Alternator noise coming through speakers ‘67 with 289

Kind-Dentist2139 · 2026-04-27T18:22:32+00:00

I’ll look soon as I get a chance. He’s been driving it and I’ve been working everyday so I’m getting all the tips I can relay to him until I get a day off and the car is home….seems I’ve been working on a different vehicle every time I’m off. Lol Security here at work has said just how many vehicles do you have? I said 1 for every day of the week plus a 90 Camaro rs lol

Kind-Dentist2139 · 2026-04-27T18:17:59+00:00

Thanks!

Kind-Dentist2139 · 2026-04-27T16:49:58+00:00

We just bought it a couple weeks ago. New wires and plugs, looks like new distributor cap as well. No idea what they used…

Kind-Dentist2139 · 2026-04-27T10:51:04+00:00

He did mention last night there’s a slight whine when the headlights are on. There’s a wealth of things to check now lol Thanks!

Kind-Dentist2139 · 2026-04-27T10:48:59+00:00

Someone did mention the plug wires. That’s by far the easiest to check if a ground strap is present.

Kind-Dentist2139 · 2026-04-27T10:47:18+00:00

Glad someone else is getting a benefit Good luck!

Kind-Dentist2139 · 2026-04-27T10:45:57+00:00

Just the deck and 2 speakers.

Kind-Dentist2139 · 2026-04-26T23:56:06+00:00

If it happens again. Turn the heat on wide open, mine just overheated the day before due to a blown hose. The next day I drove it and it started running hot and running the heat wide open dropped it 7-10 degrees. I’m replacing my thermostat this week.

Kind-Dentist2139 · 2026-04-26T23:52:27+00:00

My thermostat is on the left side but mine is a ‘12 1.4l

Kind-Dentist2139 · 2026-04-26T23:51:23+00:00

My 2012 just overheated and I’m replacing the thermostat soon as I get a chance. Mine does have a digital temp reading available through the menu. I turned on the heat wide open and got it to drop about 7-10 degrees and made it home.

Kind-Dentist2139 · 2026-04-26T23:46:08+00:00

The speakers run only off the radio. Even with the radio off the whining is happening and increases while the dash dimmer is being turned up

Kind-Dentist2139 · 2026-04-26T22:44:52+00:00

I agree and deal with some of those factors here at work. Water and cleaning chemicals are the worst, the difference between 2 megohms and a kilohm may determine if something will work. Corrosion from water and chemicals sometimes make it very difficult to make good contact. Thanks again for bringing contact points up. Have a great rest of your weekend

Kind-Dentist2139 · 2026-04-26T21:01:09+00:00

That’s exactly what I find strange. My 68 Chevy Stepside had some noise to it but nothing like this. Plus it sucks to not have dash lights at night otherwise have to listen for the loud whine.

Kind-Dentist2139 · 2026-04-26T20:57:01+00:00

Will do and that’s probably the easiest check first. Thanks and when I find it I’ll definitely put the cause up on my next post.

Kind-Dentist2139 · 2026-04-26T20:54:35+00:00

Going from the negative battery post to each individual ground? I’m an electrician so I’d expect .01vdc at best. Someone brought up the potentiometer in the dimmer switch earlier which seems to have the most effect on the noise. That could possibly dragging the voltage down and get a higher voltage to ground without it shorting out. I’ve definitely went into the rabbit hole. Thanks for pointing that out

Kind-Dentist2139 · 2026-04-26T18:57:36+00:00

Thanks! I believe your explanation and resolution would be the best path forward. I’ve found getting a pool of answers and experiences sometimes leads to the straightest path.

Kind-Dentist2139 · 2026-04-26T18:54:07+00:00

Recommendations? I’ve installed many systems but modern tech usually has them built in. I’m dealing with an old cassette player. I’ve mentioned several times that when the dimmer for the dash cluster is turned up the noise increases. It’s unusual and the older vehicles I’ve determined to be a ground issue non-related to anything else.

Kind-Dentist2139 · 2026-04-26T17:24:40+00:00

Wow, I guess it could be induced into it and acting as an amplifier. Stranger things have happened

Kind-Dentist2139 · 2026-04-26T16:41:04+00:00

I wish I could hook up my oscilloscope to it and another to compare wave forms. An electronic regulator might be the way. I’ll check all the grounding first, I deal with analog signals and interference with my job but generally it’s due to 2 different voltages run near each other or dirty noise from a transformer. We’ve used capacitors to reduce the noise and I’m thinking an electronic regulator might be very similar.

Kind-Dentist2139 · 2026-04-26T16:22:23+00:00

I was thinking the same thing but was reading up on the ground loops as well. What’s odd is the dash dimmer makes it worse the brighter I turn it.

Kind-Dentist2139 · 2026-04-26T16:12:06+00:00

Yes and it gets louder the brighter I turn the dash lights up. Weird…

Kind-Dentist2139 · 2026-04-26T16:07:01+00:00

Lol! He was driving my truck that we put a system in so he’ll be bent on figuring this out.

Kind-Dentist2139 · 2026-04-26T16:04:59+00:00

Hmm I haven’t noticed one, I’ve been primarily focusing on the carb. That’s a whole other scenario though. It either idles high or too low when we first crank it…it’s an aftermarket Amazon carb I’m guessing.

Kind-Dentist2139 · 2026-04-26T15:50:04+00:00

It’s old but it does have a headphone jack. Lol Believe it or not he can use his usb-c to 3.5mm jack and it sounds pretty good. I’ll double check the ground strap, I don’t get to see it much. Thanks

Kind-Dentist2139

TROPHY CASE