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Audio Systems/bought used car and stereo has odd crackle
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Question
hello, i just bought a used 1989 Saab and it has a pretty new alpine stereo installed. it works great until i turn on the motor. before the motor is turned on i can blast music as loud as the stereo can go. but after i turn on the motor it can barely reach loud enough to hear over driving without breaking up or crackling.
This almost certainly a fault in the power supply or earth, I would pop the unit out but leave it connected, connect a multimeter, set to 20 Volts DC, to the earth and power leads and see what variation accures from engine off, ignition on but not started, engine cranking and engine started.
It may show up a fault in the battery, alternator or battery connectors, earth lead, etc.
Should read about 12volts at rest, drop to 10v to 11v when on and drop to 9v to 10v when starting but rise rapidly to 13 volts with the engine on fast tick over and 13.8 to 14 volts when revved a bit.
Peter
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Answers by Expert:
Peter G. Lee
Expertise
Accessory installations including audio, security and lighting, general wiring and fault finding. Nothing specific to US car electrics such as ECUs or engine management systems please i.e. how do I get the radio out of a Saturn, we don't have Saturns in Europe so I wouldn't know.
Experience
11 years as a security and audio installer in the U.K.
9 years own company in South West of U.K. installing for a number of high street retailers incluing Trinity in-car centre, Road User, Halfords and A.1.
Past advisor to and chairman of Sold Secure initative gloucestershire police. member PACT (partnership against car theft)U.K. police,
Kit car builder
VW air coole
Organizations
Member of the institute of diagnostic engineers M.I.Diag.E
Education/Credentials
Certified by Clifford, Cobra (U.K.) Serpi Star-Gamel, Moss, Philips, Tracker (Lowjack), Pioneer blue chip installer, Kenwood installer.
City and Guilds, A.R.E
Past/Present clients
Over 2,000 between 1988 and 2000
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