frig cooling problem...with a Norcold 821

[ronbourd]

Please can someone explain me what "mechanically or chemically" goes wrong inside a Norcold 821 for the cooling becoming less efficient ones in a while, despite having good heat, good ventilation and being parked on level ground. What is really happening inside those tubings after 15 years of good service? thank you very much for the explanation!... Every body would like to understand that popular problem! Ronald.

[ronbourd]

Dougrainer, thank you for your comments. This class C rv was bought brand new in 099! May be we parked it off level a bit in truck stops, when we stopped for lunch , but level enough to cook on the store! I will take it off and bring it in the basement and rotate it a lots of times for a couple of weeks! If it is not correct, would you advice me to buy a "cooling unit"and change it yourself or would you just replace the complete frig for the" 841" IN québec I can buy a 841, witch replaces the "821" for about $2200.00cdn. For the last 9 years we camped on the "Bonaventure river" in the "wild" the average rate of propane is around 1 liter a day to keep the frig cold and this did not change much from years to years Before anything, I will do what you suggest me to run on bypass ac ,but I don't.suspect a heating problem. Up to 3 years ago we used to run it cooler with a lot of food in it .The fins would freeze very fast , so we had to unfreeze it(turning it off) every 2 weeks, then we realised that by making it run a bit less cool, there was no ice buildup on the "cooling fins) so no need to "unfreeze it" , and the foods were still perfect. From your experience, what is the normal life time of a frig that runs around 90 days a year. From Rimouski ,-27C outside ! Ronald.

[dougrainer]

From your description, you have a partially block cooling unit. Taking it out and burping it does NOTHING except let it work for a few days which is the exact same thing that happens when you do your turn off and then back on. If I had you unit, I would verify all operational criteria and then run bypassed on 120, for 24 hours. THAT will tell you the condition of a cooling unit. Your model, I would expect it to freeze water and get down to probably 26 degrees. I do NOT measure air temp, I measure the water temp inside of a glass of water. Have you owned the refer since new and have you ever traveled with it or just go to the same place or leave it at the same place year round? I KNOW you state never off level, but I find it hard to believe that in 15 years, you have never traveled and stopped for a lunch or overnight at times and the refer was out of spec level for those short times. Doug

[ronbourd]

dougraier, my camper was always parked level when the frig was ON ! What I dont understand is that when It became less efficent (propane heat always running and with a good flame) we turned the frig off for a couple of hours, then i turned it on and off for a couple of times, it returned to cool with a good efficiency, for 3 days.! Then it started to become less cold ,and we then took the habit to turn it off for a couple of hours and started again, and this seems to be the only way to get it back to cool normally!. The last summer when this appened, we were parked for 75 days. When we left to get home with the camper a distance of 200miles, ,the frig seems to cool normally. Before replacing it , how about taking it out of the camper and turning it upside down for a couple of weeks? What would you suggest me to do with this unit that still looks like new? how and what is the best way to "rotate" a frig? .The only time this frig is not level is when the camper is parked for the off season in my backyard! Thank you every one for your advices...

[dougrainer]

If NOT leaking, then in that 15 years, all those times (short and long) that you parked un-level with the refer ON, it caused a microscopic blockage on the upper tube area. This is a accumulative process, over the years those small blockage's build up and then one day you do not get the cooling you expect. This type blockage is permanent, you cannot Burp or rotate the refer to fix the problem. The blockage is as hard as a weld and cannot be removed. Years ago when they used to rebuild old units, they cut out the blocked tubing and welded new tubing in place since the blockage could not be removed. Doug

[Old-Biscuit]

Ammonia is heated to a vapor and then is condensed back into a liquid........the more that can be changed to vapor state the more can be condensed back into a liquid.
The more condensed back into a liquid the more heat can be adsorbed from the refrigerator sections (freezer/food). The more heat absorbed the colder the compartments.

Anything that inhibits/restricts any one of the processes (vapor/liquid/absorption) will cause less cooling.

[Chris_Bryant]

The most common failure is the percolator tube will simply get blocked, resulting in loss of circulation. This can be gradual, and is caused by slightly off level operation.
The other failures are gradual loss of hydrogen- can happen through slightly porous welds, and build up of another gas which is given off by overheated sodium chromate, which forces the hydrogen higher and higher in the tubing. You can tell this is the problem if the freezer is still working fine (i.e., zero or below), but the fresh food compartment isn't cooling correctly. This is also caused by off level operation.
You can look at this webpage for a good explanation.

[Joe417]

Ron,

The following web site is selling frig repair training classes but they have a series of free videos that explain a lot of the little issue that pop up.

Lots of good facts about absorption refrigeration that, if you understand a bit about physic, can help you understand a bit more about refrigeration.

Ford RV Refrigeration
rvrefrigeration.com/

Ford's RV Training Center is a Kentucky State Licensed Proprietary School. We teach RV absorption refrigeration reconditioning.

[chipper]

Go here for more info than you need.
https://www.google.com/#q=how+arv+fridge+works+diagram