Lo/PS fault running heat, no fault on A/C

[jtingram2691]

So I recently switched all the cabin units over to heat now that its starting to get cold at night here in Virginia Beach. All the units run fine except the main salon unit, where I am finding a Lo/PS fault when I return to the boat in the mornings.

The owner took a short trip over the weekend and noted it had tripped a couple times, one of which was when he was returning to the slip. He claims it had a Hi/PS fault (but I'm fairly certain it was another Lo/PS fault ).

I have yet to see it trip as it seems to mainly occur at night when its cold, and I have not been able to get it to trip during the day when I set it to 90. Running the unit on Cool is fine. I have checked water flow on the condenser unit, pipes are not frosting over, no unusual sounds, etc.

I flushed the system about a month ago, and just blew out the unit today but nothing came out except water. Also blew out the handler drain hose just in case. In the morning I plan on checking the AC raw water pump impellers just to be sure of proper water flow (owner says they are 'relatively' new). I'm inclined to think they should be fine considering no other unit is tripping up, but I want to make sure I am covering all my bases before I call the A/C tech to come out again.

Anything else I should check or have overlooked in trying to diagnose/troubleshoot?

 

[racclarkson@gmail.com]

It’s likely one or both of two common issues. First likely is low on gas-cools fine but cycles on heat. Second likely is not enough air handler flow. That could be insufficient return size, clogged filter, clogged evap coils or a wearing out motor. You can select a higher fan speed as a first action. Unlikely it’s water pump if units work on cool.

 

[jtingram2691]

I clean the filters throughout the cabin monthly, and didn't notice anything in the grill earlier when I opened up the compartment. We had the condenser levels checked towards the end of the summer season, and everything checked out at the time (I'm hoping its not the issue, but very well could be). I'll try and clean the coils and see if that prevents the fault from occurring. I've also seen that another cause might be a frozen reversing valve, so I'll be checking that as well when I get the chance.

 

[Guy Walters]

This is such a timely post. I just got off the phone with my AC guy with the same problem. He and Robert are on the same page. He said that at this time of year as the water temp. starts to cool he in inundated with calls regarding the PS/LO code. His suggestion, like Robert's is to run your fan on high both for heat and cooling. I had turned all of mine to low speed just because I really didn't need very much of either. I think this led to the master state room's unit to freeze over resulting to wet carpet. I was very pleased that he gave me the information over the phone without a trip to the boat and saving a service call. It is worth trying.

Guy

 

[JD5652]

Here's an excerpt from the manual...

 

[Lmcruiser]

Had a similar experience this summer but on cool. Hot and humid day in July. My wife had turned down fan speed in master stateroom. Unit cycled off with ps/lo code on smx keypad. Turned unit off for a while and called to see if I could get ac tech. Meanwhile read online. Same suggestions. Turned unit on, turned fan speed to next to high in master state room and forward birth and no problems since even when we switched to heat this fall. I think in my case it was just the low flow of air over the coils that caused the problem. This is a 16K split system that services forward and aft mater staterooms.

 

[jtingram2691]

Ended up calling the local tech to come take a look, the problem was low gas. Topped me up and haven't had any problems since. I thought this was the issue, but wanted to exhaust all DIY solutions before calling them out here.

 

[Guy Walters]

High fan setting did NOT solve my problem either, so I also had to call my tech man. I had a faulty pressure switch. He changed that out and the unit is working fine.
Guy