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 MANUALSMERCURY1998MOUNTAINEER 5.0 P, AWDREPAIR AND DIAGNOSIS (SINGLE PAGE)HEATING, VENTILATION & A/C (HVAC)HVAC CONTROL SYSTEMSHVAC SYSTEM - A/C-HEATER SYSTEM - AUTOMATICSELF-DIAGNOSTICSTEST L: TEMPERATURE SET POINT DOES NOT REPEAT AFTER TURNING IGNITION OFF
1998 Mercury Mountaineer 5.0 P, AWD
Test L: Temperature Set Point Does Not Repeat After Turning Ignition Off
1998 Mercury Mountaineer 5.0 P, AWDSECTION Test L: Temperature Set Point Does Not Repeat After Turning Ignition Off
- Check Memory Backup Supply To EATC Module
Turn ignition off. Disconnect EATC module connector C298. With a voltmeter, measure voltage of Light Green/Yellow wire between EATC module connector and ground. If voltage is more than 10 volts, replace EATC module and retest system. If voltage is less than 10 volts, go to next step. - Check Light Green/Yellow Wire Circuit For Open
Disconnect fuse No. 36 (7.5-amp) from instrument panel fuse panel. With an ohmmeter, measure resistance of Light Green/Yellow wire between fuse panel fuse No. 36 socket and EATC connector C298. If resistance is less than 5 ohms, replace EATC module and retest system. If resistance is more than 5 ohms, repair open in Light Green/Yellow wire and retest system.
RENDER: 1.0x
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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.