UK Car Repair Questions? Ask a Mechanic for Answers ASAP
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By the description of symptoms, there is a low voltage condition, which may be from a weak battery, corroded battery cables, loose cable, corroded or loose engine or body ground, charging condition or short in wiring harness.
If you plan to diagnose the issue and repair yourself, you will need a digital voltmeter, good working knowledge of automotive electrical systems and ability to read wiring diagrams