First of all, as promised, here is a better picture of the boiler outlet and the discoloration I saw in the metal there. This does not look like a leak to me, just looks like metal that was under some high temperatures.
The baffle as I pulled it out of the gas heat tube. This is something that should be looked at if you ever pull your fridge for any reason. Inspect this! Nothing remarkable here.
So, to pull the unit, after removing all the screws and all infrastructure I placed a pry bar on the coils as shown. A slight tug and it was separated but not free. Note: The piece of wood is there to protect the delicate undersurface.
The cooling unit was loosened but I could not wrestle it out by hand, so i had to apply a little coercive force on th efreezer coils. I stood the unit upright for this step and tapped on the low temp evaporator coil with a rubber mallet for this step. It moved easily and I did not have to be overly aggressive at this point.
I easily pulled the old cooling unit at this point and set it aside to remove the last item - the high-temp coil heat exchanger, AKA the fins in the fridge compartment.
A big surprise for me when I removed the fins off the high temp evaporator - there was NO THERMAL MASTIC
at all between the fins and coils. To me there is ineffective heat transfer capability in this situation. The thin layer of adhesive aluminium is not what I would think of as an effective heat transfer layer. I can see this as being part of my problem. Dometic
, if you are reading this
, I think you can do better than this in my opinion. There is minimal thermal bonding here.
Prior to inserting the new cooling unit I inserted a thermocouple at the functional input to the high temperature evaporator, or what could be thought of as the outlet from the low temperature evaporator. The TC is embedded against the tubing in the foam with some thermal mastic and aluminium tape to hold it all in place. OK, I know this is putting me in the category of a geek and perhaps by some acounts a Loser, but I don't care, I have to know what the temperature of whatever ammonium is reaching this point in case this unit does not work for me. See, if the freezer is COLD
, there will be plenty of liquid ammonia reaching the high temperature evaporator to cool the fridge body. The TC is under the strip of aluminum tape above the fins.
I also placed a thermocouple at the inlet to the condenser after the last moisture seperator to see what the temperatures were at that point. Each subsequent TC I placed is hose clamped in place with a piece of fibreglass cloth as a protective barrier between the clamp and the metal.
I also placed a TC at the boiler outlet.
And I have one placed at the lowest point of the condensed ammonia inlet to the fridge. This point the ammonia is (or should be) in liquid form and it is further cooled by the high temperature evaporator as it is paralleled along that circuit on its way to the low temperature evaporator, further cooling it.
I may place another TC at the outlet of the high-temp evaporator prior to going into the absorber coils. I think this will give me a good idea of how this unit is working on the road. I know all of this is a little overboard to place TC's all over this unit like I have, but I don't care. I am totally in learning mode here and I do hope that somehow my data gathering here will allow for us all to learn how these units work in normal or even abnormal situations.
I wish that Dometic had data for what a unit like this runs at so people could better diagnose their units, but they do not. The Dometic "rep
" I talked to told me to call my local repair facilities as they did not offer the type of support I was asking for. One minute with my local "certified" individuals told me that they had basic knowledge of these units, but had no in depth knowledge of the basics of the cycle. Faced with a problem like mine and they simply locked up and said "I can't help you".
Anyway, next step is to re-install the fridge and run a new test with all my data logging stuff in service. Watch out!!!!!