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Q: 2004 Honda Civic LX. The entire electrical system pulsates with the engine. New battery and had the alternator tested.

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2004 Honda Civic LX..The entire electrical system pulsates, along with it the engine while driving. New battery and had the alternator tested three times..Replaced ground wires too..Been driving it like this since February. Sometimes it runs normal on any type of weather. No error codes detected. Some say its the main relay. Would the car even run with a bad main relay? What could be the problem?
My car has a manual transmission.

Hi there. From the description you have provided, your vehicle’s pulsating electrical system is an unusual problem. The main relay is not likely to cause your vehicle’s electrical issue. The fact you have been driving your vehicle this way for months leads me to believe that it’s not a hard component failure. Circuit tests need to be performed to help pinpoint the problem. The charging system control circuit could be the area of concern. I recommend having the electrical pulsation diagnosed and repaired by a certified technician, like one from YourMechanic.

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