Post edited 8:15 am – March 20, 2011 by geoffschultz

My boat has been sitting in San Diego since shipping it there in November. At that time the 13 year old Marine Air 16K split system was working fine. We just returned and found that the AC wasn't cooling or heating.

I put gauges on the compressor and saw that I wasn't getting any compression. I thought that perhaps that I had a leak, so I vacuumed the system, but found that it held the vacuum overnight. I then recharged and once again saw that I wasn't getting any compression when cooling. I then ran some tests and am quite confused by what I'm seeing.

In cooling mode, I see the low pressure side reading decrease as expected, but I see no pressure increase on the high side. When I put it into reverse cycle heating mode, I see ~115 PSI on what would normally be the suction side, but there is no pressure decrease on what would normally be the discharge side as measured at the rotolock valves on the compressor.

The compressor is clearly generating compression as shown by the heating cycle. I'm absolutely stumped as to why I see no changes in pressure at the discharge rotolock valve.

I ran some more experiments since writing the above.  I've closed the rotolock valves so the compressor is isolated and I'm only accessing the lines to/from the air handlers.  I vacuum the system and then open either side, and I see no pressure change on the opposing side.  Am I correct in assuming that air/gas should flow through the evaporator given 30Hg of vacuum and 1 atmosphere of gas? 

If that assumption is correct, then it appears the something completely blocking the lines.  At this point I'm guessing that the capillary valves are blocked.  Is this a reasonable guess?  If so, how would this have happened and can this be fixed?   Other guesses?

– Geoff

Thanks for the feedback, but there are 3 "ports" on the service valves.  The top port connects to the guages, the middle goes to the lines to the air handler and the bottom got to the compressor.  Normally the valves are in the up position.  When I move it to the bottom, aren't I isolating the compressor?  

I understand how the reversing valve works…or is supposed to work.

– Geoff

Post edited 10:11 am – March 20, 2011 by geoffschultz

Steve,

Thanks for pointing out something that I didn't realize…that the guage ports on the Marine Air system have Schroeder valves.  My refrigeration system doesn't have Schroeder valves. Anyhow, due to access restrictions, I had reversed the HP hose so that the end with the pin which depresses the Schroeder valve was at the gauge end!  Duh…Won't make that mistake again.

Now it's back to taking some real readings and diagnosing this.

Thanks again! 

– Geoff

P.S.  Both service valves are configured the same.  The bottom port goes to the compressor, the middle to the lines to/from the air handler and the top to the gauges.