When a grid is inoperable due to an open circuit, the area of glass normally cleared by that grid will remained fogged or iced until cleared by the adjacent grids. Use the following procedure to located a broken grid.
The ground wire is connected to the driver's side of the window and the feed wire connection is located on the passenger side of the window.
- With the engine running at idle, place the rear defogger switch in the ON position. The pilot lamp is the switch lever should light up indicating the defogger is operating.
- Using a 12 volt voltmeter, connect the positive lead of the voltmeter to the hot side of the vertical bus element on the inside surface of the glass.
- Connect the negative lead of the voltmeter to the ground side of the bus element. The voltage drop indicated on the meter should be 11-13 volts. Connect the negative lead of the voltmeter to a good ground, the meter reading should stay constant.
- Keep the negative lead connected to the ground and carefully use the positive lead to contact each grid at the approximate centerline of the window. A voltage drop of approximately 6 volts. indicates a good grid or a closed circuit.
- No voltage indicated a broken grid wire. To located the exact location of the break, move the voltmeter lead along the grid wire. The voltage should decrease gradually. If the voltage drops suddenly, there is a break at that location.
A grid repair kit 4106356, or equivalent is available from the manufacturer and the enclosed manufactures instruction should be followed for a proper grid repair.
TESTING GRID RESISTANCE
- Turn the defogger switch OFF . Use a ohmmeter (with a scale ranging from 0-100 ohms) to measure the resistance at each grid line between the center and the end, left and right separately.
- The section involving a broken grid line indicates resistance twice that in other information.
- Once in the affected area, move the tester bar for a position where the resistance sharply changes. Mark the broken grid line and repair as necessary.