1. Identify the Specific Fuse:
* Consult your owner's manual: This is crucial. It will tell you exactly which fuse controls the running lights and what amperage it should be. Don't just assume – get the correct information.
* Check the fuse box: Your Prism likely has an under-hood fuse box and an interior fuse box (often under the dash). Locate the correct fuse based on your manual.
2. Verify the Fuse:
* Check the blown fuse: Even if it looks okay, use a multimeter to verify it's blown. A blown fuse will show no continuity (infinite resistance).
* Replace with a fuse of the *correct* amperage: Using a higher amperage fuse is dangerous and could cause a fire. Only replace it with the exact amperage specified in your manual.
3. The Fuse Blows Again Immediately:
If the new fuse blows immediately after replacement, you have a definite short circuit. Here's a systematic approach:
* Running Lights Circuit: This is the most likely culprit. Start by inspecting the wiring for the running lights themselves. Look for:
* Damaged wiring: Check the wires running from the fuse box to the front and rear lights. Look for frayed wires, chafing against metal, or any signs of damage.
* Loose connections: Inspect the connectors at the bulbs and any other connection points along the wiring harness.
* Short to ground: A common cause. A wire might be touching bare metal or a grounded component of the car. This is harder to find and often requires careful tracing of the wiring.
* Dash Lights Circuit: While seemingly unrelated, the shared failure suggests a common point of failure, potentially in the wiring harness or a shared ground point. Trace the wiring for the instrument panel lights.
4. The Fuse Blows Intermittently:
If the fuse only blows occasionally, the short might be intermittent, perhaps due to:
* Moisture: Water ingress into a connector or wiring harness can cause intermittent shorts.
* Loose connection: A connection that's sometimes making good contact and sometimes not.
* Faulty light bulb: Although less likely to blow the fuse directly, a faulty bulb (especially if it's shorted) can draw excessive current.
5. Advanced Troubleshooting:
If you've checked all the obvious things and the fuse keeps blowing, you'll likely need more advanced troubleshooting techniques:
* Multimeter: Use it to trace the circuit, checking for shorts to ground at various points.
* Wiring diagrams: A wiring diagram for your specific year and model of Prism will be invaluable in tracing the circuits. These can be found online (often on forums dedicated to Chevy vehicles) or in a repair manual.
* Professional help: If you're not comfortable working with car electrical systems, it's best to take your Prism to a qualified mechanic. Improperly diagnosing and repairing electrical problems can be dangerous.
Important Safety Note: Always disconnect the negative battery terminal before working on your car's electrical system. This prevents accidental shorts and shocks.
By systematically checking these areas, you should be able to find the source of the short circuit and fix the problem. Remember, safety first!
