[wolf_walker]

I've got a Becker 3302 in place of my 1492 in a 94 E320, it was cheap and the volume control works, mostly.

Noticed an odd thing, the volume varies by a pretty small degree all by itself, I don't know how to express it
but it's not even remotely like when the volume encoder goes bad on these, and it's without touching the unit,
just a slight but noticeable change now and then, quieter, louder, variable, not overly repeatable. Everything sounds and works
well otherwise, and the volume isn't popping up on the display when it happens so I'm pretty sure it's not some flavor
of the encoder acting up.

Stock fancy multispeaker stereo with the exception of a couple of aftermarket dash speakers using stock caps.

This ring a bell to anyone or just an old radio send it in for repair kinda thing?

 

[Skylaw]

You may have speed-dependent volume control that makes audio louder or quieter based on either 1) background noise in the cabin, or 2) the speedometer. Those sensing cabin noise use a microphone.

Alternatively, your volume control itself may be dirty or corroded - the dead giveaway for that is scratching and static in the speakers when you manually change the volume. If you're handy you might be able to use a cleaner on the volume control rheostat coil and contact in the radio.

 

[wolf_walker]

Nah, nothing like when the volume encoder goes bad(have several of them in the parts pile).
I checked the pin on the plug for speed sensitive volume and it's spot is empty
so I assume this 94 that came with a 1492 did not have it.

It's a peculiar fault, it sounds a lot like a radio station fading in and out, in fact exactly like that,
but it seems to have good reception overall. Guess if I had a cassette tape I could test that theory lol...