Troubleshooting Hints

TRY FOLLOWING CHECKS BEFORE DOING SYSTEM CHECK.
1. Check I/P Fuse Block IGN-3 (Buick) and HVAC CONT (Oldsmobile) Fuse by visual inspection.
2. Check Rear Fuse Block HTD MIR Fuse, BLK (150/151) and BRN (741) wiring if Heated Mirrors do not operate on Oldsmobile.
3. Check Rear Fuse Block Up 1 (Oldsmobile) and DEFOG RR Fuses by visual inspection. If the I/P 1 Fuse is open (Oldsmobile only), there is still a battery feed from the HZRD/STOP Fuse to the DIC Switch Assembly.
4. Check that connectors on Rear Defogger and Rear Defogger Relays are firmly mated.
5. Upper Zone Rear Defogger heats top half of rear window, Lower Zone heats bottom half of rear window.