Hi-Pitch Squeal

Not likely, lights are 12v.

Have you tried locating this squeal?

CAn the squeal happen with any one light or just a certain light?
Have you recently upgraded to LED's?
Can you put a regular old incandescent in one light?
Testing would be
turn on light with LED.
A) Squeal
B) NO squeal
IF A) replace led with incandescent and repeat test.
Could be a bad or crappy led lights

Happens with any single light.

No changes to type of lights.

It's been doing this for a while now.

Sound seems to come from area of control & breaker panel
where I think inverter is located.

turn the breaker for the 120 to 12 volt converter off and see if the noise goes away. Could be a frequency issue with the converter

Chris

If it is a converter/frequency issue.... what can I do to correct? Don't really want to replace.

change to led

If it's the 120v - 12v side, changing to LED's may help, might just move the problem so the squeal happens when you turn on 5 lights, or run the pump..etc.

Is this a problem when running on battery or just shore power?

Any experience soldering on circuit boards?

You mention inverter, you have a built in inverter (ie: 12v to 120v) or do you mean the converter (120v - 12v)?

I meant CONVERTER....sorry for the confusion.

That's what I suspected. Does the problem happen when on 12volt only?

IMO this type of problem indicates something is likely to fail, may last another 20 years.. or 2 days.

Last time I was in a converter they are fairly simple devices, perhaps check and see if there are any TV repair folks around, you'd be surprised how many retired engineers make money on the side fixing electronics. Or find someone selling high end stereos on craigslist, often those folks are buying and fixing up old high end equipment for resale.

Our coach does the exact same thing as OP. On shore power. Noise is orig from breaker panel area. Never figured it out, just have lived w/ it.