Vibration and Hum

[Will Garner]

Two weeks ago while camping in Bryson City, NC we were surprised by an unannounced start of a hum accompanied by a vibration. Both seemed to be centered around or under the galley area. We looked under the cabinets and found nothing. We looked in some of the underbays where the vibration and hum seemed strongest/loudest. Including the third bay driver's side (water heaters/LP tank; fourth bay driver's side (plumbing gray/black tanks), second bay curbside (house batteries/inverter), and third bay curbside Cruiseaire and battery chargers/converters - 2). All to no avail.

On Saturday I even took apart three of the bays hoping to find something hidden that was the culprit. Nope not happening.

Now these symptoms were/are present when hooked to shore power, when not hooked to shore power but on generator, and not on generator or shore power but on the inverter. In fact the only way I was able to get them stopped was to place the overhead toggle in the panel in front of the passenger seat for the "Domestic Battery Disconnect" switch in the off position. Kills power in the coach.

The symptoms have now morph'd from being constant, where someone with more savvy than me could diagnose it, to being random and intermittent. Of course when at Carolina Coach in Claremont NC (off I-40 exit 135) on that Monday to get it diagnosed it would not cooperate. Carolina Coach in fact decided they were not "qualified" to work on a Prevost. I tried to tell them they were working on the Country Coach systems, the systems just happened to be wrapped inside a Prevost instead of a plastic coach. No luck.

On Friday last week I took it to Hawley's Camping in Fayetteville, about 45 miles from home. They were willing to work on it but you guessed it, the gremlins would not come out to play that day. Of course once back home and parked at the curb in front of the house for about two hours, the gremlins were back in full force. Carole actually asked me if I had left the generator on - no I hadn't.

So anyone out there with a 1990-1991 vintage Country Coach - have you ever run into this condition? How about some suggestions of what to try or where to look that I have not already tried. I may have to go to Buddy Greegg's in Knoxville, TN to get it fixed.

Thanks in advance for any and all information and suggestions.

Will

[garyde]

I have had two different . One was my outside small refigerator, the motor was going bad and finally died. The other was a fan in the inverter bay, it was going bad and intermittantly would stop.

[Coloradobus]

I agree with Gary,
That was my first thought, Inverter cooling fan. Our's are hard wiried to the house batteries. Other than cutting the house power, they are always on.

[Petervs]

I also vote for inverter cooling fan. They might only come on if there is heat being generated by the inverter, controlled by a thermostat.

[Jon Wehrenberg]

If Will had his head in the bay where the inverters are and he was unable to pinpoint it I suspect it is not one of those little inverter fans.

I also suspect his coach is not as it was built by CC. I suspect it has been modified so it makes diagnosis more difficult. Things that come to mind are a constantly running water pump. One other CC owner with the same vintage coach had this problem. It could be the coil in a large relay making the noise. Some coaches of that vintage had a coolant circulating pump as part of the house and coach heating system. That's a stretch, but on my 87 I had one and when it was functioning it had a distinct hum. Could it be an aux air compressor? That vintage coach had converters that functioned as battery chargers, but also allowed the batteries to be turned off and they provided 12VDC for lighting and other purposes. Those converters made a loud hum.

Bringing the coach to Buddy Gregg's or anybody else isn't going to help because the techs that look for the noise (at $100 per hour) aren't going to do any more than Will can do. They are going to listen to try to oin point it and start removing panels and opening doors until they can isolate the noise.

[sawdust_128]

You live in Southern Pines. still very warm. This started in Bryson City, getting colder this time of year? Could it be heating systems (e.g., circulator pumps or fans)or bay heaters?

[mike kerley]

Our 93 CC has an aux air pump located behind a small door on the rear side of the first compartment. Its behind the generator and next to the generator battery. It hums when running. You should have a shut off switch in that same first bay. See if turning off the aux compressor silences it.

[gmcbuffalo]

I have a 91 Beaver conversion and it has two water pumps, if the pressures sometimes gets out of sync and one will run forever and make noise. When you hear the noise turn off the water pumps and see if the noise goes away. There a screw on the controller for each pump that can be adjusted to get them to turn off together.
GregM

[Will Garner]

Mike,

First, I want to thank everyone that pitched in to provide advice on where to look for my problem. Mike Kerley is the winner. I had forgotten all about the toggle below the eletrical panel on the driver's side front. Carole and I were in Boone NC for the weekend. We took our laptop on this trip. I checked the posts on Saturday evening and Mike Kerley hit a home run (or scored a touchdown) with his piece of advice regarding the toggle switch. I went outside, opened the access door, turned the toggle switch to the off position and yeah it went quiet! So now I know where to start looking for the Auxilliary compressor which is now most likely the source of the vibration and hum. I just hope it is not the compressor driven by the engine as I believe it is in a place I can't physically bend myself to get at (near the power steering pump). I'll start where Mike suggested, in the access panel to the generator battery.

It will be the end of the week before I can start taking things apart to see if I can identify the compressor location. I think this winter will be a season of doing upgrades on some other things too so I don't have more surprises.

[mike kerley]

Will, I replaced my Aux compressor a couple of years ago with a unit ordered from Granger. Cheaper than CC, but still more than others have paid from other sources. They can also be rebuilt if the compressor is failing.

Our 93 has an "auto level" feature which levels the coach on the air bags when parked. When the bags were leaking, our aux compressor would run frequently which caused the pump to fail. With the new air bags, the pump will run once a day in warm weather, maybe twice a day when its cool our(no cold weather allowed here).

Mike

[Jon Wehrenberg]

The best thing anybody can do to prolong the life of the aux compressor is eliminate the leaks. I know of none that have severe duty or continuous duty ratings.

We had the automatic leveling feature in our 87, and found out that a windy night would rock the coach enough to drive the system crazy. We stopped using it after that and just manually leveled the coach and shut it off.

[Jerry Winchester]

We had the automatic leveling feature in our 87, and found out that a windy night would rock the coach enough to drive the system crazy

Yep I'll bet it was the wind. :eek:

[tdelorme]

Come on, Jerry, let ole Jon brag a little bit. :o

[Jon Wehrenberg]

If anybody knows about wind it has to be JDUB.