Air Conditioner Problem

[Ken Krawford]

I'm trying to help a friend remotely troubleshoot a Marine Air problem.  The unit is older (15 yrs ??) but worked fine until recently.  A minute or 2 after startup the unit throws a HPF (high pressure fail ??) code and the compressor stops.
So far they've replaced the fresh water pump and run Barnacle Buster thru the unit but no success.  There appears to be an adequate amount of water discharging from the unit.  Phone calls to Marine Air (Dometic) tech support were unhelpful.
Any other suggestions on what is causing the compressor to kick out?
Thanks.

[Jon W]

Have you checked the Freon high pressure switch?

[Ken Krawford]

Thanks for the suggestion Jon.  Since I'm helping remotely, any idea where that switch is located?  I suspect it's on a PC board maybe.  Can it be tested with a multimeter?

[Jon W]

A couple CYA's for me -

1) You've checked the cooling water system and the strainer is clear, the hoses are clear, the impeller and motor are fine, and you're getting good flow of water in and out of the boat.

2) Installers and boat owners do "creative" things. Your friend should review the schematic for their system and match it to what is actually installed.

3) If you don't have a schematic, ask tech support where the high pressure switch is and what the replacement PN is.

Keep in mind without knowing what you actually have, I'm guessing here. I suggest you follow the 1/4" copper tube out of the compressor to the pressure fill port in the tube, after that you'll normally find a switch tee'd off the tubing. That should be the high pressure switch. If you jumper it out (at the switch or at the control board), then start the system, and it works without an error, you have a bad switch. Let me know what happens, I'm always learning.

[Ken Krawford]

Just to close the loop on this thread, it turned out that another Barnacle Buster treatment with the solution left in the system overnight did the trick.  Interestingly, the boat is (and always has been) in fresh water.  Thanks Jon for your feedback.

[waughoo]

Thanks for coming back to close the loop.  It is always a bit dissappointing when a thread just ends without the answer.

[Jon W]

I'm glad to hear you solved the problem. Thanks for letting us know.