Mystery Noise

[Bill Heffernan]

We have been full timing in our rig for several months. Over the last two nights we have been hearing a mystery noise. There is a system cycling that  appears to be coming from underneath the bathroom. It runs for 10-20 seconds every 30 minutes or so. I thought it was the water pump, but have confirmed that it is something else. Any ideas as to what we are hearing and why this system is suddenly running. It has been colder the last 2 nights - down close to freezing. It is disrupting my beauty sleep -  .

[Eric Maclean]

Bill
It is likely the tank bay heat exchanger kicking in to maintain the tank bay temperature they are usually set at or around 40 degrees .you properly can't see the unit as they are in the closed section of the black / grey water tank bay but any noise that they make would be below the bathroom area usually.

Hope this helps
Eric

[Joel Ashley]

I’d guess Eric is right, but I’d think a heat exchanger would run more than 20 seconds.  If it’s near its thermostat and in a confined bay such as in our black tank bay, perhaps 20 seconds is enough to reach the thermostat’s prescribed 40+ degree F set point.

Another device that can display what you describe is the auxiliary compressor.  The HWH Auto-level system awakens every 30 mins. (if memory serves me right) to check a parked coach’s balance.  If it’s out of whack the system kicks on the compressor to pump up the sunk bag(s).  I have often noticed ours coming on evenings when we just move around inside, our relatively minor weight shift being enough to change the relationship between bags.  It’s usually not really a sunken bag, but simply the difference in weight distribution between when the auto system was set or the last adjustment and the weight shift.  It then usually only runs for 10 seconds or so.

But because the auxiliary compressor is commonly located under the entry stairs, Eric’s suggestion seems a more plausible culprit.

Joel

[Eric Maclean]

Joel
You just reminded me of an other device that may be making the noise in that area the inverters cooling fan with sometimes cycle for short periods depending on load in my coach the inverter is hung between the frame rails just on front of the the tank bay way in the rear most storage bay. That one you should be able to get close enough to pin point the noise.

Eric

[Bill Heffernan]

Thanks for the responses. I think Eric is correct on the heat exchanger. As I mentioned it has been down close to freezing the past couple of nights, but it has been close to 70 during the day and the sound goes away - the sound has to be the heat exchanger. Thanks as always to everyone for the insight!!!

[Joel Ashley]

Some sounds on these rigs just take getting used to, Bill.  You can expect to hear that exchanger throughout the cool seasons.  It’s thermostat, separate from your living area ones, is preset at 40-42F so your tanks and water lines in the basement don’t suffer freeze damage.  The susceptible bays are usually linked by airways so they all benefit from the exchanger.  Our water tank, though some distance from the exchanger, is right next to the HydroHot, which as long as it’s on to heat the coach and provide hot water will by convection keep the tank from freezing.

Now as to beauty sleep, you can come get the ornery neighbor’s new and illegal rooster whose pen is 16 feet from our bedroom  .  Some sounds shouldn’t require getting used to.  Fortunately, some mitigation is provided by Monty Rae, parked between.

Joel

[Bill Heffernan]

Thanks   

[Joel Ashley]

My waste tank bay:

[Keith Moffett]

Bill
The auxiliary compressor on ours is mounted just ahead of the drive axle on a platform.   When needed it will run 10 to 30 seconds.  Sounds like your culprit.  If yours is located like mine you will see it with a flashlight just ahead of the drive wheels about half way across underneath.

[Bill Heffernan]

That's it. Thanks