I have 2 Fridgomatic 35 F (Danfoss 12 volt) constant cycling style
compressors with evaporator plates. One for my fridge and one for the
freezer. The systems are completely isolated. But, both are showing
the same brand new failure. They are running continuously and drawing
about 1/2 their usual current and periodically they stop cooling.
They have worked perfectly until now, so it may be something to do
with the change to the continental climate here in California. But,
my theory is that they are both a bit low on R-134a (their coolant of
choice) and thus not getting the boxes cool enough to ever let them
shut down and at some point tripping a thermal switch on the
compressor. Yes, no, maybe?

Since we're in a marina in CA I'd normally just call a reefer-man.
But it is Friday afternoon -- when else? So, I'm wondering how wise
it would be to see if I can find a set of gauges and add some
refrigerant. Am I likely to cause more harm than good? Are there
tricks to this that a complete novice is apt to miss? ...

-- Tom.

Tom, are your units air cooled, water cooled or do they have keel
coolers? If there is a refrigerant problem it will show up by the loss
of frost on a portion of evaporator. Is there at least a thin layer of
frost covering 100% of evaporator? If not describe where frost is not
present. If water cooled do they both use the same water source? Are
these units equipped with Frigoboat’s SSC panel, if so is red LED
flashing? If so what is the flash pattern? If there is a single flash
and four second in between flashes there is a low voltage problem at
units.

Connecting gauges is always a mistake unit it is confirmed the systems
are truly low on refrigerant. The only things common to the two units
would be the boat’s electrical or possibly condenser cooling medium
air or water. If it is true they are both drawing ½ normal power this
would indicate refrigerant problem what happens if one unit is shut
off? Are the compressors hot to the touch.

Richard,

They're both air cooled. The freezer's evaporator currently has frost
all over it and the refrigerator's plate has cool condensation. I
cycled them both off and then on again and they seem to be working
now. The Fridge is down to temp and so the compressor is stopped and
cool. The freezer is trying to bring its box back down and its
compressor is running and hot and drawing about the right amperage.
The electronic controllers don't have LEDs but I just bought a couple
and will put them between + and D to see if the controller are
reporting errors. I also picked up a couple of tins of 134a and some
adapters and a hose with a low side gauge, but I'll hold off on all
that until I've looked at the LED output.

Thanks,

-- Tom.

Tom, if frost is present on at least 90% of evaporator at any time now
then refrigerant volume is correct and to tamper with refrigerant now
can be an expensive mistake. Non destructive troubleshooting should
always be first. If a unit does run continuous and the evaporator
surface area covered with frost is consistently less than 70% then
there has been a loss of some refrigerant.

Because both systems seem to now be working then I would look at the
only common item between the two which is the boats wiring. Most boats
with dual systems like yours are not wired in dependently of each
other to the main battery buss, this means any trenchant voltage spike
from another circuit can signal a compressor module to cycle off that
compressor.

Thanks for that, Richard. I got an LED on the freezer's compressor --
I'll do the same for the fridge in the morning but it requires
disassembling some furniture. My feeling now is that over-heating is
the most likely candidate. The compressors have often been in hot
weather but it is much less humid here in California than our usual
digs. But, I'm not totally convinced. It will be interesting to see
if the controllers show an error state at some point.

-- Tom.

On Sat, 21 Jun 2008 20:32:30 -0700 (PDT), "
wrote:

The compressors have often been in hot
weather but it is much less humid here in California than our usual
digs.

What would humidity have to do with anything? The things are hardly
sweat cooled.

Casady