I got to learn a lot about refrigeration since my last post.
Intermittent cooling can be caused by a blockage in the refrigerant circuit. I find that the best way to confirm that is to measure the power consumed by the compressor. Either with an amp meter or better with a wattmeter that will show voltage, amps, watts, max amps, max watts, total watts, total amphrs. They cost a handful of dollars on Amazon / AliExpress.
A blocked circuit will show the compressor consuming lower power (only 20W instead of 60/100W, but constantly). The evaporator will be cool (not cold) and sweaty. Stop/Start of the unit may cause the compressor to stall (stops itself, waits 30s and tries again), emitting the corresponding error code on the diagnosis LED (if you have one plugged in). The fan runs continuously during that sequence, which can be mistaken for the compressor running. Learn to recognise the various sounds.
The blockage can be due to ice crystals or corrosion sludge. Usually the blockage is on the capillary, the hair-thin copper tube leading to the evaporator plate, but can also happen at the entry of the evaporator, where the refrigerant expands and the temp gets super cold.
Ice crystals form because tiny amounts of humid air can be sucked in on the vacuum side of the compressor at the quick connector.
Aluminum sludge can form because of the corrosion of the evaporator plate by the refrigerant chemicals.
The filter drier, located after the condenser (the u shaped water circulation tube sitting on top of the compressor on our units) is meant to catch such impurities but can/will saturate at some point.
It’s difficult to differentiate between solid and ice blockage, but if the unit cools again after you let the evaporator warm up to room temp, you can hope it’s ice based.
You can also gently knock on the evaporator around the thinnest section of the embedded evaporator tube, with a rubber tool or snapping your fingers and hope to dislodge the blockage. You’ll hear a hissing sound and the evaporator will frost promptly.
Ice cristal issues may be resolved by changing the filter drier, vacuuming the system thoroughly and refilling with refrigerant.
Solid blockage types are trickier and usually need a change of evaporator/capillary, since they are located after the filter and before the capillary.
So there is a risk that changing just the filter drier may not solve the issue.
While you have someone onboard working at welding/brazing a new filter drier, ask them to remove the quick connectors and weld the circuit. Those quick connectors make it really easy to install the fridge initially but will fail and lead to refrigerant loss, humidity infiltration, and workhours of fridge engineers, some (many?) of them using the occasion to sell complete new fridges.
They are also an environmental nonsense because the will lead to people topping up with refrigerant again and again instead of addressing the issue. R134a refrigerant is better that freon but still an extremely potent greenhouse gaz.
A fully closed circuit instead of quick connectors vastly reduces risks of refrigerant leaks.
Access to the galley fridge/freezer compressor has been explained by Arno.
Hope this helps navigating the interesting world of refrigeration/AC engineers, whose charging of 100$ per hour in Tahiti for drinking your coffee (before 10am, your beer afterward) while everybody waits hours for the system to settle/be vaccummed/refill slowly/settles/etc, strongly encourages you to google a thing or two about fridges and potentially invest in gauges (25$), a vacuum pump (more expensive), canisters of refrigerant (only available to license holders in eco friendly countries) and maybe even an 02/propane brazing kit.
Rapa, French Polynesia
On 22 Jan 2022, at 05:11, Rudolf Waldispuehl <Rudolf@...
Hi Amelia’s, (@ Arno & Mohammad)
The Galley fridge on my A54 is only intermittently cooling and sometimes it stops completely until I can restart it. A fridge-guy told me; - it is the filter blocked inside the unit and it is a common problem on boat fridges. He mentioned, he need to take out the compressor to change the filter (just a 2€ part). But to take out the compressor on my A54#55, it seems I need to dismantle a big parts of the galley because the “service opening” is too small for the compressor replacement.
Does anyone know where this filter is located by any chance?
@ Arno/Mohammad, I have found in older treats that you had similar problems and you both changed the compressor. How was it gone and how to change the compressor without too much hazzle? The opening is too small, even if I’m able to remove the big wood panel galley front.
How was it in your case?
Thanks and best regards
Ice crystals would occur if the filling of the system was not done properly. There is a filter in the system that binds any moisture that may be left at filling time. Normally they replace this filter when refilling. Once a system is working properly there is no interference with the atmosphere so moisture cannot enter. If the system is leaking you may see moisture enter the system after so much gas has escaped that at run-time the low pressure side gets below atmospheric pressure (depending on where the leak is). If you still have the original compressors (you can see this by looking at the way the speed control works). The newer units use a rotary switch if I'm correct. If you still run the originals chances are you have a gas leakage, most probably at the quick-fittings. These are the screw connectors that connect the evaporator to the compressor.
In my case the problem was a leaking heat-exchanger (the tube on top of the compressor) that rotted away due to the salt water in the circuit. In the end I replaced all the compressors.