The 1997 Ford F-150 is a heavy-duty pickup truck. The F-150 is equipped with an air conditioning system, which cools the air before it enters the vehicle cabin. This creates a comfortable atmosphere within the cabin during hot weather. The AC compressor clutch provides the power to the AC compressor, which cools the air. If the AC clutch is faulty, the AC will not be able to properly cool the air. Test the AC clutch relay to ensure the clutch works properly to power the compressor.
Park the F-150 and turn the air conditioning settings to "off." Turn the engine off. Allow the engine and AC components to cool properly.
Open the hood and locate the AC clutch relay unit. Trace the wire that runs from the compressor -- this wire plugs into the clutch relay. The relay is found mounted on the firewall and has a three-wire connection.
Clip the test light to the truck negative battery terminal. Test each of the clutch relay lead wires with the test light lead. All should have a reading of "inactive," or depending on the test light, the light should not illuminate.
Turn the AC setting to the "on" position inside the vehicle. Go back to the front of the vehicle and unplug the compressor wire harness. Touch the test light to the three wires. The middle wire should read "hot" or the light should illuminate. The middle wire is the signal wire, which receives signals and power from the clutch. If the test light does not register or illuminate, the clutch is faulty and should be replaced.
