philippfriedrich8
Ford Focus Undervoltage Issue
Summary of the thread
A 2004 Ford Focus is experiencing an undervoltage issue, leading to poor starting, system failures, and weak lights. The suspected cause is a heavily discharged or defective battery. After checking the battery terminals and considering the battery's age, it was suggested to test the battery's voltage while the engine is running. A workshop confirmed the battery was defective, and replacing it resolved the issue.
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4 comment(s)
philippfriedrich8 (community.author)
Thanks for the quick reply. I haven't checked the voltage while the engine is running, only when it's off, and it reads around 11.8V. The battery is about 4 years old, so getting on in years. What exactly was the problem with your Focus when you had these symptoms?
jessicahofmann3
With your voltage reading, I'd say it points to a defective power supply. Same thing happened to me, the system was showing low voltage. After some investigation I brought mine to a workshop. They load-tested it and the battery failed. Replacing the battery solved it. Given your battery's age and those symptoms, that would be the next logical step.
philippfriedrich8 (community.author)
Thanks for confirming. I suspected the battery, but wanted to rule out other possibilities. I took your advice and brought it to a workshop. They confirmed the battery was heavily discharged and defective. Replacing the battery (cost 290€) resolved the undervoltage issue and all related symptoms.
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FORD
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FOCUS
jessicahofmann3
Sounds familiar. I had similar issues with my Focus. Voltage drop can cause all sorts of weird electrical problems. Have you checked the battery's voltage with a multimeter while the engine is running? It should be around 13.5-14.5 volts. Also, how old is the battery itself?