Localizing an open-circuit

WARNING: This page is about a different car, the 2004 Volvo S40, 2003 Volvo S40, 2002 Volvo S40, 2001 Volvo S40, and 2000 Volvo S40. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Localizing An Open-Circuit In Rear Windshield

Courtesy of VOLVO CARS OF NORTH AMERICA.

Try to find the heating element(s) that are not functioning.

Determine the precise position of the open-circuit. Use a test lamp or a multimeter as follows:

Switch on the ignition.

Set the light switch to the off position or the parking position. This is to minimize the draw from the car battery.

Switch on the rear windshield defroster.

Position the test lamp "crocodile clamp" or the multimeter terminal pins on the input cable terminal on the left or right side of the rear windshield.

Fault-trace from the opposite side of the heating element by moving the point of measurement.

Only fault-trace half the width of the windshield to determine whether the test lamp lights or the multimeter gives a reading.

If the test lamp goes out or the multimeter does not give a reading, the point of the open-circuit has been passed. Move the point of measurement back. Determine the point of the open-circuit.

Use tape to mark the position of the open-circuit.

The set point of measurement must be moved to the other side of the windshield to measure the other side. This also applies if there is more than one open-circuit on the same heating element.

Fault-trace the entire windshield. Mark any open-circuits before repairing the heating elements.

Replacing the rear windshield

Do not repair a heating element if the open-circuit is in excess of 2 mm.

Replace the windshield if the open-circuit is larger than 2 mm. See Removing the rear windshield and Installing the rear windshield .