When the ignition switch is in the ON position, voltage is applied from the IP fuse 21 to the HVAC control assembly.
When the defogger switch is pressed, voltage is momentarily applied to the defog request input of the solid state timer. The timer closes the internal contacts from terminal 3 to terminal 4 of connector C5 (for manual HVAC control) or from terminal D14 to terminal C10 (for Electronic Climate Control). The following actions then occur:
- The ON indicator of the switch lights.
- The coil of the defog relay is grounded using CKT 193.
The defogger relay coil is supplied with voltage through the IGN E fuse of the underhood bussed electrical center (UBEC).
When the relay contacts close, voltage is applied from the UBEC defogger relay terminal 30, pin 87 through both of the following fuses:
| • | The RRDFOG fuse to CKT 1093 |
| • | The HTDMIR fuse to CKT 2267 |
These circuits supply the following components:
| • | The rear defogger grid (finding ground at G420) |
| • | The left mirror grid (finding ground at G202) |
| • | The right mirror grid (finding ground at G205) |
The solid state timer within the HVAC control assembly controls the amount of time that the internal contacts are closed.
The defog cycle runs for 10 minutes when the following conditions exist:
| • | The ignition switch is turned to the ON position. |
| • | The rear defogger switch is turned to the ON position for the first time. |
Further operation results in 5 minute defog cycles. The defog cycle resets to 10 minutes when the ignition switch is turned to the OFF position and then turned to the ON position.
