Our 2015 FCFB25 trailer came with an ac unit that had an overly loud thud sound on startup. I attributed it to the compressor and ignored it for a few months. When the summer of 2016 rolled around the ac would not cool. I took it in to our local dealership and they replaced it with an identical unit (Dometic 651816C751C0) under warranty. The flow of air through the vents in the trailer seemed weak.This is something I had brought up with the service tech at the dealership and was told that the airflow was normal.
Last summer (2020) I noticed the ac wasn't cooling very much. We weren't venturing out much so we so I chose to ignore it. Fast forward to late June 2021 and we had a heat wave in the Pacific North West (100 - 110F over 3 or 4 days) and I wished I hadn't ignored the problem with the ac.
I tried remote troubleshooting it with the help of Darren at Myrvworks.com. The compressor's current draw was nowhere near what it ought to be - Normal should be around 11-14amps after running for 20 minutes but this was pulling ~7.2 amps. Darren told me I needed a new ac as the coolant had likely leaked.
I tried getting in touch with our local dealership and they seemed swamped. I did not get a response to a voicemail left with the service department. After waiting two days, I decided to order an ac directly from PantherRv.com and see if I could replace it myself. And I am so glad I did because I found all kinds of things that should have been addressed at the factory or at the time of the replacement of the first ac.
Our trailer has ac ducts(2015 was the first model year). The return air area between the inside and outside skin (it's a cavity of 3-4 inches where the duct-work runs) had no solid blocking of any kind, thus pulling in air from the cabin as well as the inner area between the outer and inner skin. There is a solid cross-member each to the front and back in this area but the sides were not sealed well at all. I had some aluminum foil tape and rigid foam lying around from another project so I made good use of them.
After uninstalling the old ac I looked underneath and saw that other than the rectangular foam gasket there was no foam separating the conditioned air from the return air. You can see what I mean in a Youtube video titled 'Airstream Travel trailers: Quietstream.' Pause at the 38-40sec mark and you can clearly see a piece of foam gasket that separates the incoming air from the outgoing air. This is in addition to the rectangular gasket that is stuck on the new unit. I reused a length of gasket material from the old ac and applied it to the new one.
Here's what the middle foam gasket looks like now from inside the return air cavity, just past the drain tube. No more mixing of conditioned and return air.
Another air leakage point was the opening on top of the trailer where the conditioned air enters the trailer. There is a black plastic transition box/plenum that the two branches of duct connect to. There are gaps between the skin of the trailer and plenum itself.
I was able to seal this with aluminum tape and thus make the air flow that much more efficient. The aluminum tape would not bond with the slick plastic, so I used some sandpaper to scour the surface. Make sure to clean the plastic shavings with a moist rag if you do this.
Having done just this much of sealing has considerably
improved the airflow from the vents.
The new ac had a Molex connector on the 120v power cable. I could have cut the connector and used a junction box but decided to order a Molex connector from mouser.com. It will make the connection process that much easier for the next person replacing/servicing the ac.
I also installed Microair's Easy Start 364 on the new unit. Roger at Microair was helpful with some questions I had regarding placement of the unit. A soft copper tube had to be bent
. They do not send out any connectors with the Easy Start, so if you think you will need them make sure to order a kit as well. I have a 30amp service outside our home but this was an add-on in case we need to use the ac with a Honda 2200 on our travels.
The ac is bolted down from the roof and I used some leftover Tempro 635 to seal the spaces under the foam blocks where the 4 bolts go in. The hardest part of the install was lifting the new ac on to the trailer roof.
I hope this helps the next person who is considering an ac replacement or has issues with airflow.