Methods, with caveats:
* From the Coil (Most Common, but Requires Understanding): This is often the easiest method, but it requires understanding the coil's operation and potentially adding an adapter.
* Positive Trigger Coil: For many 1987 Wagoneers, the coil provides a positive pulse. You'll need to connect the tachometer's wire to the positive side of the coil. Caution: This method will likely only work with some older tachometers designed for this type of signal; many newer electronic tachometers need a different signal. Connecting incorrectly could damage your tachometer or the vehicle's electrical system. You might need a coil adapter to convert the signal for compatibility with your tachometer.
* Negative Trigger Coil: Some systems use a negative pulse. Connecting to the negative side of the coil might work for some tachometers, but this is less common. Again, consult your tachometer's instructions.
* Finding the Coil Wire: Locate the ignition coil; it's usually near the distributor (if equipped). The wire from the coil to the distributor is often the one you'll tap into. However, you'll need to determine the polarity (positive or negative). A multimeter can help here. Consult a wiring diagram for your specific year and engine.
* Distributor Pick-up: Some tachometers can interface with the distributor's pick-up signal. This often involves attaching a sensor to the distributor cap, requiring more specialized knowledge and potentially altering the distributor. This method is generally not recommended for someone unfamiliar with automotive electrical systems.
* ECM (Electronic Control Module): On fuel-injected models, the ECM may have a tach signal output. However, this is less common for older vehicles, and tapping into the ECM requires significant electrical knowledge and caution to avoid damage. You absolutely need a wiring diagram and deep understanding of automotive electronics for this approach.
What You'll Need:
* Wiring Diagram: Crucial! A wiring diagram specific to your 1987 Jeep Wagoneer's engine will show you the location of the coil and other relevant components. You can often find these online (e.g., through online forums or repair manuals).
* Tachometer: Make sure it's compatible with your vehicle's ignition system (positive or negative trigger).
* Wire Connectors and Crimps: For making safe and secure connections.
* Multimeter (Recommended): To test voltage and confirm polarity.
* Inline Fuse (Recommended): Protect your tachometer from potential electrical surges.
Before You Start:
* Disconnect the Battery's Negative Terminal: This is crucial for safety!
* Consult your Tachometer's Installation Instructions: The instructions should have specific connection diagrams and information about the type of signal required.
* If Unsure, Seek Professional Help: Wiring automotive electrical systems incorrectly can lead to damage or even injury. If you're not comfortable working with automotive electrical systems, take your vehicle to a qualified mechanic.
In short, the process isn't straightforward and requires careful attention to detail. The safest and most reliable approach is to find a wiring diagram and carefully follow the instructions for your specific tachometer and vehicle. A mistake can cause damage to your vehicle's electrical system or your tachometer.
