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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21599
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Battery draining and crackling noise when running which appears

Resolved Question:

Battery draining and crackling noise when running which appears to come through speakers - noise goes when the car has been running for a while and battery has been fully charged by alternator.
Submitted: 1 year ago.
Category: Car
Expert:  Matt replied 1 year ago.
Hello I'd first check the easy things like is the boot light or any other interior light staying on then check that the main battery connections are tight and in good condition also check the earth strap to the engine / gearbox. Next I'd check the current drain aspect, the best way to find what circuit is causing the excessive currant drain is to fit a current sensing multimeter in series with the positive battery lead on the car and the battery, or use a current clamp meter on the battery positive cable. A typical current drain with everything off and un-alarmed should be around 0.05Amp and if its higher than this remove a fuse and re-measure, if measurement doesn't change then replace the fuse and remove the next. Once you've isolated the circuit with the excessive drain check the wiring connections and plugs to components and the wiring harness that runs by the engine bay fuse box - the wiring harness chaffs / rubs through and gets damaged - but its not always easy to see so be careful when checking..
Customer: replied 1 year ago.
Thanks for your reply. Why would the noise stop when the battery is charged?
Expert:  Matt replied 1 year ago.
That I'm unsure about its possibly a bad cell on the battery thats shorting internally but once all cellls are charged there's no potential difference to produce the noise? Or a faulty alternator that only makes the noise when its charging you could test the latter by popping off the alternator belt and breifly run the engine from cold to see if the noise stops if it does then get the alternator checked out by an electrical specialist
Expert:  Matt replied 1 year ago.
do you still need help?
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Customer: replied 1 year ago.
Very helpful - thanks
Expert:  Matt replied 1 year ago.
glad to help if you could please rate me with the star system?
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