Understanding the System:
The 1992 Ford Tempo's starter system uses a relay to handle the high current draw of the starter motor. The ignition switch sends a low-current signal to the relay, which then activates a larger switch inside the relay to connect the battery power to the starter.
Wiring Diagram (Simplified):
You won't find a single diagram applicable to every specific relay location in every car, but the fundamental principle is consistent. The relay typically has four terminals:
* Terminal 85 (or similar): Connected to ground. This is usually a chassis ground.
* Terminal 86 (or similar): Connected to the ignition switch. This receives the low-current signal when the key is turned to the "start" position.
* Terminal 30 (or similar): Connected directly to the positive (+) battery terminal (or a heavy-gauge wire directly from it). This provides the high current power to the starter.
* Terminal 87 (or similar): Connected to the starter motor's solenoid terminal. This is where the high current flows to activate the starter.
Replacement Procedure:
1. Disconnect the battery's negative (-) terminal. This is crucial for safety.
2. Locate the starter relay. This is usually found in the under-hood fuse box or a separate relay panel. Consult your owner's manual or a wiring diagram for your specific vehicle to be certain.
3. Carefully examine the existing wiring. Before disconnecting anything, take pictures or make notes on which wire goes to which terminal. This is *essential* in case you forget.
4. Disconnect the wires from the old relay.
5. Install the new relay. Make sure each wire connects to the same corresponding terminal on the new relay as it did on the old one.
6. Reconnect the battery's negative (-) terminal.
7. Test the starter. Turn the key to the "start" position. The starter motor should crank the engine.
Important Considerations:
* Heavy-Gauge Wire: The wires connecting the battery (+) terminal and the starter relay (terminal 30) must be heavy gauge to handle the high current. Using undersized wire can lead to overheating and fire.
* Grounding: A good ground connection (terminal 85) is critical. A corroded or loose ground connection can prevent the relay from working.
* Relay Identification: The relay may be marked with numbers (e.g., 85, 86, 30, 87) or may have a diagram printed on it. If in doubt, double check with the wiring diagram.
* Professional Help: If you are uncomfortable working with automotive electrical systems, it is best to seek help from a qualified mechanic. Incorrect wiring can damage your vehicle's electrical system or even cause a fire.
If you are adding a relay (highly unusual for this system), you'll need a more detailed wiring diagram specific to your intended modification. That would involve creating a completely new circuit using the relay to control some part of the existing starter circuit. This is a more advanced task.
