When the rear defogger switch is pressed, voltage is applied
to the following components:
| • | The solid state timing circuit |
CKT 193 energizes the rear defogger relay in order
to close the relay switch contacts. This action applies voltage to CKT 293
and the rear defogger grid. Ground is supplied through CKT 850 for
Pontiac or CKT 900 for Oldsmobile. Oldsmobile also uses an antenna
choke in CKT 900. The rear window warms in order to remove the condensation
from the surface of the window.
The contacts in the timing circuit remain closed until one of the following
actions occurs:
| • | The rear defogger switch is pressed again. |
| • | The timer cycle completes. |
| • | The ignition switch is turned to the OFF position. |
When the rear defogger switch is pressed for the first time, the timing
circuit allows the rear defogger to operate for approximately 10 minutes.
Each time the rear defogger switch is pressed after the initial actuation,
the timing circuit operates for approximately 5 minutes. The timing
circuit resets to 10 minutes when the ignition switch is turned
to the OFF position.
