* The PCM itself: A malfunctioning PCM can prevent the fan from turning on.
* The fan relay: A separate relay controls power to the fan motor. This relay might be located in the underhood fuse box or elsewhere, often near the fan itself.
* Wiring issues: A short circuit or broken wire in the wiring harness leading to the fan motor is a possibility.
* The fan motor itself: The fan motor could simply be failing.
To troubleshoot:
1. Check your owner's manual: It might have a wiring diagram or specify the relay related to the cooling fan. Even if it doesn't directly identify a "fan fuse," it might point you toward related relays or circuits.
2. Locate the underhood fuse box: This is usually in the engine compartment, often near the battery. Examine the fuses carefully, looking for any that are blown (broken filament or melted). However, don't expect a labeled fuse solely for "cooling fan."
3. Look for a relay: The relay is usually a small square or rectangular component with multiple terminals. You'll likely need to consult a wiring diagram to identify the correct relay. A mechanic or online resource specializing in 1993 Mercury Topaz wiring diagrams will be extremely helpful.
4. Professional help: If you're not comfortable working with car electrical systems, a qualified mechanic is the best option.
In short, there isn't a simple "engine fan fuse" to replace. The problem is likely more complex and requires systematic troubleshooting.
