* Under the hood, in the fuse box: Many Rangers of this era had a fuse box under the hood. Look carefully within this box – the relays are often grouped together, and may be labeled or you may need to consult a wiring diagram (available online or from a repair manual specific to your Ranger's year and engine). The relay might be labeled "A/C," "Compressor," or something similar.
* Under the dash, near the blower motor: Some Rangers might have the AC relay mounted closer to the AC system components themselves. This is less common, but check around the blower motor and associated wiring harnesses.
* In a separate relay center: In some cases, there may be a separate relay center somewhere in the engine bay, away from the main fuse box.
To find it with certainty:
1. Consult a wiring diagram: This is the most reliable method. A wiring diagram specific to your 1991 Ford Ranger will pinpoint the AC relay's location and often show its circuit. You can find these diagrams online (often for a small fee) or in a Haynes or Chilton repair manual.
2. Trace the wiring: Locate the compressor's wiring harness (it'll be a thicker harness going to the AC compressor itself). Follow the wires back towards the fuse box or other potential relay locations. This is a more time-consuming method.
3. Use a multimeter (advanced): If you're comfortable with electrical testing, you could use a multimeter to trace the circuit. Be cautious when working with automotive electrical systems.
Remember to disconnect the negative battery cable before performing any work on the electrical system. Always exercise caution when working near electrical components.
