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.
Main Relay (Computer/Fuel System): Description and Operation
1991 Ford Aerostar 2WD V6-183 3.0LSECTION Description and Operation
The Engine Control Assembly (ECA) receives its operating voltage from the Electronic Engine Control EEC power relay.
When the ignition switch is turned ON, the normally OPEN contact points of the relay CLOSE and supply power to the ECA. The control coil circuit of the relay contains a diode, wired in series, to prevent relay operation if the battery polarity is reversed, preventing damage to the ECA.
RENDER: 1.0x
NO RELATED
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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.