Radio problems

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ArizonaKid

ArizonaKid

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For a while now, i have had proplems with excessive noise and squeals coming from my radio, and i'm finally getting close to a solution. Everytime the car was running, the radio would put out a loud hum, and occasionally a loud, sharp, squeal. It made it impossible to use the radio.(sensitive hearing)
I started by installing a noise suppressor, and it helped a little.I tried using a different alternator, but that did nothing. The next thing was to replace the plug wires, which did help a lot, but did not completely solve the problem. Later today I am going to use a different alternator again to see what that does, most likely I will rebuild an alternator when I get the money.
I figured i'd post this so if anyone else had a similar problem, they could try what I did.
 
I also found out that when the field wires on the alternator are unplugged, the noise completely goes away.
 
I probably mentioned this before, but you did check all possible grounds for it right?

I think you have a problem with the radio, as a bunch of us are running all the same parts you are without it being a problem.
 
How old is the radio? Sounds like it could use an alignment. Old paper capacitors and drifting component values can cause unusual noises especially if the radio has been unused for several years. I'll bet you have radio issues as well as ignition suppression problems and it appears you have the ignition problems solved. It may be time to have that radio serviced.
 
I am using resistor plugs, i made sure to check that. And it could be a problem with the radio, but its a factory am/fm, so i am trying all i can to make it work before conceding to having it sent out.
 
I'd run a test ground wire from the neg batt terminal to your radio case... You don't mention what vehicle, but a lotta these vehicles have a rear support/ground on the radio,, that often is not secured after the radio is removed/replaced,, and tries to ground thru the 2 screws on the faceplate..

If that didn't cure the issue,, and the noise goes away with the the alt. field disconnected, it's likely an old points style (2 wire) regulator,, and the noise is likely from the points opening/closing.. I think I would replace the voltage reg with a transistor unit..

But do the ground test 1st.. this is sooo often overlooked

hope it helps
 
inertia said:
But do the ground test 1st.. this is sooo often overlooked

hope it helps
Click to expand...

I did, it helped some, afterward i replaced the ground strap, turns out it was missing, but it didn't completely solve the problem.
 
To me it sounds like something isn't grounded or shielded properly.

If you can, you could always remove the radio from the car and hook it up directly to a battery and a speaker using a few bits of spare wire laying around. Bypassing all the existing car wires could help eliminate the radio itself as the cause.
 
Well, since disconnecting the filed wires makes it go away, it has to do with the alternator.

OP, where did you put the noise suppressor? And is the humming a whirring note than goes up and down with the engine speed? How are the grounds under the dash?
 
nm9stheham said:
Well, since disconnecting the filed wires makes it go away, it has to do with the alternator.

OP, where did you put the noise suppressor? And is the humming a whirring note than goes up and down with the engine speed? How are the grounds under the dash?
Click to expand...

1: I got the suppressor off of the internet, its a bosch in line silver box suppresor.
2: yes
3: the grounds are good, we made sure when we took out the dash.
 
OK, the whirring in sync with engine speed is commonly an alternator whine. Since it went away when you disconnected the field, that seem to point to the alternator pretty conclusively.

Try this: run the car at night with the lights on, and see if the headlights dim more than usual when you drop the car to idle. I have to wonder if a diode is gone in the alternator, causing a lot higher than normal AC ripple on the output that is causing the whine. When you lose a diode, then the lights will usually dim more than normal at idle. The battery charging will also be weak.

You might also want to measure the battery voltage when running at fast idle and normal idle and let us know the readings. It might give a clue.....but might not.

Is the suppressor at the radio or at the alternator?
 
The other alternator i tried did not work, so im going to have to rebuild this one.
 
Got a whole lot closer, I rebuilt the alternator with an NOS capacitor and the low buzzing has completely gone, I still get a squeal every once in a while, but I think the problem is in the volume control, because if I work the knob back and forth, it goes away.

Also the alternator had two bad diodes, sooo I'm thinking that was a major part of the problem.
 
ArizonaKid said:
Also the alternator had two bad diodes, sooo I'm thinking that was a major part of the problem.
Click to expand...

No doubt!!!! Bad diodes, whether shorted or open, impress tremendous ripple (noise, spikes) onto the 12V line. This can actually damage / destroy electronic "stuff."
 
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