1. Safety First:
* Disconnect the battery's negative terminal before performing any tests. This prevents accidental shorts and protects you from electric shock.
2. Visual Inspection:
* Inspect the module for physical damage: Look for cracks, burns, corrosion, or loose connections. A damaged module is often visually obvious.
3. Check for Power and Ground:
* Locate the module's wiring harness: Consult your vehicle's wiring diagram (a Haynes or Chilton repair manual is very helpful here). It will show you which wires are power, ground, and signal wires to/from the ignition coil and the crankshaft/camshaft position sensor (CKP/CMP).
* Use a multimeter to check for power and ground: With the ignition key in the "ON" position (but not cranking), check for battery voltage (+12V) on the power wire and a good ground (0V) on the ground wire to the module. If these are absent, troubleshoot the power and ground circuits *before* testing the module itself. A faulty power supply or ground will make the module seem bad when it isn't.
4. Check for Signal:
* This is the tricky part. The module receives a signal from the crankshaft position sensor (CKP) or a similar sensor (depending on your Capri's engine). You need a noid light or oscilloscope to verify this signal. A noid light will simply show you if the signal is present or not; an oscilloscope will show you the signal's waveform. This signal tells the module when to fire the coil. A missing or faulty signal will prevent the ignition from firing.
5. Resistance Testing (Limited Usefulness):
* Some modules can be tested using a multimeter for internal resistance. However, this is only a *rough* check. Your repair manual might specify resistance values to check for. But a reading within spec doesn't guarantee the module is good; it just means it's not obviously shorted.
6. Testing with a Known Good Module (Best Method):
* The most reliable test is substitution. If you can borrow a known-good ignition module from a similar vehicle (same engine!), swapping it in will tell you definitively if your original module is faulty.
If you are not comfortable with automotive electrical systems, it is highly recommended to take your vehicle to a qualified mechanic for diagnosis and repair. Incorrect testing can damage other components and even lead to injury.
Finding a Wiring Diagram:
A wiring diagram is crucial for this process. Try searching online for "[Your Capri's engine code] wiring diagram" (e.g., "2.3L Lima wiring diagram"). Haynes or Chilton repair manuals for your specific year and model Mercury Capri will also be invaluable.
