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Matt, Engineer
Category: BMW
Satisfied Customers: 21711
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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I' Vine. I have a 1990 325i conv. My radio produces a

Customer Question

Hi I' Vine. I have a 1990 325i conv. My radio produces a hi pitched shrill noise . intermittently where do I look or what do I replace. Thanks
Submitted: 1 year ago.
Category: BMW
Expert:  Matt replied 1 year ago.


this is likley to be an interference issue with an electrical noise source contributing to the squeal

I'd 1st suggest checking that condition of the ignition / spark leads Check their resistance of the spark plug leads ( 13-15Kohm / metre) and replace if anydoubt or high resistance - Also replace the spark plugs if any of them failthis checklist:

there should also be a capacitor / damper on the coil power wire these look like little cylinders with 1 wire running to the power if the wire is broken or the part missing then your radio interference will increase markedly

also check the condition of the small earth wires that run out of the engine bay loom and terminate onto the engine with ring terminals

also check the condition of the fuse in the radio power wire if its connections need to be bright and clean with no resistance to the fuse

Customer: replied 1 year ago.
Matt thanks for your answer which confirmed my own theory. But I was expecting amore narrow answer.
I'not a mechanic so need more infomation.
Expert:  Matt replied 1 year ago.

Hello Vince

Ok 1st thing to check is the condition of the plug wires as they are the biggest influence

then check for the coil capacitor / damper and replace as required

Expert:  Matt replied 1 year ago.


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