Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 14, 2025 ...

Buzzing

March 23, 2013, 05:33:32 pm

We have a loud buzzing coming from one or both of the two black boxes shown in these two pictures. This happens only when we are plugged into shore power, or at least we can hear it then. The buzzing is loud enough to be heard in the coach. I'm assuming that these are for charging the batteries.

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Re: Buzzing

Reply #1 – March 23, 2013, 06:01:18 pm

AC hum type, might be dirty contacts / seating of poles on th normal line 50 amp contacor.

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Reply #2 – March 23, 2013, 06:15:21 pm

These are old convertors.  It's time to upgrade to modern three stage inverters.

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Reply #3 – March 23, 2013, 07:32:17 pm

It appears that there has been little, if any, upgrading done to this coach. There is a 1500 watt Taytronics inverter, too. I wonder if that needs to be replaced soon, too.

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Reply #4 – March 23, 2013, 09:29:45 pm

I learned something. I do not know as much about the pre 96 units as I have not owned one but I did learn from your post and the answers.

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Reply #5 – March 23, 2013, 09:58:24 pm

I don't know much about any of them except that Foretravels seem to be very well built. When we bought this coach we knew we were getting a lot of 20-year-old stuff that would need to be replaced. Fortunately for us, there are lots of very generous people here who gladly share their knowledge with those of us who don't know what that buzzing black box does.

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Reply #6 – March 23, 2013, 10:40:59 pm

They do look like converters but appear different from what was originally in my '91.  Mine was in the utility bay mounted to ceiling and only a single unit (house).  The braided 12 volt  cables look exactly what was on my coach.  Since there are two maybe one is for the house and the other for the chassis?  It looks like it was done by the factory.  There should be a breaker under the bed that is dedicated to the converter.  You could throw that breaker to see if the buzzing stops to confirm.  Transfer switches are know to buzz too per Dave M's comment - I had one that was really loud.
As far as replacing your old Taytronics, if it's still working you might want to keep it if you're not planning on boondocking much.  "Kenhat" still has his and there was this recent thread on the subject: Problem with GFI circuit
You probably already know, but if you decide to get rid of the Taytronics you'll want to get a inverter/charger unit so you can dump the converters or keep them as backups (but unplugged).  Whole bunch of different ways to add in a new inverter - all depending on how you want to use it, how much work you want to put into it and how much money to spend.

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Reply #7 – March 23, 2013, 10:47:42 pm

David,

I think, as Brett said, that black box is a converter, which means that it converts 110AC to 12 V DC for your coach needs (12 V lights, fans, furnace blowers, etc). The previous owner of my coach replaced that box with an Iota 55 amp converter/3 stage charger and kept the Taytronics 1500W inverter (transforms 12V battery power to 110V AC). I still have the Taytronics, as it works fine for limited AC needs. If you ever wanted to switch to a residential fridge you would have to upgrade to a larger inverter.

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Reply #8 – March 24, 2013, 07:59:56 am

Given that the refrigerator doesn't seem to work (it did when we first saw the coach, but wasn't when we went to get it), I'll probably need to do some planning here for replacing the inverter and converters, refrigerator, and tires. I'll start a new thread on that project this afternoon.

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Reply #9 – March 24, 2013, 09:24:11 am

David, What you have are a pair of converters that put out about 50 amp of DC power. When you have plenty of shore power, they will put out close to 100 amps when the batteries are down. When you have very limited shore power, example 20 amp out of a friends house,You can unplug one of them and still keep the batteries charged while you live in the coach. The humming noise is normal and will usually be louder when the batteries are low.
  The inverter has limited use and is totally obsolete.  You could replace both systems with a new inverter charger system BUT,,that will also need a larger bank of house batteries and a place to put them.
 Gary O

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Reply #10 – March 24, 2013, 10:14:34 am

Not mentioned but seen in the photo is the white fiberglass removable cover. 

Behind my cover are the connection for the batteries, circuit breakers, and two fuse blocks.  You need to remove the nuts and the cover and discover what is being hidden.  I have labeled the cover with stickers telling me what fused items are protected.  In addition one of the circuit breakers is mounted so that from the next compartment, I can stick a finger thru the wall to reset the breaker.  Surely not something you find unless you know the set up.

No telling on your coach what you might find.

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Reply #11 – March 24, 2013, 12:00:37 pm

Neither of my 93's had this setup. I have to agree with others that at least a smart chager/converter should be added. Mine is wall mounted in the bay behind the generator bay. Luckily the previous owner opted for a Xantrex 3000 Invert/Converter/Charger. I had installed a 90 amp, Iota smart charger/converter from BestConverters.com in my 93 U225 just before Dave Cobb bought it. It was installed under the step accessed by the bay door on the drivers side.

As Dave M said, the buzzing is usually dirty or pitted contact points on either the Automatic Transfer Switches, the Converter switch or the Electrical Protection (EMS) switch if it has one. The all have points that will vibrate if a solid connection is prevented by dust, debris or damage. They a are usually easy to fix by filing or sanding the point surface once you make sure all and I mean all power is off to the coach. Don't ever forget the inverter when working on the electrical. After unplugging shore power, remove the battery cables on all the batteries just to make sure. 

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Reply #12 – March 24, 2013, 02:38:04 pm

"After unplugging shore power, remove the battery cables on all the batteries just to make sure." That's a habit I got into many years ago. If I can't make sure that the cables can't get back to the battery I'll tape the cables so even if they touch the batter they won't make contact. I also remove my wedding ring (my watch died years ago and I never replaced it). Then, when I'm about ready to start poking at stuff I sometimes jump from whatever I'm about to work on to ground just to be sure.

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