Buzzing transfer switch

[MURPHY55347]

Replaced my smoked transfer switch with the same model. Southwire/Surgeguard 41300. This is a basic model. My MH is a 2018 Class A Vista LX 27N. Replacement was pretty easy and straightforward. This was done last October just before it got put away for the winter. This spring brought it home and plugged it in to 15A circuit and it worked fine. First trip of the year it worked fine. Took a trip just after Labor Day and plugged it in and it buzzed like crazy. Ended up cycling the pedestal CB and after 4 or 5 tries and the buzz was gone. Was the ok for the rest of the week. Thought it was just a fluke or perhaps it had something to do with higher than normal pedestal voltage. Was reading 127V. Plugged in again at home after the trip and it was ok. Getting ready for another trip this weekend, plugged it in only for it to start buzzing again. Plugged and unplugged a few times and all was well. This is on a15A circuit reading 117V. Any ideas what’s gong on??????
All wires are tight and properly torqued. Bought a torque screwdrivers just for this purpose.

[MURPHY55347]

So today we were headed out for the week. I decided to take off the cover to look at the relays. Pretty simple as there were only 2 screws holding on the relay cover. Manually
actuated the armature numerous times. Since this ATS is basically new, everything looked pretty pristine inside. Put together a set of tools to take with in case surgery was required. Got to the campground and plugged in and no buzz. Everything worked fine. So either that fixed the problem, the problem is intermittent, or the threat of surgery scared it into working. Thanks all for your advice.

[Grit_dog]

Yeah just replace it again.
Buzzing electrical circuits are not bueno.

[Veebyes]

Had the same buzzing problem. It eventually failed to respond to my hitting the thing to stop it. Nothing likes to be slapped.

Bought & installed a better quality, more expensive, unit. Silence for many years since.

[BB_TX]

What garyemunson said. Not unusual for any type open frame relay. And a transfer switch is just a special relay.

[garyemunson]

Dirt gets between the metal armature pieces. If they cannot "seal up" tight, metal to metal, they cannot develop a full magnetic field and will buzz. A common problem on RVs where road dirt gets into everything. If you are handy, you can take them apart (with power off!) and clean them. You do not want to let it continue since without the armatures in full contact with each other the current through the coil can increase enough for the coil to burn up. The buzzing also helps the wire connections to loosen and potentially burn up.

[larry_cad]

Talk to the vendor or manufacturer, but sounds like a defective transfer switch.