Here's how to test them:
1. Visual Inspection:
* Locate the fusible links: These are usually found in the engine compartment's fuse box or near the battery. Consult your owner's manual or a wiring diagram for the precise locations of the fusible links related to the circuit you suspect is faulty. They often look like thicker wires than regular fuses.
* Check for obvious damage: Look for signs of melting, burning, discoloration (darkening or blistering), or a broken wire within the fusible link. A broken fusible link is clearly bad.
2. Multimeter Testing (if visual inspection is inconclusive):
* Disconnect the fusible link: Carefully disconnect the fusible link from both ends to isolate it from the circuit.
* Set your multimeter to resistance mode (ohms): Select a low ohms range (like 200 ohms or less).
* Test the fusible link: Touch the multimeter leads to the ends of the fusible link.
* Interpret the results:
* Low resistance (close to zero): The fusible link is good. It has a continuous path for electricity to flow.
* Infinite resistance (OL - open loop): The fusible link is blown (open circuit) and needs to be replaced.
Important Considerations:
* Safety First: Always disconnect the negative battery terminal before performing any electrical tests. This prevents accidental shorts and protects you from electric shock.
* Wiring Diagram: A wiring diagram is invaluable for identifying the correct fusible links related to a specific circuit. Without one, you might be testing the wrong link. You can often find these online through Ford F-150 forums or repair manuals.
* Replacement: Replace a blown fusible link with one of the *same* rating (ampere rating will be printed on it or nearby). Don't substitute with a different amperage fuse or wire. Using an incorrect rating could damage your vehicle's electrical system.
* Underlying Problem: A blown fusible link almost always indicates a short circuit or an overloaded circuit somewhere else in the system. Replacing the link without finding and fixing the root cause will likely lead to the new link blowing as well.
If you're uncomfortable performing these tests yourself, take your F-150 to a qualified mechanic. Electrical systems can be complex, and incorrect repairs can cause more damage.
