No heat P5(PS) LO Error

[Dawn Norakas]

Went back to the boat to get ready for Spring. Turned on the heat (which ran fine in Dec) the front heat is fine but the aft heat is blowing cold and is giving me a P5(PS) LO Error code. I googled it and I know it means low pressure, but what do I do now?

 

[jpk33]

While the unit (with the error) is running is the water pump moving water (you should have water flow through the thru-hull fitting). Keep the functioning unit shut off while testing. Do you have a operations manual - it may list possible causes. When is the last time the unit worked normally? Could it be low on freon?

Found this exchange in the archives...hope it helps...

Assuming you have a Cruise Air SMX control, what you are seeing is actually LO PS (not P5) and it means 'Low Pressure'. This is most likely an indication of low freon.

From another site: LO PS (low pressure) loss of freon or can also be caused when the thermostat is set way low to cool and the manual override on the fan is also set way low not allowing enough air to get across unit and consequently it freezes up. Also note when we go from the fall to the first cool weather and you turn the unit on to heat it is not uncommon for the LO PS warning to come up. There is reason for this that is too technical to go into, but just let the system sit for a few minutes and turn it back on.
jg300da
02-27-2007, 11:20 AM

Could be as simple as a dirty filter which would cause a low back pressure.

Alex D
02-27-2007, 12:16 PM

If you are using the system to heat with ambient water temps being 40F or lower, this warning is indicating that the water temp is to low or your freon is low. This message does not neccessarily mean you freon is low!

If freon is low and as temps get colder the sytems cannot build as much pressure and magnifies potential low freon situation. SImply have the system checked and charged to capacity. IF you don't, you will most likely not even have a problem in the summer.

Sea Ray 300
02-27-2007, 02:07 PM

In reference to a dirty filter, you'll be amazed as to how quickly the filter gets dirty.
It's just a 10 minute job to rinse it out, and then you're as good as new... :thumbsup:

 

[katricol]

I think it is the trigger switch. It is a relay switch in the main, called a TR-115. If you open the main for your system,you will see 2 very "squiggly" lines to 2 switches. If you reverse them and then the aft heat works, you will know that is the problem. Easy fix.