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Old 11-04-2008, 07:45 AM   #1
Join Date: Jul 2003
Location: Durham, NC
Posts: 93
My transfer switch is humming and getting louder. Should I replace it and does anyone know of an upgrade?

Richard and Cris
Durham, NC
2004 Alpine Ltd. 36 mds
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Old 11-04-2008, 07:45 AM   #2
Join Date: Jul 2003
Location: Durham, NC
Posts: 93
My transfer switch is humming and getting louder. Should I replace it and does anyone know of an upgrade?

Richard and Cris
Durham, NC
2004 Alpine Ltd. 36 mds
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Old 11-04-2008, 09:09 AM   #3
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Join Date: May 2004
Location: Auburn, CA, Havasu, AZ & Mulege, BCS
Posts: 5,172
If in fact that's true, then a) yes, and b) right away. Xfer switches shouldn't hum; to do that they would have to be generating heat and that's not a pretty thought.
Could be something else that's humming. If you can put your hands on the switch housing and feel vibration, then see above (if no vibration there, feel around elsewhere for the vibration associated w/the hum). B4 replacing, try shutting off all power on both sides (inverter as well as incoming 120V or 240V), then open the switch housing and tighten down the connections on incoming and outgoing wires, then close the box & re-energize. If that doesn't fix a hum, then the booger is asking for early retirement and its wish should be granted.
Baja-tested '08 2-slide 36'
Alpine: The Ultimate DIY'er Project
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Old 11-04-2008, 09:54 AM   #4
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Alpine Owners Club
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Location: Las Vegas, NV
Posts: 1,097
I am not sure if the power, used internally, to operate the contactor's control circuit is AC or DC. If it is AC, then the contactors will hum as they get older. I have never seen them heat up from this, they just create a very annoying noise. On all of the humming contactors I have seen the contacts are still holding fine. The humming is created by the AC causing the core and part of the contactor that supports the contacts vibrating against the coil and base. The contacts on the contactors can burn with age also.

If you know what you are doing, checking which contactor is making the noise and replacing it is quite simple. If not, just buy a new complete unit.
Dale Gerstel
2007 Limited SE 40fdts
Las Vegas, NV
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Old 11-04-2008, 01:11 PM   #5
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Join Date: May 2008
Location: Chatsworth CA
Posts: 160
I have the Surgeguard transfer switch and it stopped passing the secondary leg when connected to shore power. This is the leg that powers the front A/C and the washing machine. The transfer switch consists of two three contact relays which are normally open. One is connected to the generator and one is connected to the shore line. They both connect to the coach power. The AC power itself operates the respective relay to pass the power through. There is no DC connection. The box contains other electronics to function as the surge and voltage protection, time delay etc. In my case, the shore power relay had a bad contact that would not close sufficiently. I could push the button on top of the relay that physically closes the contacts and that would do it but under power it stayed open.

When I first opened the box I noticed that the wire from the shore line was loose and that may have contributed to the problem. Fortunately, Surgeguard repaired the unit under warranty. I am in the process of re-installing the unit using plugs and receptacles so I can wire it on the bench and just plug in three connections. This allows me to bypass the unit if it ever fails again just by switching plugs.

As for a hum or buzz, there are capacitors and coils installed to smooth the 60 hz AC. A call to the vendor might provide insight.
Rick J Fisher, BW is Judy
2007 Alpine 34FDDS Limited SE
2003 Jeep Rubicon or a 1995 Toyota Tacoma
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