On the way to the cottage an intermittent screeching sound seem to come from the radio speakers. My first thought was the radio had brought it or some unknown security system had fired off. I knew such a system was not factory on 1984 300ds so I turned the radio off.

Screeching was still present on an intermittent basis. So as I drove along wondering what the hell was generating the high pitched screech in the audible spectrum. I noticed the cruise was starting to act up a very slight amount. That made me think the amplifier was probably voltage sensitive. Plus I had installed new belts reciently.

On arrival at the cottage sure enough the alternator belt had stretched causing intermittent alternator output. The no charge light on the dash did not illuminate at all as far as I could tell. Nor just glow dull. I couild have of course missed it as it was a bright sunny day.

So as the output voltage changed so did the cruise control vary a little in concert. Now how the high pitched ocillations were generated is an unknown. No doubt as the voltage dropped a little something was breaking into oscillation. I am not going to try to find it by the way. I just mentioned this for people to think about .Especially if any complaints of a high pitched squeels source are ever asked. Easier to restore the voltage on those cars rather than source the culprit I imagine.

Also could be one in a million type of thing. Although I thought maybe I remember someone asked before about a screeching sound that was not a belt or bearing.

Has there been any UFOs or alien "abductions" reported out there lately?

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Well just took the wife out for a quick supper and we just got back. It screeched again. Not once yesterday on the trip home. Turns out it is a warning that the sunroof switch has been left on but the warning is not constant.

The variation in voltage did affect the cruise function though. May have impacted the warning making it nore intermittent. It is now back to perfectly normal. Maybe tomorrow?

If only all intermittent problems resolved as easily. So obviously it must be some kind of dedicated buzzer located at the rear of the passenger compartment as far as I can tell. The audio is ominidirectional in effect. So it was hard to locate the source.

This car has some shade of green alien metalic color as well come to think of it.

I drive a 1995 E300 Diesel and am encountering what I can best describe as an electric humming noise which happens when the airconditioning is operating. The noise increases in pitch with increasing vehicle speed. When I switch the airconditioning to "economy" turning off the compressor, the noise goes away. My alternator belt appears to be tight and there are no other apparent electrical issues with the car. I would appreciate any hints or clues about what the cause of this may be.

Best regards.

I would attribute the oscillating nature of the noise to the alternator. But I have no idea how the noise possessed your radio and cruise control.

this might help
Use the 'loaded string applet to help understand the motion of waves and interference.

either you live in an an electromagnetic worm hole, or a combination of bad grounding and uninsulated alternator activity created an electromagnetic field around the chassis of your car. This would explain the possession of the speakers as they are coiled wires and a magnet and require either current flow or an opposing magnetic field to created sound.

any high tension electrical lines around?

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Perhaps it's just the little elves from the black forest running amock?cool:

On the 95 The first thing I would attempt is to find the location of the electrical humming. Any particular tune? I see you are a fairly new member and welcome. For your problem a serious search of the archives should be conducted. Thats if you have not done so yet. There are a lot of obsure items like yours in there.

I will try to restore the car to the fault modes. If your suspicion is correct space travel may be possible. From what you mention the field strength would have to be pretty intense.

As a general policy I do try normally to stay out of worm holes around here. Mostly because the wife tends to get upset If my location is not known for a few days. Now that can be a major problem..

Like where have you been honey? Dear I was away traveling in worm holes. Talking about the unknown I have a pretty good ideal that might not fly well already.

Yes we also have high tension wires locally. I will slip out this afternoon and shoot a few insulators off for a test.

All in jest my friend. A little levity goes a long ways somedays.

Have you considered using noise suppressing spark plugs? . . . .HeeHee . . . . ROFL