Here's a breakdown of troubleshooting steps:
1. Check the Fuses:
* Locate the fuse box: Your Explorer likely has multiple fuse boxes – one under the hood and one inside the passenger compartment (often under the dash). Consult your owner's manual to find the exact locations.
* Identify the EATC fuse(s): The manual should list the fuse(s) responsible for the EATC system. Look for fuses labeled "Climate Control," "HVAC," or similar.
* Inspect the fuses: Check for blown fuses (a broken filament inside the fuse). Replace any blown fuses with fuses of the *same amperage rating*. Don't use a higher amperage fuse as this could damage the system.
2. Check the Battery and Battery Connections:
* Battery voltage: Use a multimeter to check the battery's voltage. It should be around 12.6 volts when fully charged. A low voltage battery can prevent the EATC from functioning.
* Clean the battery terminals: Corrosion on the battery terminals can restrict current flow. Clean the terminals with a wire brush and baking soda solution, then rinse with water and let them dry.
3. Check the EATC Power Supply:
* Wiring harness: Visually inspect the wiring harness leading to the EATC control unit. Look for any damaged, loose, or disconnected wires. Pay close attention to the connectors.
* EATC module power: This requires a multimeter. With the ignition ON, check for power at the EATC control module's connector. Your owner's manual or a wiring diagram will be essential to identify the power wires. A lack of power here indicates a problem upstream (fuses, wiring).
4. Check the blower motor resistor:
* A faulty blower motor resistor can sometimes prevent the EATC from functioning correctly, even if the fan is not working entirely. Locate the blower motor resistor (usually behind the glovebox) and visually inspect for any obvious damage. Replacing it is relatively inexpensive.
5. Check the Ground Connections:
* Poor ground connections can disrupt electrical signals. Look for ground points near the EATC module and ensure they are clean and secure.
6. Consider the EATC Module Itself:
* If all the above checks are fine, the EATC control module itself might be faulty. This is a more expensive repair, often requiring professional diagnosis and replacement. You may need a scan tool to read diagnostic trouble codes (DTCs) from the EATC module.
Important Considerations:
* Wiring Diagrams: Obtaining a wiring diagram for your specific 1999 Ford Explorer is highly recommended. This will significantly aid in tracing power and ground connections. You can often find these online or at auto parts stores.
* Professional Help: If you're not comfortable working with car electrical systems, it's best to seek professional help from a qualified mechanic. Incorrect repairs can cause further damage.
This troubleshooting process is a starting point. The exact cause could be more complex and require specialized tools and knowledge. Remember safety first – disconnect the battery negative terminal before starting any work.
