Why does the fridge take so long to get cold ?

[abbear]

I wonder if your camper has had the referigerator operating while not level.

From the dometic manual

IMPORTANCE OF LEVELING A REFRIGERATOR

In an absorption refrigerator system, ammonia is liquefied in the finned condensor coil at the top of the refridgerator,  The liquid ammonia then flows into the evaporator (inside the freezer section) and is exposed to a circulating flow of hydrogen gas, which causes the ammonia to evaporate, creating a cold condition in the freezer.

The tubing in the evaporator section is specifically sloped to provide a continuous movement of liquid ammonia downward by gravity through this section.  If the refrigerator is operated when it is not level and the vehicle is not moving, liquid ammonia will accumulate in the sections of the evaporator tubing.  This will slow the circulation of hydrogen and ammonia gas, or in severe cases completely block it, resulting in a loss of cooling.

Remember to level the vehicle when stopped for more than an hour, otherwise the cooling unit could be permanently damaged due to overheating if it is left "ON".

When the vehicle is moving, the leveling is not as critical as the rolling and pitching motion of the vehicle will pass to either side of level, keeping the liquid ammonia from accumulating in the evaporator tubing.


First thing I wondered was is your pup level?

[mike4947]

Being out of level doesn't really affect cooling. What it does is to allow pockets of the working fluid to stagnate and form crsytals. These eventually block the passage. Folks that have had it happen do not usually see a reduction of cooling. It's more of a "it just stopped cooling".
 
The crystals can not be redisolved and if the tubing gets blocked there is no permanent fix except replacement.
 
BTW fridges manufacturered since about the mid 90's will operate quite a bit off level without damage. The manfuacturers redesigned the tubing layout to allow greater out of plumb without the fluid stagnating.
A 3 degree out of level which would be 4.4 inches on a 7 foot width and/or 7.5 inches over a 12 foot box length is considered within spec.

[AustinBoston]

BTW fridges manufacturered since about the mid 90's will operate quite a bit off level without damage. The manfuacturers redesigned the tubing layout to allow greater out of plumb without the fluid stagnating.
A 3 degree out of level which would be 4.4 inches on a 7 foot width and/or 7.5 inches over a 12 foot box length is considered within spec.

That's the way I've always thought about it; level for comfort and the fridge will be fine.

But some people park their pop-ups off level.  If they then try to pre-cool the fridge, then they will need a new fridge (or switch to coolers).

Otherwise, the fridge has virtually no moving parts, and should last longer than the trailer.

Austin

[abbear]

From RVMOBILE:

Cooling Unit Diagnosis

The cooling unit, or coils, of an ammonia absorption refrigerator is the heart of the refrigerator--it does the actual cooling. Everything else on the refrigerator either supports the cooling unit, or is an accessory. No matter how simple or complicated the controls of the refrigerator are, all cooling units require the same three things to operate:

The unit has to be level
The unit has to have adequate ventilation
The unit has to have CORRECT heat
A fourth issue is raised if the cooling unit has recently been changed. The cooling unit has to have been properly installed into the refrigerator.
If the three above requirements are provided to the cooling unit, it should work and should work well. If it doesn't work well, then it is a bad cooling unit. It's really that simple. (Also, failure to meet the three requirements above when the refrigerator is in operation can cause permanent damage to the cooling unit.) Of course, don't overlook mitigating circumstances such as a main door that seals very poorly, which would cause a good cooling unit to look bad because of warm air continuously entering the box.

Also, if the cooling unit seems to work poorly only during warm weather, it's possible that one of the requirements above is in a border line state. In other words, the venting, for example, may be adequate for mild weather, but not adequate for warm weather. A cooling unit could also be border line, but it would be prudent to look elsewhere first.

Testing the cooling unit

First of all, if the cooling unit cools properly on one heat source (i.e. gas or electric) and not the other, then the cooling unit, with only a few exceptions, is good and the problem lies in the heat source that is not functioning properly.

Secondly, there are obvious signs of a bad cooling unit.

If you smell ammonia in or around the refrigerator, and you haven't recently used ammonia for cleaning, the cooling unit is bad. No further testing is necessary.
If sodium chromate is present on the outside of the cooling unit, the cooling unit is bad. Sodium chromate is a yellowish-greenish powder in solution inside the cooling unit. If sodium chromate is outside the cooling unit, the cooling unit has a hole in it.
If you hear a relatively loud gurgling or percolating sound when the refrigerator is in operation (being heated), it is a sign of a bad cooling unit. The key words here are "relatively loud". A good cooling unit percolates when in operation, and if you get close enough and listen carefully enough, you can hear it percolate. However, if you hear noise a few feet away, it is a sign that the cooling unit has lost pressure and is bad.
Testing the cooling unit is simply insuring that the three necessary requirements for the operation of a cooling unit (level, ventilation, correct heat) are met. Do whatever it takes to meet these requirements. If you suspect a venting problem, pull the refrigerator and set it on the floor. In fact, pulling the refrigerator and setting it on a level floor meets two of the requirements and leaves only one, correct heat, to worry about. Always test the refrigerator on the electric heat source, unless you are unable to because you have a gas only refrigerator. The reason for testing on the electric side is if the electric heat element gets hot, you can be better than 95% sure that you have correct heat, whereas even a poor gas flame will produce heat. To insure that the heat element is getting hot, you can touch the insulation pack (a rectangular or round sheet metal container filled with insulation located directly above the propane burner) to see if it is warm after about a half hour of operation. CAUTION: touch the pack lightly at first; it is possible under certain conditions for the pack to get super hot and burn you. If the insulation pack does not get warm, you have an electrical problem that needs to be corrected before continuing. If an electrical problem is not the electric heat element itself and/or you want to insure that some other electrical component (such as a thermostat) is not interrupting the heat element, you can hot wire the heat element for better testing conditions. The only weak link in this testing procedure is the less than 5% of the time that a working heat element is not producing the correct heat. See hot wiring for information on verifying the output of the heat element.

After you have provided the cooling unit with its three requirements, allow plenty of time for the cooling unit to function. You should see signs of cooling in the freezer after about two hours. Allow six to eight hours, or even over night, for an empty refrigerator to come down to temperature. The ammonia absorption style of refrigeration is slower than the compressor style in terms of initially bringing the refrigerator down to temperature. However, once the desired temperature is reached, there should be no problem in maintaining that temperature.

If you have done everything in this section up to this point and the cooling unit does not work or does not work well, the cooling unit is bad and will need to be rebuilt or replaced.

How to Change a Cooling Unit
Home
//www.rvmobile.com

From the Norcold FAQ's page:

How level must my refrigerator be?

If you have a gas absorption refrigerator, normal leveling of the vehicle is sufficient. The refrigerator is made to operate within 3 degrees off level side-to-side and 6 degrees off level front-to-back (looking at the front of the refrigerator). Our AC/DC refrigerators (both Built-ins and Portable) will operate at angles of up to 30 degrees off level in both planes.



I don't want to beat a dead horse but these sites both say that to work properly your unit needs to be reasonably level.  And if I recall correctly, when crystals form from using it out of level they may not block the tube completely but impair the recirculation of the gasses which in turn can impede the performance of the unit.  The first article also gives a pretty complete plan to figure out what, if anything, is wrong with the unit.

Not lnowing how long you've owned the unit or how it has been used this should be a good place to start.  RVMOBILE has more tools on their site to help you with this.

Good luck.

[ScoobyDoo]

Has anybody tryed putting empty bowls with lids in the fridge to replace the food. The cool air in the bowl wouldn't run across your feet when you open the door. I never tryed but thought about it while hunting for breakfast.

[wavery]

Has anybody tryed putting empty bowls with lids in the fridge to replace the food. The cool air in the bowl wouldn't run across your feet when you open the door. I never tryed but thought about it while hunting for breakfast.

It would actually be more efficient to put balloons in the fridge to capture the cold air. This may sound silly :p  but I sometimes take plastic grocery bags, blow them up and stick them in the fridge (if it's hot out). It takes up the empty space (as we use up items that are stowed in there) and does not allow the cold air to spill out when the door is opened.

[gypsy_soul]

On my dometic 3way, I've found a couple of things to help cool it faster. ! is a little fridge fan from wal-mart ($16.00) that runs on 2 d batt. says it will run for 30 days, helps move the air. Then for the outside, I've mounted a little solar fan that moves the air over the fins, making it more effecient.

[trailwart]

i have a 1985 viking that had cooling problems,  found that the exhaust tube by the pilot was filled with cobwebs. blew all the webs out and blew all components in the compartment and has solid ice in my ice trays in 4 hours.  worth a look