Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSFORD1988AEROSTAR VAN PASSENGER, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ELECTRICALGAUGESINSTRUMENT PANEL - ELECTRONICTESTINGDIAGNOSTIC TESTINGTEST D
1988 Ford Aerostar Van Passenger, Automatic
Test D
1988 Ford Aerostar Van Passenger, AutomaticSECTION Test D
- Ensure engine is operating properly and is not misfiring. Depress and hold "GAUGE SELECT" switch. After 5 seconds, a tone will be produced, and tach option display will appear. Display will remain as long as switch is depressed.
- If option display appears. go to step 3). If option display does not appear, repeat step 1) (ensure "GAUGE SELECT" switch is fully depressed). If, after repeating test, display does appear, go to step 1) of Test W.
- Note position of tach read-out. If tach option read-out bar segments point toward 2000 RPM, tachometer is wired for use with 4-cylinder engine. If tach option read-out bar segments point to 3000 RPM, tachometer is wired for use with V6 engine.
- Verify that tachometer option display and engine match. If tachometer option and engine type match, replace tachometer and recheck cluster operation. If tachometer option and engine type do not match, tachometer wiring is incorrect. Go to step 5) or 7) depending on engine type.
- On vehicles with 4-cylinder engines, disconnect negative battery cable, and remove EIC. Check for continuity between pin 9C (circuit 398) and ground. See Figure . Continuity should exist at this point. Check for continuity between pin 10C (circuit 644) and ground.
- Continuity should not exist at this point. If continuity exists, replace tach/multigauge module and recheck cluster operation. If continuity is incorrect, rewire as necessary to create a ground at pin 9C (circuit 398) and an open at pin 10C (circuit 644).
- On vehicles with V6 engines, disconnect negative battery cable, and remove EIC. Check for continuity between pin 9C (circuit 398) and ground, and between pin 10C (circuit 644) and ground. Continuity should not exist at either point.
- If continuity is okay, replace tach/multigauge module and recheck cluster operation. If continuity is incorrect, rewire as necessary to create an open at both pin 9C (circuit 398) and 10C (circuit 644) and recheck cluster operation.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.