1996 F-150, F-250, F-350, F-Super Duty and Bronco Workshop Manual
Heated Back Window Grid Wire Test
Using a strong light inside vehicle, visually inspect wire grid from outside. A broken grid wire will appear as a brown spot.
Run engine at idle. Set the heated back window switch and light (18C621) to ON. The indicator lamp should come on.
Working inside vehicle with Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent, contact broad (bus bars) red-brown strips on sides of rear window. The meter should read 10-13 volts. A lower voltage reading indicates a loose ground wire (pigtail) connection at grounded side of glass.
Contact a good ground point with negative lead of meter. The voltage reading should not change.
With negative lead of the meter grounded, touch each grid line of heated back window at its midpoint with positive lead. A reading of approximately 6 volts indicates that the line is good. A reading of zero volts indicates that the line is broken between midpoint and the positive side of the grid line. A reading of 12 volts indicates that the circuit is broken between midpoint of grid line and ground
Heated Back Window Switch and Light, Control Assembly Test
Ground Pin 4 and connect a jumper wire between Pins 3 and 2.
Apply power to Pin 2. The indicator should not light.
Momentarily actuate control to the ON position. The indicator should come on and stay on after the control returns to the normal position.
The indicator should go off under the following conditions:
If control is depressed to OFF.
If power to ignition switch accessory terminal is removed or approximately 10 minutes have elapsed.
Apply 12 volts power to Pin 5. The ISO bulb should light.
Heated Back Window Switch Connector, Bronco
Pin Number Circuit Circuit Function
1 186 (BR/LB) Heated Back Window Switch to Heated Back Window Grid
2 185 (BK) Battery Feed to Heated Back Window Switch and Grid
3 8 (O/Y) Heated Back Window Timing Circuit Feed
4 57 (BK) Ground Circuit
5 19 (LB/R) Instrument Panel Lamps Feed