To find it:
1. Consult your owner's manual: This is the best place to start. The manual should have a diagram showing the location of all fuses and relays.
2. Check the underhood fuse/relay box: This box is typically located near the battery. The relays are often in a separate section within the box. Look for a diagram on the inside of the box lid.
3. Check the interior fuse box: This is usually located under the dashboard, often on the driver's side. Again, check the box lid for a diagram.
4. Look for a relay that is labeled: While not always explicitly labeled "blower motor high speed," you might find one marked "blower motor," "HVAC," or something similar. Sometimes the high and low speeds use separate relays, or even different circuits within the same relay. If you have multiple candidates, you could try swapping them with a relay of the same amperage rating from a less-critical circuit (as a test, with the ignition on; do not attempt this with the engine running).
5. Use a wiring diagram: If you can't find it visually, a wiring diagram for your specific 1996 Pontiac Bonneville is your best bet. These are available online (often for a small fee) through sites specializing in automotive repair information. These diagrams show the precise location and circuitry of all components, including relays.
Caution: Always disconnect the negative battery terminal before working with electrical components. Incorrectly identifying or replacing a relay could damage your vehicle's electrical system. If you are not comfortable working on your vehicle's electrical system, it's best to consult a qualified mechanic.
