My 73 cutlass has the original AM radio with the antenna buried in the windsheld...when just sitting with the accessory key position on, the radio works fine....if the engine is running I get major static that drowns out the radio...Can anyone give me some idea of where to look or to begin looking? I wondered if there was something in the plugs or plug wires or possibly something in the alternator...many thanks
opos

 

I would start with the capacitor hooked to the positive terminal of your coil - I believe they are there specifically for what you are experiencing.
This thing:
https://www.ebay.com/itm/64-74-GM-OE...-/190824058276

 

I agree that you should start with the capacitor.

You can get one from Rock Auto for $5:

AIRTEX/WELLS
1B1011
$5.56
http://www.rockauto.com/en/parts/air...capacitor,7092

I found this one at NAPA's web site. Your local store may have it or be able to get it faster than Rock Auto.:

https://www.napaonline.com/en/p/ECHRR186

Radio Capacitor
PART #
ECH RR186

 

"FM... No static at all... "

 

if the coil capacitor doesent work some alternators had built in resistors for that, if its been replaced. its less expenisive to get a in line static surpreser for the powerline to the raido than replacing the alt

 

Static reduction is also the reason for resistor spark plugs and plug wires. If you have non-resistor plugs or wires then there will be a lot of static. I was once driving down the road and a really hopped up 57 Chevy passed by and my radio went out completely until after he passed. I suspected copper core plug wires, non resistor plugs, magneto, and such. That thing was a rolling EMI generator.

 

Ditto satellite radio. I haven't listened to a terrestrial radio station in any of my cars since 2004.

 

Thanks to everyone....I'm checking...my plan is for a radio swap out after while but just "tinkering" with the stock radio and wondered what might be the problem

Thanks again.

 

X2 on plugs and wires, most likely cause when maintenance was done on engine.

 

I use an MP3 player through my aux jack... Not a lot of good radio stations left that play my kind of music.

Make sure your radio grounds are clean and tight. AM radio is really sensitive to noise. There is also a big filter cap inside the radio that may be leaking. As the others stated, alternators can put out some high frequency noise, leaking spark plug wires, non resister wires and/or plugs, etc...

 

on the couple radios that I have just done, there is what appears to be a choke on the power line and before the amp section from the power supply.

All I have is an AM/FM SCM on hand (but they should be similar), if the chokes are bad, corroded, shorted etc, replace. they are listed in the SCM as .6ohm, and to get inductance from resistance, its just the reciprocal. L=1/R

in the power input there is also a choke on the AM RF section of the same value.

at home, during my testing, the power supplies and CFL and LED bulbs everywhere gave a lot of 120hz line noise, if you are hearing ign noise, it will be more of a higher pitched hum, 8 spark plug fires for every 2 rpm so rpm/2 * 8 = hz, and if its alternator noise and you have a contactor type regulator, its nearly the same formula but the multiplier is 2 or 3 depending on how many field coils it has (and I really dont know)

so it is the variable pitch him you are hearing, or static, which is random and everywhere? if its what I would call static, its likely one of the IF cans is bad - something inside, broken core etc and RFI noise is literally detuning the radio...(in a tube radio we'd call it silver mica disease, but Im pretty sure, no silver mica is in your radio unless this is a REAL OLD olds with a tube set...

oh also, there is a large film cap on the input as well, .47 ohms they are a little harder to get but not un-doable. look for either .47uf-50v (+) or in std markings 474k50

 

Start with the basics. If the windshield has been replaced the windshield connector may not be connected properly. I listen to a lot of AM radio and even on my 2013 Dodge truck there was a grounding problem that allowed major engine interference. A few things to look for are a proper ground at the antenna, a clean connector that plugs into the radio, and clean connections on any other splices. The windshield antennas don't have splices in them, or shouldn't anyway, they are only about 12~15 inches long. There should be two screws that hold the coax to the base of the windshield and a "snap" connector that connects to the windshield itself. If the screws that hold the coax end are loose or corroded/rusty the loss of shield ground will let all kinds of noise enter the center conductor. The connector that plugs into the radio should be clean and corrosion free as well. A light rubdown by hand or with a toothbrush should be enough to clean it. There isn't much else to the windshield antenna systems.

If you still have noise, determine which type it is, ignition static or charging system whine. Make sure the body to engine ground is clean and tight. Grounding is very important to noise reduction in all things automotive and is often overlooked. Metal body vehicles are much easier to work with than fiberglass like Corvettes and Avante's. If you have ignition static most of it can be reduced with a good tune-up. Points, condenser, resister plugs, and wires. Charging system noise can be even more hair-pulling than ignition noise. Make sure all of your charging system connections are clean and tight. Make sure the battery to engine block ground wire is clean and tight. If you have an external regulator, make sure it is working and grounded properly. If everything is in good shape, take the alternator to your local parts store and have it tested. All of the filters, capacitors, and choke coils in the world will not filter out the noise if the grounding, charging system, or ignition of the vehicle is in bad shape.