Therefore, you won't find a single switch you can manipulate. Instead, the relays themselves are likely located in one of these areas:
* Underhood fuse box: This is the most common location for fan relays. Check the fuse box diagram on the inside of the fuse box lid to identify the relay(s) for the cooling fan. They may be labeled or you may need to consult a wiring diagram.
* Passenger compartment fuse panel: Less likely, but some models put relays here. Check the fuse box diagram for this location as well.
* Integrated within the PCM: In some cases, the relay functionality might be integrated directly within the PCM itself, meaning there aren't individual relays to replace.
Troubleshooting a fan: If your cooling fan isn't working, you'll need to diagnose the problem systematically. Checking the fuse(s) is a good first step. Then, you might need to:
1. Check the coolant temperature sensor: A faulty sensor can prevent the PCM from sending the signal to turn the fan on.
2. Test the fan relay(s): If you locate the relay(s), you can test them with a multimeter to ensure they are functioning. Swapping with a known good relay from a similar circuit (if possible) is also a good test.
3. Test the fan motor directly: You can apply power directly to the fan motor (carefully, and only if you're comfortable with this kind of work) to see if it works independently. This eliminates a bad fan motor as a possibility.
4. Diagnose the PCM: A faulty PCM is less common but possible. This would require more advanced diagnostic tools.
A wiring diagram specific to your 1993 Oldsmobile Cutlass Supreme 3.1L is highly recommended for accurate relay location and troubleshooting. You can find these diagrams online (often through auto parts store websites or dedicated automotive repair sites) or in a repair manual specific to your car's year and model.
