Where is the rear window defogger relay on a 91 Chevy S10 Blazer?

The rear window defogger relay location on a 1991 Chevy S10 Blazer isn't consistently documented in a single, easily accessible location across all models. It's likely in the underhood fuse box or possibly in the interior fuse panel (under the dash), but there's no single definitive answer without consulting your specific vehicle's wiring diagram.

To find it:

1. Consult your owner's manual: This is your best first step. It should have a fuse and relay diagram.

2. Check the underhood fuse box: Carefully examine the diagram on the fuse box lid. Look for a relay labeled "Rear Defogger," "Rear Window Defroster," or something similar. The relay itself might also be marked.

3. Check the interior fuse panel (under the dash): If it's not in the underhood fuse box, check the interior fuse panel. Again, refer to the diagram.

4. Use a wiring diagram: A wiring diagram specific to your 1991 S10 Blazer's year and trim level will show the relay's location definitively. You can often find these online through forums dedicated to classic Chevy trucks or by purchasing a repair manual.

Important Note: Be very careful when working with electrical components. Disconnect the negative battery terminal before starting any work to prevent accidental short circuits.