It probably isn't normal to hear a hum, but it is annoying. The hum is probably coming from the transformer in the converter. The transformer changes 120 volt AC to 12 volt AC. The plates sometimes become loose and when magnetism from the AC current passes through the windings it causes them to vibrate. It should not cause any harm. You probably have heard florescent light fixtures humming for the same reason.

guess i need to just hum along, because it has done it since we owned it two years just annoying....thanks

If the transformer plates are put together with nuts and bolts you may be able to tighten them. I haven't messed with any for a long time so I don't know how they are put together now.

I have a MagneTek converter in my 1994 Funlite and the owner's manual says in the Q&A section about humming: "There is some inherent noise with normal operation of the ferroresonant transformer and is not cause for concern."

Did dealer give you a new battery since it was new?. I'm going through same thing

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