3 year old Dometic doesn't work

[lewster]

Originally Posted by KJRitchie

After browsing the recoilingunit site for my fridge, Dometic 3762, they only offer a new unit which is a redesign of the Dometic unit. It would be interesting if someone performed a face off to see if the Amish unit redesign and ammonia formula gives better warm weather performance. With only two manufacturers left in the marketplace there isn't much incentive to innovate. Atwood is offering a fridge with helium but isn't helium in very short supply?

Do the Dinosaur boards allow you to tweak the fridge performance better than the OEM boards?

Kelvin

Some Dinosaur boards have a temperature regulator located right on the board (mostly designed for the Dometic units with no temp control) that allow you to adjust the cooling level in the fridge.)

I still feel that your best bet is to install a bank of 12VDC computer fans located at the top vent (either wall or roof) to PULL the hot air across the condenser, being certain that the hot air is actually being drawn out of the plenum and not getting stuck circulating around the condenser area.

I have probably 50 installations like this and all have worked well......especially in hot weather.

[KJRitchie]

I guess you have to remove the top vent to gain access to the upper vent area. There is wall baffling built on the AS walls that extend up to the condenser area, very tight fit even for my hand between the absorber tubes and the baffle.

If you install computer fans up there can you hear them running from inside the trailer?

This weekend we are going out and the weather is starting to get warm, lower 90s. This will the first trip I get to see how the fridge in our 2008 Classic 25 performs. I've had a couple of RVs since 1986 before we got this Airstream both with 3 to 4 cu/ft Domectic fridges. The fridge in our 1986 Natl RV Dolphin Micro motorhome had a new cooling unit after about 4 years despite keeping the motor home level. Had a popup for a year after the MH and can't remember that tiny fridge's performance and then these last couple of years a 4 cu/ft Dometic in a Casita. I figured the larger fridges could take warmer weather better because there is more cool air in the box to get warm, doesn't seem to to be the case for a lot of owners. I also think the humidity is a factor for these fridges, the higher the humidity the harder it is to maintain cool temperatures. I've come to the conclusion these RV fridges are not meant to be opened a lot so keep the beverages in an ice chest in hot weather.

Kelvin

[lewster]

Originally Posted by KJRitchie

I guess you have to remove the top vent to gain access to the upper vent area. There is wall baffling built on the AS walls that extend up to the condenser area, very tight fit even for my hand between the absorber tubes and the baffle.

If you install computer fans up there can you hear them running from inside the trailer?

This weekend we are going out and the weather is starting to get warm, lower 90s. This will the first trip I get to see how the fridge in our 2008 Classic 25 performs. I've had a couple of RVs since 1986 before we got this Airstream both with 3 to 4 cu/ft Domectic fridges. The fridge in our 1986 Natl RV Dolphin Micro motorhome had a new cooling unit after about 4 years despite keeping the motor home level. Had a popup for a year after the MH and can't remember that tiny fridge's performance and then these last couple of years a 4 cu/ft Dometic in a Casita. I figured the larger fridges could take warmer weather better because there is more cool air in the box to get warm, doesn't seem to to be the case for a lot of owners. I also think the humidity is a factor for these fridges, the higher the humidity the harder it is to maintain cool temperatures. I've come to the conclusion these RV fridges are not meant to be opened a lot so keep the beverages in an ice chest in hot weather.

Kelvin

I would remove the upper vent cover on your model and zip tie (yes, zip ties ) the fans directly to the screening below. There should be enough clearance to do this.

One fact that I learned when at Dometic for a week of certification training a bunch of years ago.......for every minute that the fridge door is open, the gas/absorption fridge takes up to one hour to recover the lost cold air.

How's that for inefficiency?

[NevadaGeo]

Hey Tim, could you de-engineer that unit to be manual temperature controlled, like set it to run almost full cold full time?

[Buttercup]

Perry - no need to. When we run down the road, that is exactly how it runs anyway - full on. It doesn't shut off as evidenced by the HOT boiler.

[Buttercup]

Gee - look what showed up on my doorstep today. Wonder what it could be...

[KJRitchie]

Is that the freezer coil sticking out wrapped up? I'd think that would get easily damaged in shipping.

Good luck with the install.

Kelvin

[Buttercup]

It is the freezer coil. I inspected it and it looks fine. They say if it gets bent in transition that it can be straightened.

[KJRitchie]

When are you planning to start the install?

Kelvin

[Buttercup]

This coming Saturday actually. That is my first day off. I'll be taking lots of pictures for y'all.

[Buttercup]

Well, I finally got the unit out of the trailer. I removed all of the hardware and used the pressure washer to clean off the back. I see a few things that I do not exactly like and I will point them out.

This is what I saw after a robust Pressure Washing.


The First thing I noted is that the slope of the moisture seperator just doesn't seem steep enough. Despite the deep crimp at the bend, the slope still seems shallow enough to allow condensed water vapour to enter the condenser. I have always expected this as an issue, but could never prove it.

I also noted some discoloration of theend of the bubbler/boiler. Actually, this discoloration extended over halfway along the boiler. The metal almost looks like it has a temper. Hard to believe for a system that quite obviously has liquid still in it.



The lower part of the boiler/bubbler seems unremarkable. Nothing unexpected here. You can see the chimney, and sleeves for the 12 volt and 120 volt heaters.

[Buttercup]

Interested in how your fridge works????

FRVTS No1 RV Refrigerators Misdiagnosed Dometic Norcold Advanced Theory of Operation - YouTube

[KJRitchie]

How does the replacement cooling unit moisture separator look? Are you talking about the pipe above the condenser. It seems similar to the 8 cu/ft in the youTube video but theres seems to have the crimp more towards the center.

The boiler looks pretty bad for only a 3 to 4 year unit but I have no reference.

Thanks for sharing

Kelvin

[perryg114]

Ok I gotta ask. Why don't they make these things out of stainless steel so you won't get perforations in the boiler area which seems to be the place they most often leak and corrode from the outside?

Perry

[lewster]

Originally Posted by perryg114

Ok I gotta ask. Why don't they make these things out of stainless steel so you won't get perforations in the boiler area which seems to be the place they most often leak and corrode from the outside?

Perry

Planned obsolescence. Or would you like to double the cost of an already outrageously priced appliance that offers substandard performance as acceptable?

As you can tell, I am NO FAN of RV gas/absorption refrigerators!

[Gene]

Lew, what's the alternative? Perhaps one that operates a standard compressor on 120 v. and switches to gas/absorption on the road and while boondocking. Gauging by how cheap window air conditioners are, I would think a compressor would be pretty cheap and get the box cold so the gas/absorption unit would only have to maintain it between shore power opportunities. They could also insulate the box better.

Gene

[KJRitchie]

Other than the automatic features of the RV fridge I haven't seen much performance gains since I owned my 1st RV in 1986. I had to manually switch over from AC to gas and if the burner blew out I had to manually light it. Performance wise I was hoping after entering the RV world again after a 18 year hiatus RV fridges performed better in hot and humid weather.

I noticed this last trip out the hole in the back of the fridge for the water to flow from the evaporator fin tray is so much bigger than the spout of the tray. I'm thinking of patching the hole with a piece of Reflectix silver tape then punching a little hole for the drain pan spout. I'll also seal the thermistor wire hole better.

Kelvin

[Buttercup]

Kelvin, I'll take better pictures today in better light of each segment of the unit before I pull it and post the pictures. The separator section(s) look quite well though. There is no evidence of leakage whatsoever. I didn't expect there to be leakage because the unit works fine at a standstill.

Perry, They are not made of SS probably because that is cost prohibitave but certainly a possability. I doubt that there would be much less of a leakage problem for these. As that tech said in the video I posted, he has never, ever, seem a unit rust from the inside out. Yes welds do crack and leak. but that could happen even with SS.

Lew & Gene, I don't think it is a matter of planned obsolescence because these units are easily reconditioned and placed back in service for practically every fridge made. As that tech said (and as an answer to the question of not using a compressor refrigeration system in these applications) road duty is fairly severe duty for a refrigerator. The absorbtion systems are very durable whereas MOST compressor systems have easy duty - they just sit there in your kitchen, whatever. Also the energy requirements for them are so high! Semi trucks have onboard generators just to run those units on the trucks. An absorption system requires only a few hundred watts to do the same job, but it does it slowly, and that bothers people who want things cold, now.

[perryg114]

The stainless steel would prevent oxidation from the outside due to heating the metal so hot and not to prevent corrosion from the inside. I think these things fail because the boiler rusts from the outside and starts to leak. There are other issues like factory defects and owners not leveling these things properly. I would like to know what I can do to prevent the unit I have from failing. I don't want to spend $1200 on a new one and have it die in a few years.

Perry

[Buttercup]

It would be interesting to know if these fail from a rust situation or a cracked welds more often.