"P5 LO" indication on AC/Heat unit

LLSEA

LLSEA

New Member
Feb 27, 2007
5
Chicago Harbors- Lake Michigan
On the hottest days of the summer the air conditioning in the cabin runs and cools the boat just fine until in clunks off and a "p5 Lo" indicator flashes on the AC/Heat control.

Does anyone know exactly what that is indicating? I was thinking possibly low coolant, but the system seemed to run fine and get very cool. I was going to have someone come out and look but don't want to spend the money if it is meaningless.

Any help is appreciated.
 
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.
 
Could be as simple as a dirty filter which would cause a low back pressure.
 
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.
 
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:
 
Sea Ray 300 said:
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:
Click to expand...
Are you talking about the sea water strainer or the air filter/mesh in front of the heat exchanger intake?
 
Alex...
The air filter in front of the heat exchanger...
An acquaintance burned out his air conditioner because he didn't know it was there....
I cleaned ours twice during a 5 month season...
Very similar to the filter on a window air conditioner.
 
Wow am I glad this question was asked. I had totally forgotten we started seeing this error message late last season. I just called the yard and had a freon check added to my work order.

-CJ
 
Do NOT use guages routinely to check refrigerant charge in these units. Instead use cooling effectiveness as your first indication of proper system operation. The amount of refrigerant used in these units is so small, usually less than 16 ounces, that the small amount lost during the attaching and unattaching of the manifold set is enough to greatly effect the capacity of the unit. In addition, because they hold such a small amount, usually any leak at all will result in very low or no cooling. Seeing as how the failure code in this instance came on after the cabin had been cooled, I doubt it has anything to do with refrigerant levels. More than likely reduced airflow caused by a clogged air filter.
Something else to be aware of, when the filter gets dirty, the water condensing on the evaporator tends to carry with it some of the trapped dirt, causing the drain line to get stopped up or the sump pump under your floor to get gummed up and stop pumping. Just another reason to clean the filter regularly.
 
i used to get the same error message sporadically. i had a marine a/c guy come down to check and he had no real answer, b/c, of course, it was working when he checked it. he did feel that it was a water flow issue, and he said it could be the pump. could also be a constriction or obstruction somewhere in the lines. i also had very weak flow at the forward overboard discharge but very good flow at the aft one.

so, the next time it happend (90+degree day of course) i disconnected the water line from the OUT side of the pump, climbed into a tube with a garden hose in hand, left my buddy in the bilge watching the disconnected water line, and shot water up into the forward overboard discharge. good pressure, good flow back at the pump. so no constriction. i took the pump apart and stared at it as if it would tell me its problem. when it didnt, i decided to replace the pump. seemed like a good idea anyway, since it was original equip in a boat which, at that point, was approaching 16 years old). lo and behold, end of problem. much improved overboard flow and no more error messages at the panel.
 
rondds said:
. .... i took the pump apart and stared at it as if it would tell me its problem. when it didnt, i decided to replace the pump. seemed like a good idea anyway......
Click to expand...


Now THAT was funny..... :smt043 ....I think starring at things is second only to smacking them with hammers and hoping for a fix.....thanks for the laugh......
 
It is always something on boats, is it not?

My 420's midcabin/salon Cruisair unit is displaying a LO/PS error code in heating mode after pumping warm air for an hour or so, and will also display a HI/PS error code when operating in A/C mode. This began shortly after we recommissioned. As the river water was still pretty cold (mid 40 degree range, I think) I discounted the LO/PS as caused by cold water; however, the forward Cruisair unit was, and is, operating properly. River water temperature is now easily above 50 degrees ( I know, I swam under the boat yesterday to check my props after yet another #$%^&*!! Potomac River debris strike.... and the LO PS and HI PS error codes still continue--I had occasion to try both heat and AC modes yesterday.

The forward cruisair unit, which relies on the same water pump as the midcabin unit to feed it cooling water, is operating fine. Water flow out of both discharge throughhulls is good. Filters are clean in both units.

My first thought is to reset the midcabin unit to factory default settings using the SMXir keypad. It is entirely likely that my two year old pushed a series of buttons and did something that is contributing to this problem. Unllikely, but possible.

My next thought is to go the freon recharge route, since these error codes can be cuased by "loss of gas"

Is the freon re-charge something a DIY rookie like me can do? Any other thoughts before I pay Cruisair to come all the way to Quantico from Annapolis?

thanks,
Skip
 
Dummy me

OK.....I gotta ask this because i dont know :huh: ......<BLUSH> :smt021
Where would the filter be located??? In the wall where the control thingy is?? :smt100 It never occurred to me there might be a filter....Man, I gotta check it.
 
It is right in front of the coil on the main unit. It slides in from the top. It is very thin web like material. Pull it out and wash it off. You should do this several times a season for best efficiency.
Mike
 
Skip said:
It is always something on boats, is it not?
Is the freon re-charge something a DIY rookie like me can do? Any other thoughts before I pay Cruisair to come all the way to Quantico from Annapolis?/quote]

I believe you need a license to buy freon due to the restrictions on its use. The licensed contrators use freon that is recycled from other jobs. At some point it will no longer be available. So...probablly not a dyi job.
Click to expand...
 
goblue, thanks. I re-posted this in the maintenance section and the consensus seems to be I need a freon re-charge and any HVAC tech can do it. I will post the fix and approx cost when we get it repaired..this week, I hope.
Skip
 
I had the same error messages in both heat and A/C modes as mentioned in this post after launching last weekend. Noticed that there was no discharge out of the front starboard side while unit was running. Initial thought was a bad water pump. After the parts guy quoted me $330 for a replacement pump, I decided to dig a little deeper before pulling out the plastic. Problem turned out to be a clogged discharge hose between the AC unit in the vberth and the front drain. Used compressed air to blow out the line and now I have a good stream of water being discharged in both modes. :thumbsup:
 
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