Dometic AC Smoke and Roof Leak

One year of ownership...one week past the warranty date.  One roof leak, passenger side at the seam between the transition and the coach side wall.  I've done the search on the site and found a few threads.  Going to look over the vertical and horizontal seams along with the marker light and awning wiring grommet. 

The one that was more concerning was the smoke from the front AC unit.  It was smelling a little starting two days ago.  Slight 'hot plastic' smell but my wife didn't smell anything.  Covid did a number on my sense of smell so I can't trust anything in that department.  Got worse this morning when packing up to leave the camp site, and there was a slight smoke haze.  At first thought it was a wild fire that was south of where we were at but I went outside and there was nothing.  Realized it was the front AC unit and shut it off.  Going to see if it is a bad wiring connection for the incoming power.  I've read on the interwebz that has happened to folks; loose connection leading to higher resistance and resulting heat / melted or burned wire insulation.

Anyone else deal with something like this?  Not sure if the wiring connection is accessed from the inside or on top.

In all my years on this and other forums, I never read of an a/c developing smoke from a burn of some sort with the potential of catching on fire.  That is surely a serious matter.

I would call the factory and see if they will stretch their warranty an extra week.

I agree with Ron, I too have never heard of a smoking A/C unit.

DO not use that A/C, get a professional to find out what's up with that.  The leaking should be a simple fix.

I too would call the factory.  The a/c isn't warranted by the factory, that'd the a/c mfgr's warranty.

Pulled the inside cover / air distribution panel plus a small plastic access panel inside that.  Note there are six (6) screws holding on the cover.  The coach to Dometic wiring can be accessed from inside and it uses plug connecting the two and not a terminal block (pictures forthcoming).  No visible issues.  No crispy or charred wire insulation.  Nothing out of the ordinary.

We decided to get a mobile mechanical out to pull the cover on the roof.  You can't see any of the Dometic side of the wiring from inside.  Whatever is found, we'll pull the cover on the 2nd unit to check it as well even though that unit was running fine with no issues.

If you do an internet search, you do see a few posts from different RVs (coach and trailer type) where smoke develops on rooftop AC units due to a loose connection causing some resistance at a connection where there would normally be none.  That or an overheated motor are the only things I could think of that would cause the issue.  The coach side wiring was fine.  The unit was cooling at the time it was shut down.

And no we won't be using the unit until the issue is solved.  And yes I killed power at the breaker AND disconnected from shore power as a just in case before I stuck my hand into the bundle of wiring inside the unit.  Last thing I needed was to touch a bare piece of wire where the insulation burned off.

While the mobile mechanical is around, I'm going to pick his brain on the water leak issue.  Get a second set of eyes on the seams.  I'll do the sealing and the water testing with a hose.

Glad you are "on" the a/c smoke situation.

About the water leak near the entry door forward, there was a history of postings of water getting inside right where you describe.  You already mentioned this, but I "emphasis" it.  Look first where the wiring to the automatic awning passes through outside-to-inside.  That is the most logical place to start your investigation as well as inspecting the exterior sealant where seamwork is located.

Water intrusion on PC's had always been a very rare complaint, that is until the electric awning was introduced.  Admittedly, I have not heard about it for some time, assuming Phoenix has since applied extra care to that vulnerable area.

Inspect the radiused edges of the fiberglass roof, where it goes underneath the front cap. The gaps are about .25” at the ends of the seam, so check there first for voids in the caulking.


If you have the Dometic a/c’s, the exterior shroud is fastened on by 4 torx screws. That’s simple to remove if you just want to check for any visible  signs of  damage.

I noticed a water stain on my PC inside wall when I bought it (10 y.o. at the time). It was impossible to tell how old the mark was, but I tracked it to the wires for the awning. So,,, I sealed it up inside and out with butyl & dicor.  I made sure that the wires on the outside led down and away from the hole so that water didn't run down them TO the hole. I've never seen any indicators of it leaking since.


I also got the water stain off with some diluted oxiclean.


Larry

Thanks for the replies on the leak.  I'll look those areas over for the leaks.  I did some thread reading on this forum and looking at getting some products gathered to seal things up as I find them.  What did folks use for the vertical and horizontal seams on the sides of the coach?  3M 5200, Dicore lap sealant or other?  Assuming for any seams on the roof the Dicore lap sealant would be the product of choice.

For the Dometic rooftop, I'm avoiding getting on a ladder this week.  Back is acting up and I have a service week next week so I'm trying to get well enough to work on a senior's home with the church.  Biting the bullet and getting a mobile mechanic involved to avoid too much downtime during the RV season.  We're already losing at least one of our weekend trips.

First get your ACs model and serial number and call Dometic and get info on the individual manufacturer warranty and their repair policies. It's longer then the Phoenix Cruiser warranty.  Dometic RV air conditioners may come with a warranty that lasts two to three years from the original purchase date.

The only thing that could cause your AC to smell like smoke is a failed/failing fan motor. The same motor turns the fan for the condenser and for circulating the interior air thru the evaporator coils. So it has a shaft on both ends.  If the warranty doesn't cover it a new fan motor is about $100-$200 or less depending on the model. They are usually available on Amazon. If your an DIYer its a fairly simple fix if your comfortable getting up on your roof. If you have never done it before it will only take about 2 hours  I'd recommend also ordering a condenser, fan blade and cleaning out your condenser coils. I was not an expert but just followed YouTube videos to learn what to do. If you have it done the usually labor is around $500 and you can get really price gouged by unscrupulous dealers/techs. BUT the other issue is getting it scheduled in to be repaired.

Thanks for the info.  I wasn't aware of the dual shaft motor running both fans.  Normally I'd get on the roof but still battling a bad back, so I'm getting a mobile tech on Saturday to take a look up top.  The fan motor is on the list of suspects.

First get your ACs model and serial number and call Dometic and get info on the individual manufacturer warranty and their repair policies. It's longer then the Phoenix Cruiser warranty.  Dometic RV air conditioners may come with a warranty that lasts two to three years from the original purchase date.

The only thing that could cause your AC to smell like smoke is a failed/failing fan motor. The same motor turns the fan for the condenser and for circulating the interior air thru the evaporator coils. So it has a shaft on both ends.  If the warranty doesn't cover it a new fan motor is about $100-$200 or less depending on the model. They are usually available on Amazon. If your an DIYer its a fairly simple fix if your comfortable getting up on your roof. If you have never done it before it will only take about 2 hours  I'd recommend also ordering a condenser, fan blade and cleaning out your condenser coils. I was not an expert but just followed YouTube videos to learn what to do. If you have it done the usually labor is around $500 and you can get really price gouged by unscrupulous dealers/techs. BUT the other issue is getting it scheduled in to be repaired.

The Dometic compressor motor and fan (inside air blower) are two different motors.

Just listen to it when you first turn it on.  The fan will run blowing the air and the 30 seconds or so and you can hear the compressor turn on.  As the a/c runs, you can hear the fan speed go up or down and the compressor turn on and off.

I installed a Soft Start on my a/c.  The compressor motor is inside a sealed unit that is above the roof.

This was on a Dometic Penguin II.

I don't think you would need a condenser (the freon coils on the cold side) unless they prove to have a leak. However I would agree on the cleaning. I'm always surprised how dirty my coils (evap & condens) get in 12 months. After cleaning, airflow is better and I feel like they are quieter.


But,,, I agree on the likelihood that the fan motor is the source of the smell.


Larry

Update - had a mobile technician stop by our storage place and take a look.  BTW, mobile is the way we're going to go from now on.  So much nicer to know that when they show up that you get your rig looked at vs dropping off and maybe they look at it sometime in the next week.

Anyway.  Pulled the outside cover and took a look inside for the front unit.  No signs of wiring issues or charring.  Cranked up the genset and ran the unit.  Current for fan motor and compressor spot on. Nothing out of the ordinary and no smell coming from the unit.  Pulled the cover on the back unit and everything looked good there as well.  He asked what else was running and I said the rear exhaust fan, so he had me power it up and checked current on that fan as well.  Nothing.  After he left I ran the unit on generator for a while and everything was normal.  Cooled and no issues.  We'll continue to keep an eye on it.  I suspect the fan motor may be the culprit but no smoking gun to point to (pun intended).  We won't run the front unit unless we're there and awake.

For the water leak, he look at all the seams and only found one spot on the U shaped vertical seam cover that was pulled away a small amount right at the corner of the roof.  He sealed that and the wiring entry for the awning.  Nothing else looked suspect.  He did a general review of the whole roof and it all looked good.  We'll keep a close eye on the area as we get out and about.  Thankfully we have enclosed storage so we'll be present when its out in the rain.

Minor update - we pulled the RV out so I could put my trailer back into storage.  While out, we cranked up the genset and ran the front AC for about 30 min while we pulled around to the local water source.  Used the hose to douse the upper corner area including the upper portion of the awning support.  No leaks seen and no issues with the AC.  We're forging ahead with the RV season and will keep tabs on these items.