Frigoboat AV35F Won't Cool

[thunderhoof]

Hi,

I've been commenting on other's posts for a while, now I need some advice.
My boat has a vintage 2003 AV35F with air cooling used with a standard cold box that fits 2 ice cube trays.
Several years ago I found that the unit would work well for months unless I turned the refrigerator power OFF for several weeks. If I did that the unit would not cool well until I recharged it. (I checked and replaced all the gaskets I could find.) This worked well. I used a vacuum pump with A/C manifold gauges to pump down the cooling circuit, then added about 4 oz of R134A and all was well for most of a year.
This time that did not work. Where I am now is that after evacuating the unit, I recharged it until the gauge showed no more pressure increase. After sealing off the charge line, I powered ON the unit. I hear the compressor run, quieter than usual. The low side line pressure drops within 1 minute to -8psi and I cannot hear the compressor at all. When I turn power OFF, the low side pressure rises to about 40 psi within 4 minutes and halts there. I can repeat this by turning the power ON then OFF.
OK - what's up?

I am thinking that there is a blockage to/from the cold box. Can I disconnect the two connectors on the cold box line (they are on a line that is coaxial for most of the run) that are accessible at the compressor unit? I could then use pressure or vacuum to clear the blockage - If I can find some connectors that mate with the connectors on the line.
Thanks for any thoughts.

[OzeLouie]

Originally Posted by thunderhoof

Hi,

I've been commenting on other's posts for a while, now I need some advice.
My boat has a vintage 2003 AV35F with air cooling used with a standard cold box that fits 2 ice cube trays.
Several years ago I found that the unit would work well for months unless I turned the refrigerator power OFF for several weeks. If I did that the unit would not cool well until I recharged it. (I checked and replaced all the gaskets I could find.) This worked well. I used a vacuum pump with A/C manifold gauges to pump down the cooling circuit, then added about 4 oz of R134A and all was well for most of a year.
This time that did not work. Where I am now is that after evacuating the unit, I recharged it until the gauge showed no more pressure increase. After sealing off the charge line, I powered ON the unit. I hear the compressor run, quieter than usual. The low side line pressure drops within 1 minute to -8psi and I cannot hear the compressor at all. When I turn power OFF, the low side pressure rises to about 40 psi within 4 minutes and halts there. I can repeat this by turning the power ON then OFF.
OK - what's up?

I am thinking that there is a blockage to/from the cold box. Can I disconnect the two connectors on the cold box line (they are on a line that is coaxial for most of the run) that are accessible at the compressor unit? I could then use pressure or vacuum to clear the blockage - If I can find some connectors that mate with the connectors on the line.
Thanks for any thoughts.

I believe you are on the right track. The system has a restriction in the capillary tube. Often such blockages are at the entry to the capillary but not necessarily with R134a systems, specially those with only a spun copper strainer and not a proper filter dryer. It is likely that the restriction could be at the exit point, that is where the capillary joins to the evaporator.

What happens is that gunk rubs off the strainers beads and deposits on the interior of the capillary causing the restriction. The strainer, not having a felt filter and therefore not a true 'filter dryer' allows this gunk to pass.

This may require replacing the capillary and if you do I strongly suggest the following:
1: Ascertain the present capillary interior dimension and length. Use this chart to find an equivalent in the next size up equivalent. https://www.secop.com/solutions/comp...tube-selection
2: Fit a proper filter dryer like a Sporlan 032, flared fitting. (Outlet downwards, fit prior to capillary)
3: Evacuate with a 2 stage pump overnight then slowly recharge with refrigerant, with system running until a suction pressure of 10- 15 PSIG is maintained without further gas addition. Run and adjust charge (purge) if suction line frosts up.

If this is a bit daunting you might try just fitting the proper filter dryer, evacuate and recharge, you might get lucky!

This pic shows how the gunk can coat / restrict the capillary interior when a proper filter dryer is not used!!



Good luck!

[Nicholson58]

Ours managed to get enough moisture in the system for an ice blockage to form at the expansion orifice. Required hard vacuum for several days to insure it was dry. There is no dryer in these units.

[thunderhoof]

OzeLouis - Thanks for the guidance. I am in contact with a Frigoboat US dealer to buy a replacement evaporator with piping. It will be a workout to replace it because I am thinking this is the first part they pick up when they install a B40.7 galley so it is really buried. I will try to get lucky by releasing the main disconnects hoping to clear the blockage.

[thunderhoof]

By the way. If I were to install a dryer, where would it go and how would I adapt it to the Frigoboat tubing?
Thanks again.

[OzeLouie]

Hi again TH. My apologies, I had thought the leak was located / repaired. Upon reading your OP again it is likely that the evaporator has a very slow leak. This is common where the aluminium tubing joins to copper.

Frigoboats advice to replace is excellent but note that the rest of the system is most likely contaminated and essential that a proper filter dryer (032 or 052) be used then a good vac out with a two stage pump and warming of compressor and condenser while evacuating. (The new filter dryer is best after the condenser and prior to the capillary entry. Position so refrigerant flow is downward and towards the capillary otherwise locating anywhere is better than none!)

Most aluminium evap makers now seal over the suspect area but suggest checking the new one and if needed seal over as described below.

Replacing the evap with capillary, filter dryer, evac and regas is the correct procedure and should see you get many trouble free years to come.



Cheers Louie