noisy ac unit

[stufisher]

I have a 2017 3790 RD. When the rear ac compressor kicks in it makes a lot of noise in camper. It is still cooling fairly with this new design. The added noise or vibration quietens down with just the fan when compressor kicks out. The unit in bedroom isn't as noticeable. Does anyone know how to silence the added noise or had the same problem. Also noticed that with the ac running the fans won't stay running on low fan, only on high fan when the ac compressor kicks out.
thanks for any ideas

[Jon Susn]

Just bought our first 5th wheel. 2017 Montana 3661RL. I am having a similar problem with the ac in the master bedroom. I have the 30K whisper quite unit ( 15 in Living room and 15 in Master BR). The unit in the BR has a loud rattle, sounds almost like putting a playing card in the spokes of a wheel when I was a kid, but a little deeper. Both units seem to be cooling properly but I have noticed that if you leave them on auto the compressors will cut on and off every minute or so. When I have them on auto with the temp set at 72 they will kick on for about 2 or 3 minutes then kick off for sometimes only 30 to 45 seconds and then kick on again and you can tell that the compressors aren't coming on. Even with my limited knowledge I think that the compressors are cycling too fast. I have to put the AC's on manual/high fan so that they run all the time. This does seem to help with the compressor part of the problem but the noise is constant except for the very first few minutes when you first turn it on.

[DQDick]

With the whisper quiet the cycling you're experiencing is because they are freezing up. Don't know about the excess noise.

[kdeiss]

When the freeze sensor is working correctly it will shut down the compressor fan will continue to run once it senses no frost it will start the compressor .
The sensor is mounted between the fins of the evaporator coil.
Can not explain excesive noise when Compressor is running!

[stufisher]

What causes the compressor to freeze up. In buildings that means freon is low most of time
Thanks

[DQDick]

Actually the same thing happens in buildings also. Low air flow will cause freezing and the Whisper Quiet set up compounds not enough return air space with not enough AC vents and then adds to the problem buy adding a thermostat that runs long periods of time on low fan. Add in the humidity we've had in large parts of the country this summer and you have all you need for a freeze up. Do the same thing in your home and you'll get the same result.

[Jon Susn]

Thanks to everyone for the ideas and suggestions. I will definitely look at the sensors between the coils.

[Jon Susn]

Originally Posted by DQDick

Actually the same thing happens in buildings also. Low air flow will cause freezing and the Whisper Quiet set up compounds not enough return air space with not enough AC vents and then adds to the problem buy adding a thermostat that runs long periods of time on low fan. Add in the humidity we've had in large parts of the country this summer and you have all you need for a freeze up. Do the same thing in your home and you'll get the same result.

DQDick,
I too have already questioned the return air openings in the ceilings. I have two in the living room and 2 in the master bedroom. If you remove the grill like you are going to clean the filter and put your hand inside the area around this I very narrow. I wonder if this is normal or if I just got lucky on this one unit. How would you go about increase the amount of air flow around this vent?

[Denny and Angie Miller]

Originally Posted by Jon Susn

DQDick,
I too have already questioned the return air openings in the ceilings. I have two in the living room and 2 in the master bedroom. If you remove the grill like you are going to clean the filter and put your hand inside the area around this I very narrow. I wonder if this is normal or if I just got lucky on this one unit. How would you go about increase the amount of air flow around this vent?

1 1/4" pvc pipe, cut into ~6" lenghts. hold open the return duct, and then insert the pipe (with the direction of flow obviously). I had major improvement in performance from this, combined with removing every other fin on the supply vent covers

[DQDick]

I used longer pieces of smaller pipe, but the principle is the same. I also left some vents as they come because I wanted to direct the air coming out of them. Downstairs I left the two near the return air intact because they direct the cold air away from the return air, and upstairs I left some to direct the cool air downstairs and also away from the bedroom return airs. The others I cut everyother rib off.

[carrollti]

I am taking mine in tomorrow with the same problem on the downstairs unit. Fan was blowing the other day but compressor never kicked back on, got up to 80 degrees. had to cut the unit off and wait about 20 min then cut it back on. Started to cool then. Still have the bad noise coming out of it.

[Jon Susn]

Originally Posted by carrollti

I am taking mine in tomorrow with the same problem on the downstairs unit. Fan was blowing the other day but compressor never kicked back on, got up to 80 degrees. had to cut the unit off and wait about 20 min then cut it back on. Started to cool then. Still have the bad noise coming out of it.

What model Monty do you have? It would be great if you could post updates on how the trouble shooting goes on this or let the forum know how the problem got corrected. I haven't had an opportunity to implement some of the suggestions from this forum but I will be doing this next week. I pretty sure I will see improvement in air flow with adding the PVC pieces as suggested but am a little concerned over the "clatter noise"
Thanks,
Jon & Susn

[Jon Susn]

Originally Posted by carrollti

I am taking mine in tomorrow with the same problem on the downstairs unit. Fan was blowing the other day but compressor never kicked back on, got up to 80 degrees. had to cut the unit off and wait about 20 min then cut it back on. Started to cool then. Still have the bad noise coming out of it.

carrollti
I just noticed on your profile that you have the same unit as I do. 2017 3661RL. Seems we both are having a noisy A/C issues. I am new to this forum and didn't realize to look at your profile prior to asking you what unit you owned.
I would appreciate hearing the results if any of the noisy A/C
THanks,
Jon Susn

[rslopez65]

We had a noisy vent in the kitchen and it drove us crazy. Your description of the sound was exactly what ours sounded like. Took the vent cover off and found a small piece of what looked like cellophane near the vent opening. Pulled it out and all is now quite thank heavens. Amazing that such a small piece of cellophane could make that much noise.

[Jon Susn]

Thanks rslopez65,
I will have the time and opportunity to check this exact thing out next week.

[twindman]

I have the older A/C units. We came home a few days ago and there was a loud rattle from the A/C. I took off the cover in the ceiling and there is some sort of shroud to direct the air. I think it is on the intake from the room. Anyway, it was a flimsy metal held in place with a hard foam with sticky on the back. It was loose and was vibrating and making the noise. I just pressed it back against the edge of the A/C and the noise went away.
Perhaps you have something similar going on.

[Jon Susn]

I have the whisper quiet. The access to the unit is from the roof. I have not taken the cowlings off yet but I can definitely do that to see if maybe the return air shroud is loose. There may be some type of foreign material stuck inside that the ac fan is hitting on also. Not sure but you can bet that is going to get checked also. Thanks to all for all the ideas and suggestions. This forum surely is great for information about the Montana for a rookie like me.

[kdeiss]

Originally Posted by twindman

I have the older A/C units. We came home a few days ago and there was a loud rattle from the A/C. I took off the cover in the ceiling and there is some sort of shroud to direct the air. I think it is on the intake from the room. Anyway, it was a flimsy metal held in place with a hard foam with sticky on the back. It was loose and was vibrating and making the noise. I just pressed it back against the edge of the A/C and the noise went away.
Perhaps you have something similar going on.

Pickup some Aluminum adhesive duck tape and tape that area that will hold that other foam tape in place

[twindman]

Thanks for info