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Ducted Air Conditioner Dripping into vents?


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Our A/C was dripping into the bedroom vent earlier this summer. We had a mobile RV service blow it out a couple of times (it had been in storage on a farm this past winter and a couple birds built nests in them) and he suggested we run the fan on high 24/7 when it gets over 90 degrees and especially if it is humid.

 

I raised the front end a little bit to assist in draining. Our living room a/c has had no problems since we run the fan all the time but the bedroom is dripping again.

I have little knowledge of the workings of the a/c's and wondering if these 13 year old units, though they do cool, maybe there is a pump or other part that may not be working?

 

Is there something else we should be checking?

 

Thank you.

 

 

 

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Guest THE TRAILERKING

Are they Coleman A/C's?

I doubt if yours has remote drain tubes. Some high-end motorhomes had remote drain tubes go through the roof and down through the structure to the bottom of the motorhome so they didn't slobber all over the roof. Did it used to drip condensate all over the roof previously? If so and it doesn't now, there are slits in the base of the A/C unit close to the roof. Mine did that once and they were blocked with dirt. Cleaned them out and no problem since.

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Are they Coleman A/C's?

I doubt if yours has remote drain tubes. Some high-end motorhomes had remote drain tubes go through the roof and down through the structure to the bottom of the motorhome so they didn't slobber all over the roof. Did it used to drip condensate all over the roof previously? If so and it doesn't now, there are slits in the base of the A/C unit close to the roof. Mine did that once and they were blocked with dirt. Cleaned them out and no problem since.

 

One of my Coleman a/c units was dripping inside a couple of years ago and a repair guy said the drain was plugged. He suggested that he clean it out and drill it a tad larger. I agreed and had him do both of them while he was up there. Not a problem since and I spend my summers on the Florida Gulf Coast where it hot and humid as we all know.

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13 year old unit... Has the evaporator coil ever been cleaned? Are you running the unit on LOW Fan?

 

Run the unit on HIGH Fan.

 

To see if the unit is performing properly, let it run on HIGH fan with the thermostat set lower to keep it running. Take a temperature reading at the air inlet inside and at the air outlet inside with a thermometer. The leaving air should be 18 to 20 degF lower than the inlet. Any lower or higher can be the indication of a problem.

 

DO NOT use an infrared temp gun to measure air. It will only measure the metal or plastic close by which may not be the actual air temperature.

 

Ken

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The repairman took a compressor and "blew out" debris. If debris is in the actual drain piping how would that be cleared?

The problem is that this is only part of the job. The tray should be cleaned and the drain lines flushed. The fact that it did correct the problem demonstrates that he was in the right area, but because he didn't do a complete job the problem has returned. Because the a/c causes moisture to be draining most of the time the unit is in use there will be mold growing in the dirt that has collected in the tray. Very likely the cooling coils are also dirty and probably moldy. With a unit of that age I'd suggest that you have the coils cleaned as that will not only help with this problem but it will also increase the efficiency of the a/c. Once that is done the tray and drains should be cleaned by flushing with a good detergent mix, followed by some type of mold inhibitor or even a mild chlorine bleach/water mixture. If you have one of the small diameter bottle brushes that will go into the drain tube, it would be a good thing to run that through the line.

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Home depot carries an A/C coil cleaner tht is sprayed on/through the coils to remove dust, grease etc. and will not (not supposed to anyway) damage the coils. I have used it on a home unit with good results. Did have to flush out the drain lines it worked so well. :(

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Even with frequent filter cleaning/changes, dust collects on the cooling coil over time and some of that eventually finds its way into the drain pan. If the drain pan is not cleaned on a regular basis, the drain hole will clog and the pan will overflow. In my case, water started dripping out of the bottom of the A/C onto the kitchen counter below. Removing my drain pan for cleaning was not easy and none of the documentation describes how to do it.

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Guest THE TRAILERKING

 

One of my Coleman a/c units was dripping inside a couple of years ago and a repair guy said the drain was plugged. He suggested that he clean it out and drill it a tad larger. I agreed and had him do both of them while he was up there. Not a problem since and I spend my summers on the Florida Gulf Coast where it hot and humid as we all know.

Mine have small slits/slots in the bottom of the pan.

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We have the dripping problem as well.

The solution that removed 95% of the problem was clearing out the mud daber nests from over the top of the drain areas. We have to remove ll of the internal covers to find them all. If it rains we still have a small problem but I haven'v cleaned out the coils yet.

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The dripping from rain is from the four main bolts having loosened up. The only seal from outside is a foam rubber gasket that is 14" square and sits between your roof and the A/C. They are not glued down although it does have sticky to keep it in place and not sliding around when putting the A/C on top.

 

The foam gasket is commonly called a rubber donut. when installing a new one or having a bit of a leak from an old one only during rain the problem are the nuts on the mounting bolts that you can find under the faceplate inside the rig. They loosen over time causing a leak during rains.

 

There is a trick to tightening them as they not only seal out rain and condensate, but they isolate the unit from all the vibrations of the A/C. So if you tighten them down too much the vibration noise increases. Too little and it leaks. Most manuals say to tighten the A/C mounting bolts so that the gasket is compressed to about 1/2" or so. But check that for your model. Many times just snugging down an otherwise good gasket will stop the leaks in rain.

 

If the leaks continue you will need to get up on the roof with help and a big three by three foot piece of plywood or heavy cardboard to set the A/C unit on while replacing the donut, so the roof membrane or material is not damaged by the metal A/C base. Then put the new one on the A/C with the stickum or on the roof so it won't slide around and have another third party inside to tell you when it is square in the 14" opening.

 

You need to take the plastic cover off and the plenum or bottom enough to be able to see the evaporation or cooling coils. If the dripping when on and not raining continues with poor humid cooling odds are the coils are freezing up. And you can see the ice covering them.

 

If it is icing up it is usually from too little refrigerant or if it starts icing up immediately after charging, the same icing can happen with too much refrigerant.

 

I was in my mid 40's when we retired and took to the road, and I would scramble up the ladder like a monkey at 45. Now at 63 I drag my but up one rung at a time and make sure I have the SH home to call an ambulance if I fall off!

 

I was just up there yesterday and cleaned/hosed out the condenser coil, all the accumulated dirt, insects and nests, and cleaned the green A/C shroud only to find it became white and just like new with a bit of scrubbing. Now I did shoot a brief stream of water in the condensate exit gutter and as expected had a few drops of water on the vinyl flooring from that just to break loose anything that has been sitting there like a dirt dauber nest.

 

That's really all there is to leaks with the A/C.

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My bedroom unit drips out the grill when it is raining. I have removed the cover and there is no debris in the unit and the drains are open. It is all sealed properly.

That probably either means that you need to tighten the hold-down bolts (4 on most RV a/c units) or you need to replace the foam gaskets that seal the opening to prevent moisture entering. Replacement isn't difficult but lifting the a/c can be. It is generally a two person job if you do this yourself.

 

Does it drip even if the a/c is not running? If it only does so when air conditioning in rainy weather but not when the a/c is shut down, there must be some problem with rain getting into the coil area or the drains are not completely clear.

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Kirk it is not dripping from the gasket. It is internal to the unit itself. It is up where the styrofoam is. I believe it is due to all the moisture being taken out of the air. As Jim posted I guess I need to take off the covers under the outer covers and see what I can find.

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AS noted earlier, be sure that the outlet side of the blower is not leaking into the inlet side. Use the aluminum tape on any suspicious areas. Be sure and wipe the area down to get dust off so the tape will stick.

 

Did you check the temps across the unit and get a 20 degF spread?

 

When you go up top and pull the sheet metal panels check the evaporator coil for cleanness. Be sure and seal the seams with the aluminum tape to prevent air leaks.

 

Ken

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  • 1 month later...

FYI,

 

IF you have a ducted system and clearing the drains doesn't solve the problem.....I read on another forum that Dometic suggests installing additional vents on the return side of the system. In theory ducted systems equally distribute the conditioned air: one row is the supply (or exhaust) side and the other is the return (or intake) side. The way to identify the return duct is the one with the foam filters. Dometic suggests that the return have an unrestricted supply of air. Adding two or three more vents on the return side only will solve the problem.

 

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