2018 19FBS with almost useless AC

CPC659 · 04-01-2019, 10:10 PM

We realized this weekend the AC unit has no AUTO setting. Here on the muggy, muggy Gulf of Mexico, besides making it cooler, the AC is what we were planning to use to deal with the heavy humidity. In Galveston last week the humidity was over 85%. It read 82% at one point inside. The AC brought it down to almost 50% in minutes. All good. Then the fan kicked on and sucked in all that moisture all over again. Back up to 80% in minutes. I had to get up and shut off the fan. Now that's just an inconvenience. When we're awake. But I can't get any sleep if I have to get up every time the fan comes on so that would mean no AC at all when we go to bed. Just not an option for most of the year here. I'm stumped. Am I going to have to replace the AC on a unit we bought just 4 months ago?

Witch Doctor · 04-02-2019, 01:14 AM

What fan you talking about that sucked in outside air if I read that right?

tc cruiser · 04-02-2019, 05:53 AM

CPC
Wow, I live up north and don't really use the A/C but may someday need it and was hoping it would do its job.
I thought the A/C doesn't cool the outside air. I should just recirculate the air in the trailer, am I correct?
I'm gonna follow this post and see how this plays out for you. Did you talk to your dealer about this yet?
TC

cavie · 04-02-2019, 06:59 AM

You have it all wrong. Your A/C does not can not bring in outside air. It recirculates only inside air just like any residential AC unit. Your T-stat does have a fan control. Fan on/fan Auto. Maybe fan high and low also. With the fan set on Auto it will come on and off with the compressor and give you some quit time between cycles. Fan on will leave the fans running at all times while the compressor cycles on and off.

If your fan shut off then it was in the Auto mode. It will come back on when the compressor come back on. You can even run the fan without the compressor running just for circulation.

TheWolfPaq82 · 04-02-2019, 07:07 AM

Quote:

Originally Posted by cavie

You have it all wrong. Your A/C does not can not bring in outside air. It recirculates only inside air just like any residential AC unit. Your T-stat does have a fan control. Fan on/fan Auto. Maybe fan high and low also. With the fan set on Auto it will come on and off with the compressor and give you some quit time between cycles. Fan on will leave the fans running at all times while the compressor cycles on and off.

If your fan shut off then it was in the Auto mode. It will come back on when the compressor come back on. You can even run the fan without the compressor running just for circulation.

X2

tc cruiser · 04-02-2019, 07:31 AM

CAvie and Wolfie
Our thermostat on the 19 fbs seems to be the most basic available. I believe the A/C is just operated by knobs on the unit it self.
If I remember correctly we have something like this in our trailer.
https://www.ebay.com/itm/Dometic-RV-...-/123676155257

Again, I only tried my unit one time to make sure it cooled and worked. I don't think I even touched this thermostat to operate it.
TC

**KyDan** · 04-02-2019, 07:36 AM

We're trying to help but just guessing until you tell us the make and model of your AC.

tc cruiser · 04-02-2019, 08:00 AM

I just dug through my paperwork and it is a coleman mach low profile 13.5 k btu model 47253B879 and you operate it with 2 twist knobs on the ceiling . This seems to operate like a standard window unit in a home.

5picker · 04-02-2019, 08:07 AM

Quote:

Originally Posted by tc cruiser

I just dug through my paperwork and it is a coleman mach low profile 13.5 k btu model 47253B879 and you operate it with 2 twist knobs on the ceiling . This seems to operate like a standard window unit in a home.

I had a SOB (some other brand) that had the basic, knob controlled A/C and it had no Auto setting.

But, even when operated by knobs in the unit, the A/C does not suck in air from the outside.

It simply recirculates the inside air in the R/V, even if the fan runs constantly or cycles, it isn't going to bring in any outside air.

**Mr. Dan** · 04-02-2019, 08:27 AM

OP CPC659, can you respond to any comments here so we can help with your original problem?

formerFR · 04-02-2019, 08:29 AM

I don't know of any 'air conditioner' that operates without it's Fan on FIRST, then the compressor(cold air) kicks on... the fan will ALWAYS be on when the compressor is on.
The compressor relies on the fan to move air across/thru the unit...

Maybe the OP is referring to when the fan speed changes from Low to High...

There are times when the compressor will turn off, yet the Fan will still be running... this could result in 'warmer' air flowing thru the system, as it then is simply moving air around the RV.

Witch Doctor · 04-02-2019, 08:30 AM

TC, what are you using to measure the humidity? For one thing, the humidity will start to rebuild as soon as the A.C. shuts down from reaching temp, when the unit comes back on your going to feel air movement across your skin. You might not notice it sleeping until the unit comes back on. It's the same if you had a dehumidifier and it shut off. Humidity is in your furniture, rugs ,walls and everything else. If your pulling in outside air you need to check that. You would have a leak which is possible, but they are not designed to mix ambulant air with conditioned air, only commercial units do that, because of health requirements. So I can't doubt what you say but if this is true, get it checked. In high humidity it is best to leave the fan in the on position so it is constant. The compressor will cycle as needed, but with the fan it will feel better inside with the movement.

CPC659 · 04-02-2019, 08:30 AM

Someone else on another page just stated the same about not drawing from the outside air. I am using a humidity gauge in the trailer. I even check it a few times a week when stored. I am not simply guessing at the % of humidity. When the fan starts to run the humidity rises rapidly. I can guess that is because outside air is being drawn in. Circulating the air would not cause that.

cavie · 04-02-2019, 08:36 AM

Quote:

Originally Posted by tc cruiser

CAvie and Wolfie
Our thermostat on the 19 fbs seems to be the most basic available. I believe the A/C is just operated by knobs on the unit it self.
If I remember correctly we have something like this in our trailer.
https://www.ebay.com/itm/Dometic-RV-...-/123676155257

Again, I only tried my unit one time to make sure it cooled and worked. I don't think I even touched this thermostat to operate it.
TC

That t-stat is for heat only. Your controls for AC are on the AC itself. The same rules apply. No outside air circulated. Think of your AC as a motel unit.

Witch Doctor · 04-02-2019, 08:45 AM

Quote:

Originally Posted by CPC659

Someone else on another page just stated the same about not drawing from the outside air. I am using a humidity gauge in the trailer. I even check it a few times a week when stored. I am not simply guessing at the % of humidity. When the fan starts to run the humidity rises rapidly. I can guess that is because outside air is being drawn in. Circulating the air would not cause that.

That is because it is cirulateing air in the unit, the RA is sucking the humidity out, and the evap coil is changing the state to water , that's your condensation. If this is bothering you so much, look into a potable dehumidifier and let it run 24/7. You can only do so much, this is a trailer which is not air tight. Good luck and stay dry

Witch Doctor · 04-02-2019, 08:53 AM

Also don't put all your eggs in one basket, it has been my experience that humidity gauges do not change that fast. People in the business "air balance" people use a wet bulb, and a sling to get a accurate reading and that still takes time for movement.

rockfordroo · 04-02-2019, 09:02 AM

Although most AC units recirculate inside air, "most" hotel type units also have a vent that can be opened/closed so you pull in about 10% outside air. You car is the same (when you push the "recirculate" button, it closes the outside vent).

That being said, I've had the cover off of my AC and don't recall seeing any kind of outside vent, certainly not one you could control, but on the other hand, I wouldn't say it was hermetically sealed, either.

What I think the OP is seeing, perhaps, is that the AC is bringing down the humidity at his humidity gauge, but not necessarily throughout the rig. I'm guessing the AC would need to run/cycle for some time, maybe a couple hours, in order to get the humidity down throughout the rig, especially if his humidity gauge is more or less under the AC's discharge.

CPC659 · 04-02-2019, 09:12 AM

Quote:

Originally Posted by rockfordroo

Although most AC units recirculate inside air, "most" hotel type units also have a vent that can be opened/closed so you pull in about 10% outside air. You car is the same (when you push the "recirculate" button, it closes the outside vent).

That being said, I've had the cover off of my AC and don't recall seeing any kind of outside vent, certainly not one you could control, but on the other hand, I wouldn't say it was hermetically sealed, either.

What I think the OP is seeing, perhaps, is that the AC is bringing down the humidity at his humidity gauge, but not necessarily throughout the rig. I'm guessing the AC would need to run/cycle for some time, maybe a couple hours, in order to get the humidity down throughout the rig, especially if his humidity gauge is more or less under the AC's discharge.

THIS may be the issue. Now that I think about it, it was within feet of the discharge. (well...everything is within feet in this tiny thing, LOL) Next time I'll place it as far away as possible from the unit itself. Either in the above bed storage or attached to the microwave.

jeff64 · 04-02-2019, 09:43 AM

What everybody is telling you is pretty much the straight skinny on this. Might add that if you compare inlet air temp to outlet air temps there won't be much more than 20-23 degrees difference if everything is right. Dehumidifiers, circulating fans and one of the foam type pillows in your roof vent will help. There were threads a while back on optimizing the ducted ACs with foil tape, which works. Don't have a feel how that would work with your configuration. Do a search on AC mods at top of page or appliances on home page

cavie · 04-02-2019, 11:23 AM

Quote:

Originally Posted by CPC659

Someone else on another page just stated the same about not drawing from the outside air. I am using a humidity gauge in the trailer. I even check it a few times a week when stored. I am not simply guessing at the % of humidity. When the fan starts to run the humidity rises rapidly. I can guess that is because outside air is being drawn in. Circulating the air would not cause that.

Pay attention. You can not draw outside air inside. If you are, get on the roof and remove the cover and find out WHY!

OR you have a window or roof vent open.

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