My camper has developed sort of a stale smell that was only occurring when I ran the air conditioner. I cleaned the coil and duct work and all parts that contribute to air coming into the cabin, yet the smell was still present, but only when I ran the AC. Finally, I removed one of the ceiling light fixtures and there was a bunch of stale, dusty smelling air coming from the hole in the ceiling for the light. You could feel the air coming out of this hole with the AC running. It's not exactly a mildew smell, more of a stale dust and sawdust smell, which is logical, since there's a ton of sawdust and stuff in the ceiling cavity from the construction of the camper. I have thoroughly checked the camper and there is absolutely no evidence of a leak. Here are my questions...1. I've had the camper for 6 years. Why is this now occurring? 2. Is it normal for some air to be escaping into the ceiling cavity when the AC is running? If not, how do I stop it? I don't want stale air from the ceiling void space to be pumped into the cabin area from all of the light fixtures. 3. Is it possible to seal all of my light fixtures to stop the ceiling space air from getting into the cabin? I thought about installing some sort of vent tube from the roof into just the ceiling cavity that would allow the ceiling void space to vent to the outside. What is everyone's thoughts on this? Thanks.

on the ac units I,ve seen air can not get into the favity, the ac outlet drops down about a half inch below the ceiling, I,d take the cover off outside and inside ,clean with bleach ,clean fan blades to. take a tube od silicone seal and sea around the exhaust box . from your post you might have a little mold growing some where.

might be the rubber seal under the ac, between the ac and the roof. is rotted. last one of those I seen was a pretty cheap gasket.

The plenum of the AC unit is not sealed. There shouldn't be any AC flow into the ceiling space. The gasket between the AC unit and the roof membrane is probably not your problem as it acts as a gasket to seal the weather out of your RV.

midnightsadie wrote:on the ac units I,ve seen air can not get into the favity, the ac outlet drops down about a half inch below the ceiling, I,d take the cover off outside and inside ,clean with bleach ,clean fan blades to. take a tube od silicone seal and sea around the exhaust box . from your post you might have a little mold growing some where.Sounds like the OP is talking about ducted a/c...it may be that a duct has come loose and ids allowing air to escape in the ceiling cavity. Is there a ceiling vent that has little or no air output? I would start there.

Some A/Cs are ducted some are not. Just a hunch but bet they use same A/C for both with ducts on the A/C sealed off for non ducted units. Wonder if those seals may be causing the proble. In any case I would pull the A/C and check gaskets etc.

air from AC escaping into the ceiling cavity | Good Sam Community

midnightsadie
Explorer II
May 05, 2015
on the ac units I,ve seen air can not get into the favity, the ac outlet drops down about a half inch below the ceiling, I,d take the cover off outside and inside ,clean with bleach ,clean fan blades to. take a tube od silicone seal and sea around the exhaust box . from your post you might have a little mold growing some where.
midnightsadie
Explorer II
May 05, 2015
might be the rubber seal under the ac, between the ac and the roof. is rotted. last one of those I seen was a pretty cheap gasket.
westend
Explorer
May 05, 2015
The plenum of the AC unit is not sealed. There shouldn't be any AC flow into the ceiling space. The gasket between the AC unit and the roof membrane is probably not your problem as it acts as a gasket to seal the weather out of your RV.
BurbMan
Explorer II
May 05, 2015
midnightsadie wrote:
on the ac units I,ve seen air can not get into the favity, the ac outlet drops down about a half inch below the ceiling, I,d take the cover off outside and inside ,clean with bleach ,clean fan blades to. take a tube od silicone seal and sea around the exhaust box . from your post you might have a little mold growing some where.

Sounds like the OP is talking about ducted a/c...it may be that a duct has come loose and ids allowing air to escape in the ceiling cavity. Is there a ceiling vent that has little or no air output? I would start there.
WyoTraveler
Explorer
May 05, 2015
Some A/Cs are ducted some are not. Just a hunch but bet they use same A/C for both with ducts on the A/C sealed off for non ducted units. Wonder if those seals may be causing the proble. In any case I would pull the A/C and check gaskets etc.
plasticmaster
Explorer
May 05, 2015
It is ducted AC.
RDMueller
Explorer
May 05, 2015
If you are getting air flow from a ceiling light fixture hole, then air is definitely escaping the ductwork into the ceiling area. Besides the problem of stale air and dust, you are losing much of your cold air into the ceiling, making your a/c less effective. I would start by removing each vent cover and using a mirror and a good flashlight look for any signs of the ductwork being compromised. The ducts are most likely just taped together with duct tape, and over the years, the tape may have deteriorated, combined with the movement of the coach, a connection may have become disconnected.

By looking into the ductwork you may be able to easily find the problem. The bad news is once you find it, the only real option to repair will be to remove part of the ceiling in order to gain access to the area that needs repair. If it were me though, this is something I'd definitely want to fix.
Paul_D_
Explorer
May 06, 2015
The likelihood is very high that the leak is right in the plenum where it leaves the a/c unit as described above or in the shoddy taping job between the duct work and the ceiling vents. Check those places first.
Doug33
Explorer
May 06, 2015
On my A/C ceiling unit, there is a lever that allows either the cooled air flow to come down directly below the unit, or be redirected into the ducted system, or a combination thereof. It's similar to the louvers you have on a car's air vent. Does the A/C unit in question have such a system? It is possible it is directing the air into the ceiling cavity because of a duct issue?
plasticmaster
Explorer
May 06, 2015
No, it only sends the air through the ductwork.