Saturday, March 18, 2017

Is the fridge supposed to be warm?

Those words strike fear in the hearts of just about every cruiser.  Our air cooled Frigoboat AH35F refrigeration was installed by the previous owner and has worked flawlessly since we bought the boat.

The most likely culprit of a failed fridge is the evaporator plate.  It is made out of thin painted aluminum and a small bit of corrosion can cause a leak.  This is a $100 fix.

The next most likely cause is the compressor.  Either the actual compressor or the electronic controller could cause this malfunction.  These cost $300 and $200 respectively.  The good thing about these units is that one company, Danfoss, makes them and spares are available everywhere.
The compressor seemed to be running but not very hard.  The current draw, which is usually around 6 amps, measured only 2 amps.  When attempting to release some gas from the access valve to see if there was pressure in the system, nothing came out.    Could be the valve, or more likely, there's a leak somewhere.

We carry freon charging hoses and guages.  Usually you can buy 12 oz cans of R134a freon at the auto parts stores.  It's the same as used in automobile air conditioning.  Not here in Malaysia apparently.  All you can buy here are 30 lb. tanks.  I found a guy that had one with about 1/4 remaining so I bought it from him.

New High Temp HNBR O-ring Installed
I pressurized the system with a little freon and immediately found the leak.  Turns out that it was a failed o-ring at the quick disconnect fitting.

With that fixed, I did 5 fill/vent cycles to get most of the air out of the system and then did a full system charge.
Purging and Charging the System

Two good references to use for servicing these little systems are:


Evacuation Procedure without a vacuum pump
1.  With the new compressor installed, turn on the compressor and depress the access valve on the high side of the system.  Monitor the pressure on the low side of the system.  When the pressure is as low as it will go, close the access valve on the high side of the system and turn off the compressor.  This process will take about 5 minutes.
2.  Charge the low side of the system to approximately 14 psi.
3.  Wait about 3 minutes for the pressures on the high and low side to equalize.
4.  Turn the compressor on and depress the access valve on the high side.  When the pressure on the low side is as low as it will go, let the high side access valve close and turn off the compressor.
5.   Repeat steps 2, 3 and 4.  Note, on successive evacuations, the low side pressure will not go as low because of the absorption of refrigerant in the compressor oil and it’s slow release.
6.   Charge the low side of the system to approximately 14 psi.
7.   Wait 3 minutes for the pressure to equalize.  Turn on the compressor and depress the access valve on the high side.  This time, when gas is no longer coming out the high side access valve, let the valve close.  The air is now purged from the system.
8.   Charge the system with the appropriate amount of refrigerant and turn on the compressor.
9.  Make appropriate adjustments in system charge if necessary.

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