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[Rortega46]

In the last 4-6 weeks the AC and heating unit has developed a problem and shuts down after a few minutes running time. The error code on the SMXii controller is “LO PS.”   FYI, it shuts down and displays LO PS in both heating and cooling modes.

It’s my understanding the SMXii HI PS error code indicates a lack of cooling water through the system, and the LO PS error code indicates a lack of air flow through the system.  I’ve cleaned the air intake filters, and the coils look relatively clean.  I’ve not checked the freon level as I don’t know the pressure spec and procedural steps to do this. 

If anyone has any suggested troubleshooting steps to resolve this problem it will be greatly appreciated.
 
Thanks to all for your help and may you have a Merry Christmas and a happy New Year.

[Ken Juul]

What brand heat pump do you have.  That might get some more answers.

[Rortega46]

Ken, thanks for the suggestion.  The unit is a 16k BTU Cruisair model FX16-P.  The plate on the unit has a lot of info and says Lo Side 150 PSI and Hi Side 300 PSI.  I’m still thinking the LO PS error is due to the unit being low on freon and plan to check it.  I’m wondering if no one else has seen the LO PS error.

[Ken Juul]

may want to look at this thread before you call the tech.
http://www.clubsearay.com/index.php?threads/cruisair-smx-ps-lo.13833/

[Rortega46]

There is some great troubleshooting info in the link.  I’ve cleaned air filters and water lines but the LO PS error continues.  It seems the next logical step is to check and top off freon.  Although I’d rather do it myself, I’m not confident of my ability and the steps to do this so it’s time to call a tech. 

[Rortega46]

It turns out the LO PS error code on my SMXII was due to low freon.  The AC/Heat system has been charged and working well now.