2 way dometic rm360 fridge not cooling properly

Submitted: Sunday, Feb 24, 2013 at 14:43
ThreadID: 100732 Views:7443 Replies:2 FollowUps:1
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hi guys i have a dometic rm 360 fridge in my pop top van that we are having trouble getting the temp to an accepatable level so far on gas the best we can get is 12 deg on 240not much better. any ideas on where to start would be gr8 thanks andy
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Reply By: vicw4114 - Sunday, Feb 24, 2013 at 15:52

Sunday, Feb 24, 2013 at 15:52
This is the advice I have given others on this problem:
Re fridge not getting cold. If you have the fridge more than 3 degs out of level the fridge might not work. The ammonia in the mix has a dose of chromate in it and this can boil off. My method if the unit is getting hot and not working is to remove and tip upside down and wait till the gurgling sound stops. Whilst it is upside down for hour trace the flow of the solution in the pipes...then with a gas torch heat the pipes and give them a medium thump with a rubber mallet. Turn the fridge onto the side where the fluid will go to next and heat and thump as before leave until gurgling stops. Stand fridge upright and give another heat and thump paying attention to where the high pressure line comes out of the tank(boiler)...this is the thin pipe. Now leave for 1-2 hours and then try fridge on electricity (for up to 8 hrs.) before reinstalling into van. With this heat and pump method you are trying to expand the steel tubes of the unit and to clear any blockages. BUT before you do this check the flue to see that the baffle (a twisted piece of metal on a wire which hangs in flue) is still there and hung into place. If it is missing or has fallen into the bottom of the flue the fridge will perform like it has a blockage. Most absorption fridges which are working Gas and Electric have two thermostats. One which is Gas and the other which is AC. So can presume that it is unlikely that both will become inoperable at the same time.
Another thing to look at are the thermostat tube attachments to the evaporator .Are they still attached? Another...In Electrolux or Dometic fridges for example the evaporator attaches directly onto the unit with screws .Between the the evaporator and the unit is a layer of conductive paste. Are the screws still tight? Is there anything covering the fridge vents in the van either at the side of the van or underneath the fridge. The latter will also cause poor performance.
In most cases the baffle can be retrieved by inserting a pair of long nose pliers down the flue from the top end and just lifting it out. The wire usually just hooks over the lip of the flue.
On the right hand side from behind the fridge you will see the boiler tube covered in insulation material. On really old fridges this is was of a square shape and on later fridges cylindrical and indicated that the tube has the later designed boiler tube. This modification was made so that the fridge would be less susceptible to blockages due to out of level situations but although it helped it was not a totally success.
Diagnosing the Cooling Unit:
Three things must be remembered
1. Circulation within the cooling unit is totally gravitational. This means proper levelling is so important
2. Heat created to boil the ammonia has to dissipate into the surrounding air.
3. Proper heat at the boiler section.
4. After the unit has been operating for approx. 1 hr. carefully touch the unit at the boiler box and the absorber area. These areas should be approx. the same temperature regardless of the outside temperature. Equal heat between boiler and absorber indicates that fluid circulation is ok
5. If the unit is blocked or partially blocked ...to the touch this unit will be extremely hot at the boiler with little warmth at the absorber
6. If you have a leaker this unit will be warm at the boiler and extremely hot at the absorber. In this case you are still boiling ammonia but have no hydrogen for evaporation. Check for an ammonia smell around the cooling unit and inside the fridge. This could indicate a leak. Check for any deposits of yellow powder on the tubing which will sometimes form around the area of a leak. Yellow deposits around the fill valve can occur during manufacture and doesn't indicate a leak.
7. If the unit works on one heat source and not another ….this is not an indicator of a bad unit.
8. Make sure that the fridge is level. Sometimes the vehicle is level but the fridge is not due to poor installation. Place a level on the bottom of freezer compartment and check side to side and front to back level.
9. Check door gaskets. A leaking gasket can allow enough warm air inside the refrigerator to overcome most of the cooling being produced. Use a paper bank note. Close door on the note. If no resistance is felt when pulling it out..,the gasket is not sealing properly. Do this on all four sides.
10. Check the venting system to ensure ample air flow is provided at the back of fridge.
I had one case where a customer’s cardigan and a bath towel had fallen to the back of fridge.
11. During cold weather don’t heat up your vehicle like an oven inside. These fridges work best up to approx. 70 degrees fahrenheit (21 degs celsius)outside temperature(ambient). For every degree that the ambient goes up the temperature in the fridge will go up 1 degree.At 70 farenheit the test temperature is approx.49 farenheit (9.5 Celsius).
12.Are you getting too much voltage drop at the element?
The points that I have given to are as I thought of them and are not in a specific order.
Particularly note item 11.
I hope that these few points will lead to some success with your fridge
Regards
vic4114
AnswerID: 505452

Follow Up By: Andrew C21 - Sunday, Feb 24, 2013 at 16:55

Sunday, Feb 24, 2013 at 16:55
thanks heaps will see how we go and let u know.also do you know what the normal temp should be?im assuming the same as household fridge 4deg.
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FollowupID: 782396

Reply By: vicw4114 - Monday, Feb 25, 2013 at 08:46

Monday, Feb 25, 2013 at 08:46
Andrew
there has been a major change to Dometic(Electrolux) absorption Fridges in the last ten years.You can now get them in as normal(which I suspect you have);subtropical and Tropical.The subtropical and Tropical are identified with either an S or T in the Serial number.I believe that it is a change in the ammonia mixture.
The latter 2 will work a lot better at higher ambient temperatures.BUT levelling and the efficient extraction of heat are still major concerns.There have been other changes but mainly to do with gas ignition and source.As I said in my post the temperature in the fridge at optimum conditions should be around 9.5 degrees celsius and minus 1.7 approx in freezer with an ambient temp of 21 degs celsius.For every degree that the ambient rises the temp will go up in the fridge and the freezer.
Disregard the temps in compressor type fridges as a guide.The S and T fridges get to optimum temperatures in higher ambient.
The most efficient source for the fridge is Gas.
If you look back through the forum posts you will see an excellent post on how to put a few extraction fans in and also behind the fridge to get rid of the heat.
Regards
vicw4114
AnswerID: 505490

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