[encantotom]

hi todd, that is a manual transfer switch. the 3 position switch allows you to have all power off, shore power or genny power.

it is just some relays, so if it is humming, the relay coils are getting worn. it will not hurt anything to hum.

i had the same thing on my 90 and i totally rebuilt it with new relays. i have the part numbers i believe if you choose to do so. it is not hard, just time consuming and the relays are a little pricey. i got mine from grainger.

tom

[Flick]

Why would I not hear that hum whenever I camp and plug into either 50 or 30?

[encantotom]

hi todd,

have a look at this.

i did this diagram after i rebuilt the 90 transfer switch.

i dont know if yours is exactly the same but i would guess it is probably very similar

tom

[Flick]

Yikes. Last time I saw something that complicated there was a spider in the middle of it! You give me far more credit for my abilities than I am due. Don't you think it's time for you and Darlene to see a South Dakota call. They are lovely. No leaves on trees with piercingly cold wind. Oh and I have this project for you.

Tom so you feel confident that this really loud hum is not harmless? I don't think I can get this done in time to get it in storage. So if I cannot get this done in time, which I can't, then can I use a battery tender and for this winter accomplish the same thing? If so tell me how to hook that up and what switches need to be in what position will you?

[encantotom]

no way can i tell you it is harmless. who knows what is harmless anymore.

when the relays are energized, which they are when shore power is applies, it is the relay coil that is making the buzzing. eventually if will likely just burn out and stop working and that could be in days or years. i doubt anything would come of it, but it is electrical so who knows. the buzzing on my 90 was there quite a while before i replaced the relays.

it really isnt that hard. it took me a few hours. you just have to take pictures and draw wiring diagrams before disconnecting anything. the relays, whether you have the ones i did or a slightly different ones are easily available. on mine there were auxiliary relays that attached to the main relay and the replacement ones were slightly different but appeared to be a better design.

it is actually a very clever and bulletproof design newell did on those manual transfer switches.

tom

[encantotom]

yours looks like it has 2 different contactors. you will just have to get the part numbers of each one and i can help you match them up with new versions.

tom

[prairieschooner]

Todd, I have exactly the same Contactor Box. I'll try another approach to explain this device.
This Contactor Box houses 2 Contactors (or Relays). It is controlled by a Switch (on mine) by the Driver's right Knee and has 3 Positions...Shore-Off-Generator. This is what would be referred to as a Source Isolation Panel.
I have heard a buzzing noise on occasion from this Box although usually when the Voltage coming in is Low. (look out here we go)However over time the Electrical Solenoid that activates the Contactors can have some wear. This is usually only in the Solenoid portion however the Contactors can have some pitting and this could also create some noise.

Are you trying to use a regular house outlet or 15-20 Amp Receptacle?

[prairieschooner]

PS the Contactors (Relays) may not be in production anymore. I have found some without the Auxiliary Contactors on ebay. Please be advised that the Auxiliary Contactors are very important so I am only using these for repair parts.
***The Auxiliary Contactors are what ensures that both Relays cannot be energized at the same time and are VERY important.
If I were to need a new Contactor I would go to an Industrial Electrical Supply with the Contactor in hand and ask about a replacement. They should have an interchange to ensure a proper replacement.

[encantotom]

steve, however there are functional equivalents that are nearly identical dimension and hook up wise. that is what i used.

tom

[prairieschooner]

steve, however there are functional equivalents that are nearly identical dimension and hook up wise. that is what i used.
tom

Yep, that is what I meant by an "interchange for a proper replacement". Mine are Square D although any 50 Amp Contactor with the correct Auxiliary Contacts (sorry I cannot remember if they are Normally Open or Normally Closed right now) should work