery to terminal 1 and negative (-) lead to terminal 4.
  
  Fig 1: Inspecting Defogger Timer Operation
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Connect the positive (+) lead from the battery to terminal 12 through a 3.4 W test bulb.
3. Turn the defogger switch ON and check that the indicator light and test bulb light up for 12 for 18 minutes, then the indicator light and test bulb lights go out.
  If the 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 the wire harness side, as shown in the chart.

Fig 2: Identifying Defogger Switch Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

DEFOGGER SWITCH SPECIFICATIONS

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

If the circuit is as specified, replace the switch.

Connector Connected: Inspect Defogger Switch Circuit

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

Fig 3: Identifying Defogger Switch Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

TESTER CONNECTION SPECIFIED CONDITION

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

If the circuit is as specified, try replacing the switch with a new one.

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

Inspect Defogger Relay Continuity

Fig 4: Identifying Defogger Relay Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

TESTER CONNECTOR SPECIFIED CONDITION

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

If the continuity is not as specified, replace the relay.

Inspect Defogger Wire

NOTE:

When cleaning the glass, use a soft, dry cloth, and wipe the glass in the direction of the wire. 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 5: Identifying Tester Probe
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Turn the defogger switch ON.

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

VOLTAGE CRITERIA

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

Fig 7: Checking Broken Wire Voltage

NOTE: If there is approximately 10 V, the wire is broken between the center of the wire and the positive (+) end. If there is no voltage, the wire is broken 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.
The point where the voltmeter deflects from zero to several V is the place where the heat wire is broken.
NOTE: 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.

If Necessary, Repair Defogger Wire
1. Clean the broken wire tips with grease, wax and silicone remover.
  
  Fig 8: Applying Masking Tape Along Both Sides of Broken Wire
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Place the masking tape along both sides of the wire to be repaired.
3. Thoroughly mix the repair agent (Dupont paste No. 4817 or equivalent).
4. Using a fine top brush, apply a small amount to the wire.
5. After a few minutes, remove the masking tape.
6. Do not repair the defogger wire for at least 24 hours.
  
  Fig 9: Applying Repair Agent to Wire
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002