Author Topic: Gas RV refrigerator failures!  (Read 5771 times)

Offline 78brave1

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Gas RV refrigerator failures!
« on: July 22, 2012, 11:07 AM »
Why They Fail
Gas RV refrigerator failures
How They Fail.
There are only two main failures with gas RV refrigerators (Dometic, Norcold and selected other).
 
 #1 The RV refrigerator is run unleveled causing the cooling unit boiler to overhead, block and crack.
 
#2 The RV refrigerator cooling unit's steel tubing rusts and the ammonia/hydrogen gas leaks out.
 
Note: A few less reputable operators in this industry feel that when the cooling units of these RV refrigerators fail that they can be just recharged without further repair. This is not repairing and the unit will lose its charge quickly.
 
Gas RV refrigerators do not operate the same way as other refrigerator types. They are charged with four types of chemicals and this mixture must be exact for the unit to work properly. The four chemicals of the charge are.
 
 
bullet height=15Water
bullet height=15Ammonia Gas
bullet height=15Hydrogen Gas
bullet height=15Rust Inhibitor powder
 
Boiler blocks or cracks - If the refrigerator is run while not leveled for an extended period, the cooling unit water will not flow into the boiler. The boiler as a result gets excessively hot and can bake the rust inhibitor. This will in-turn block the small 1/4" tube in the boiler and all flow will stop. If the refrigerator is kept running under these circumstances the boiler tube will get so hot that it will crack open.  If this happens a yellow powder around the burner area may be visible indicating that the cooling units rust inhibitor is leaking.
 
Leaks - When a unit rusts and leaks as a result, the ammonia gas is lost first. You can sometimes smell the ammonia gas. However when the door is opened or if the leak is small there can be little or no smell. Under these circumstances there could be a boiling sound at the back of the refrigerator. This means the hydrogen gas has also leaked out and the water is now boiling. Ammonia smells or large gurgling sounds from the refrigerator are indicators that the refrigerator cooling unit is leaking. 
The single biggest killer of gas refrigerator cooling units is corrosion. The common misconception is that it's the rust on the exposed pipe at the bottom of the cooling unit (down by the burner) that causes the leaks. In fact, this is rarely the case. The rust often seen on the exposed pipes is largely superficial even though it may look terrible. In gas refrigerator cooling units, the worst corrosion always occurs on the evaporator piping (the pipes that get cold) because they are physically located inside the refrigerator cabinet (right behind the back wall of the interior) and is covered by insulation. While the refrigerator is running, moist air finds its way to the cold evaporator pipes and condenses on the surface. Since the evaporator pipes are encased, the condensed water cannot readily drain away and therefore is held next to the steel pipe. After several years rust develops.
 
The rusting is accelerated when the refrigerator is turned off for the season, allowing the evaporator to warm up. The rusting eventually progresses to a point where severe pitting occurs in the surface of the steel. These pits eventually extend all the way through the pipe wall into the inner space of the pipes. The result is a leak.
 
You will usually, but not always, smell the leak when it occurs. If the leak does occur on the outside piping, you probably won't smell it. Sometimes, even if the leak is on the inside, you may not smell it if mostly hydrogen is leaking out. Most of the time, however, you will know that your refrigerator is leaking because of the pungent ammonia smell coming from inside your cabinet.
 
 After your refrigerator starts leaking, it will eventually (usually very soon) stop cooling. The worst thing you could do at this point is to delay getting your refrigerator repaired because corrosive ammonia is eating away at the cooling unit steel (ammonia doesn't corrode the steel while it's inside the cooling unit because of the rust inhibitor inside). The longer you delay getting your refrigerator's cooling unit rebuilt, the lower the odds are of a successful and reliable repair. Also the ammonia gas will eat up the inside of the cabinet and the parts. The light and thermostat will need to be replaced if left too long and the inside plastic will turn yellow. You can see why removing all rust from the cooling unit by sand blasting and rust proofing the cooling unit are essential steps in a proper cooling unit repair. Just as with your car, if you don't remove the rust, it'll just come back and, after another season or two of use, the cooling unit will fail again.
Running While Not Level
The second biggest killer is running unleveled. When the refrigerator is operating, water moves around the pipes and flows down the coils on the back into the main storage tank. The pipes on the back all slope down from side to side. When the RV is off-level, one direction of the coil will be flowing up-hill and the water flow will stop. When this happens there is no flow to the boiler section and the water in the boiler pipe boils dry. The rust inhibitor dries up and blocks the boiler tube. If the unit is kept running the boiler pipe will get so hot that it will crack from the gas pressure inside the coils (450#). Now the cooling unit is really dead.
 
 Never believe the stories that the newer units do not need to be run level? They are made to run more off-level than the older units BUT there is still a point where they will stop working. Always try to level you RV, as best you can, and if you have to park for a long time and cannot level the unit, shut down the refrigerator. It will keep the food cold for hours. Most of the newer units we repair have all been run unleveled and cracked the boiler. (This can be a very costly mistake)

Offline gadgetman

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Re: Gas RV refrigerator failures!
« Reply #1 on: July 22, 2012, 11:30 AM »
Nice Info there ! Another reason I love my modified 12v compressor fridge. I dont have to level anything  :)clap





Offline Woodybago

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Re: Gas RV refrigerator failures!
« Reply #2 on: July 02, 2016, 06:40 PM »
Great article. We have a dometic 4cubic feet in our Brave that doesn't work. The previous owner recommended that we burp the fridge by pulling it out and turning it upside down for a time before reinstalling it to revive it. Have you ever done this or heard about it?
Dan

Offline M & J

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Re: Gas RV refrigerator failures!
« Reply #3 on: July 02, 2016, 11:15 PM »
It's done all the time and works.
M & J

Offline Rickf1985

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Re: Gas RV refrigerator failures!
« Reply #4 on: July 03, 2016, 10:34 AM »
Nice Info there ! Another reason I love my modified 12v compressor fridge. I dont have to level anything  :)clap





How much power does that fridge draw?

Offline 87Itasca

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Re: Gas RV refrigerator failures!
« Reply #5 on: July 08, 2016, 11:04 AM »
I need to replace the cooling coils in mine, but now my concern is that the ammonia has eaten up the backside of the fridge, and I'll waste $500 on coils.

The inner shelves now have a light white corrosion on them, presumably from the gas. Steel wool would likely remove it, but I don't know.

 

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