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 MANUALSMERCURY2010MARINER HYBRID, AWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 185 (HVAC CONTROL SYSTEM - GENERAL INFORMATION)DIAGNOSIS AND TESTINGCLIMATE CONTROL SYSTEMPINPOINT TESTSPINPOINT TEST F: NO COMMUNICATION WITH THE ELECTRONIC AUTOMATIC TEMPERATURE CONTROL (EATC) MODULETESTING
2010 Mercury Mariner Hybrid, AWD
Pinpoint Test F: No Communication With The Electronic Automatic Temperature Control (EATC) Module: Testing
2010 Mercury Mariner Hybrid, AWDSECTION Testing
WARNING: This page is about a different car, the 2005 Mercury Montego, 2005 Ford Freestyle, and 2005 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.
- F1 CHECK CIRCUIT 1203 (BK/LB) FOR AN OPEN
- Key in OFF position.
- Disconnect: EATC Module C228a.
- Measure the resistance between the EATC module C228a-1, circuit 1203 (BK/LB) and ground.
- Is the resistance less than 5 ohms?
- Yes : GO to F2.
- No : REPAIR circuit 1203 (BK/LB). TEST the system for normal operation.
- F2 CHECK CIRCUITS 483 (RD) AND 1566 (RD/YE) FOR AN OPEN
- Key in ON position.
- Measure the voltage between the EATC module C228a-26, circuit 483 (RD), C228a-14, circuit 1566 (RD/YE) and ground.
- Is the voltage greater than 10 volts?
- Yes : GO to MODULE COMMUNICATIONS NETWORK to diagnose the network concern.
- No : REPAIR circuit 483 (RD) or 1566 (RD/YE) for an open. TEST the system for normal 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.