Radio static issues

[Litchkar]

I need help with a frustrating issue. My Retro Sound radio has static as if it is cutting out with the engine running. No issue with the engine off. No issue when streaming thru Bluetooth. I added another ground to the head unit, but no better. Changed dist. Cap and rotor too. Even ran a different antenna. Orange box ECM, 8 mm plug wires and resistor plugs. Radio has been in for 5 years, was fine until recently. Is it a car issue or a radio issue?

 

[Bret Schneider]

Run the car with the alternator belt off and see what happens.

 

[Litchkar]

Good call, removing the belt eliminates the noise. So how do I fix that?

 

[Bret Schneider]

The alternator probably has a bad rectifier. Either rebuild or replace the alternator.

 

[Litchkar]

Would an in-line noise filter help?

 

[Ricks72Chlgr440]

Would an in-line noise filter help?

View attachment 119197

Just replace the bad alternator and move on (assuming it is the alternator. Have it tested). Band-aids won't fix the root cause of your problem!

 

[Bret Schneider]

A filter might help a little but it won't fix the underlying problem with the alternator. The rectifier in the alternator consists of diodes which convert the alternating current (AC) the alternator is generating to the direct current (DC) the car's electrical system requires. When one of the diodes goes bad it "leaks" AC onto the DC in the form of ripple which is what is probably making your radio noisy. If you put a scope across the battery terminals you'd be able to see the ripple occurring on top of the DC ~14v signal. You can also use a good multimeter and set it to AC and the ripple will show up as AC on the meter. AC over 0.1v or so is an indication of a diode on it's way out.

Bottom line is fix what's causing the problem. If you want to keep the alternator you have any competent alternator repair shop should be able to do that. Otherwise just R & R it.

 

[Litchkar]

So… my Bluetooth started breaking up like the radio. Not wanting to drop close to 100 on an alternator right now. Took the chance and ordered the above filter on Amazon. Spliced it into the acc power lead and no improvement. Decided to try the always hot side (for the presets) and the problem is gone. I am sure that one day i will need an alternator, but this has been a year long battle, so I will watch it for signs of failure. Taking the win

 

[Bret Schneider]

The acc power input circuitry within the radio has some filtering built into it to attenuate the typical noise on a power line. The "noise" is sneaking into the radio through the keep alive power input as you have just discovered. So it's nice that the radio is quiet, but like you said you'll soon be needing a new alternator when the remaining diodes begin to fail as well. Keep a set of jumper cables in your trunk.