Dometic CU406C not cooling well - Fiberglass RV


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Old 07-10-2018, 07:28 PM   #1
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Name: David
Trailer: 2013 Scamp 16'
Wisconsin
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Dometic CU406C not cooling well

Ready to head out tomorrow. Turned frig on ac yesterday. Didnít come on tried moving elec switch gently each direction. Finally felt some warming in the heat tube. But several hours later, freezer compartment was cool, cold? Changed to gas, which fired up nicely and seemed to be working. Loading frig tonight. Doesnít seem to be cold enough. Guess Iíd better get scientific and stick a thermometer in it to know the facts.

What if it isnít cooling adequately. Where can I get the cooling gas(ammonia?).

Just wondering after hours. Could take action on the road tomorrow.

Would appreciate your suggestions. Iíll report the temp in the morning.

Thanks

David
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Old 07-10-2018, 08:14 PM   #2
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Update. After an hour thermometer measured 50F in freezer. Ugh!
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Old 07-10-2018, 08:20 PM   #3
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Name: Greg
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Quote:
Originally Posted by Dsironi View Post
Ready to head out tomorrow. Turned frig on ac yesterday. Didnít come on tried moving elec switch gently each direction. Finally felt some warming in the heat tube. But several hours later, freezer compartment was cool, cold? Changed to gas, which fired up nicely and seemed to be working. Loading frig tonight. Doesnít seem to be cold enough. Guess Iíd better get scientific and stick a thermometer in it to know the facts.

What if it isnít cooling adequately. Where can I get the cooling gas(ammonia?).

Just wondering after hours. Could take action on the road tomorrow.

Would appreciate your suggestions. Iíll report the temp in the morning.

Thanks

David
Well David,

There could be many factor for the fridge not cooling properly. Not sure what year your fridge is. Many important factors to consider and just eleminate them off the list. How level is the fridge. Not the trailer, but the fridge itself. Use a small 9 inch torpedo level to level the fridge in both directions. The fridge doesn't have to be more than a few degrees off level and this will affect the function of the fridge .
You probably already know this but electrical does not heat up as much as gas, so the cooling down will take longer and the recovery will take longer. For the little bit of cost of proane, I just cool down using gas.

When was the last time the flue was checked and cleaned ? Spiders and flies and many other creatures too many to mention love the smell of propane and love to build their nests in the chimney.

What is the colour of the flame, a nice blue is good and a dancing yellow is not. Then you would need to do a manometer check for the correct pressure of 11 inch water column. But just check your stove top burner and compare the colour to the fridge burner.

There is a spital metal piece in the chimney flue. Is it present and free to move, this causes the gases to swirl.
What temperature is the freezer compartment and the fridge itself.

How hot is the temp ouside and the humidity levels. If both are high the fridge has to work extra hard in cooling off, and the heat that needs to be absorbed by the outside envirnment maynot work at its best if the humidity and temp are both excessively high.
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Old 07-10-2018, 08:21 PM   #4
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You can't recharge the system with ammonia as it's sealed. Best bet it to clean the burner orifice and chimney to improve the flow & flame. Probably more to do with the chimney as AC was also underperforming; the boiler has both elements and the chimney is the common variable.
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Old 07-11-2018, 02:03 AM   #5
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Be sure you park in an orientation where the fridge is not on the west or south side of the trailer. Face the vent to the north if at all possible. You want the side with the fridge to be in the shade during the summer months.
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Old 07-11-2018, 05:18 AM   #6
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Temp in morning was 48F.

I vacuumed and blew area around burner. The insulating jacket around flu pipe doesnít appear to come off without bending tabs. Flame looks good. Here are pictures.
Oh, this 2013 Scamp. Click image for larger version

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Maybe I shouldnít expect 32F in freezer?
Itís been very hot, low 90ís in Wis., but 70ís overnight.

Weíll leave for RMNP. I may try an RV repair place on the way for a check. (?).

What do you advise?
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Old 07-11-2018, 08:57 AM   #7
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on the gas side you will need to pull the orifice and make sure its clean. on the other side of the orifice it goes into the burner tube. My trailer is parked outside. the burner tube and the back side of the orifice seem to attract spider nests. you need to remove the burner tube and check where the gas come in and inside the tube. A long Q-tip works well for wiping out any obstructions. Other than that its off to see someone to make sure you propane regulator is putting out proper pressure and flow.

The AC side is a simple resistance heater cartridge it either has good power with clean and tight connections. Inside the cartridge is a coil of wire for a heating element usually they just plain work or not. Sometimes they can work when cold and go open circuit when they heat up.

The biggest thing to check is the door gasket seal if the door gasket is letting the cool air out you don't have a chance in these little fridges. Take a strip of paper and close the door and latch it. if the paper pulls out with no tension on it you have a problem. Work the paper around the door gasket and check the whole perimeter.

I usually fire up the fridge 3 days before a trip and fill it up with pre chilled drinks. Can't really test an empty fridge in these little campers.
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Old 07-11-2018, 10:21 AM   #8
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Some of us have a lot of trouble with these fridges. I won't say you shouldn't expect better cooling, but for my fridge, 90s during the day and 70s at night would mean I'm using a cooler and turning off the fridge. Mine works great in the 60s and 70s, and just fine in the 80s so long as it's still cooling off to the low 60s or better yet 50's at night (which around here it does, luckily). But any warmer during the day or less cool at night means no recovery and the fridge is useless.

In general, yes, you should expect a well below freezing freezer and a fridge compartment under 40. With the above as the exception.

How much experience do you have using RV fridges?

Look up gas orifice cleaning (google). Depending on your mechanical aptitude and experience, it may or may not look slightly intimidating at first, but it's really a very simple job. The "difficulty" is just being careful to clean things properly, ie don't scrape the glass opening with something hard, don't blow dirt into the gas line. Just follow the instructions and everything is fine.

That looks like a nice, new, clean fridge so unless a spider or wasps got in there, I'm expecting that it'll be pretty clean...but obviously it's worth checking the chimney. Not sure on your fridge...on mine I have to remove the fridge to clean the chimney, as it needs to be done from the top. That's not really an "on the road" job unless you're traveling long term. Just use a cooler in that case.

I hope it's something easy like a spider or wasp nest, but I'm afraid it might just be that your fridge can't keep up at those temps.

There are a dozen little tips and tricks, many mentioned already, to get the fridge running as optimally as possible, squeezing a degree or two here, half a degree or so there. But without knowing how your fridge performs with daytime temps in the 70s or 80s with cool nightime temps, it's hard to say if this is an actual "issue" happening here, or just a fridge which, like mine, simply won't cool adequately at the temps you're experiencing no matter what you do.

If you can confirm that the fridge works great at lower temps, then we start getting into gas pressure (though you should test that anyway), adding exhaust fans, in-fridge fans, baffles and, finally, if you get near where I'm getting, sledgehammers.
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Old 07-12-2018, 06:49 AM   #9
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We traveled through 97F temps today. Freezer compartment was 30F. Thanks for being there to help a concerned Scamper.

I will check orifice and gas flow tube.

RMNP here we come, where temps should be lower!, maybe even some showers.
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Old 07-12-2018, 07:44 AM   #10
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[QUOTE=Dsironi;706919]We traveled through 97F temps today. Freezer compartment was 30F. Thanks for being there to help a concerned Scamper.

I recall reading a Dometic specification that stated a 50 degree reduction in temperature from outside temp was considered acceptable. It appears from the above numbers you posted that your unit is working satisfactory. When I'm in hot weather, I make sure to only put items in the refrigerator or freezer that are already frozen or as cold as possible. 97 degrees in the sunshine is a real challenge for any of these units.
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