High head pressure (HI/PS) error

[hperros]

I have a Dometic Cruisair system, and after running it for about 9-10 hours it shuts down with the HI PS error. I have cleaned out the air filters and the sea strainer, but the problem continues. The water pump does not feel hot when the error occurs. The system restarts after some time. Any ideas?

[Capt. Nini]

Try disconnecting the hose from the sea strainer to the pump and connecting a hose to it and flush out the system under pressure.
I have had to do this twice in 13 years. Especially bad in areas of high algae growth.

[digitalvillager]

If you are keeping the thermostat set below 70 and the seawater temp is above 85, you will have this problem. If this is the case, move your thermostat up to 75 and then after your 10 hour threshold, try moving it down to no lower than 73.

[hperros]

Thanks for your suggestions. I also talked to an a/c guy and he said that it maybe the head pressure switch, if the pipes are not frozen when the error occurs. Anyway, I have plenty of ideas to try out next time I go to my boat.

[hperros]

This problem was finally fixed, and I thought I would post this to the forum in case someone may have similar problems. I tried all the remedies to make sure that water and air was not being blocked, but It kept giving me the same HI/PS error at random times. However, after turning off the system, it would restart immediately. This went on until a month ago when it gave up. That is, it would start, run for a couple of seconds, and then display the HI/PS error and quit. If I turned it off and then restarted it, it would do the same. I was advised to replace the water pump (which costs $450 !! - I don't know why it is so expensive), but it turned out that it wasn't the pump. So, I had to call the experts. The a/c guy hooked up the system to his computer, and could not find anything wrong after much searching. He was about to give up, when he discovered that a red live wire had melted on another wire. I am afraid he did not explain to me on the phone which hot wire that was. Apparently, it was not a wire that one can spot easily. For some weird reason it gave the HI/PS error. So, a happy end after many billable hours .. and a working water pump I don't need. Looking back, I could have avoided getting a new water pump, by hooking up the pump directly to an ac plug and observe if water was coming out of the boat. Unfortunately, I did not think of it at that time. Anyway, you cannot always win!! If anybody wants a second-hand pump, please let me know.

[Airnsail]

I am a new owner from last April. The boat has been on the hard getting a new bottom job in Florida. Now, back in the water I am getting the dreaded HPF error. I have read the manual and followed all the suggestions here. I made sure the pump is primed, disconnected the output hose to make sure the pump is working. I even ran a a water hose directly to the unit from the output connection. I am still getting the error. I am at a loss as to what to do next. Nothing comes out the boat thru hull. Strainer clean, pump works great. Thoughts on wet heat I should do next?

Thanks.

Mike

[wolfe10]

Mike,

Try reaching over the side of the cockpit and sticking a hose into the outlet for the HVAC. Yes, with thru hull in bilge (inlet) open. Do that for 4-5 minutes and retry. Basically back flushing the system to eliminate any blockage and/or air locks.

[KenKrawford]

Just to be clear, you ran a garden hose (bypassing the water pump) directly to the AC unit and still didn't get any water coming out of the AC discharge thru hull? High pressure errors are almost always from a lack of water flow through the unit. You must have a blockage somewhere between the pump and the coils. AC water pumps tend to be a relative low output, low pressure type of pump. You may still have some discharged from a failing pump but now enough to cool your system properly.
My AC water pump failed several years ago and until my new pump arrived I was still able to operate the system by using a garden hose supplying water to the condensing coils.

[TBOT422]

It sounds like the unit is clogged if you are not getting any discharge out the thru hull on the starboard side. I had this a couple of years ago, however I was able to get some very small flow by attaching a garden hose directly to the AC input side. Our raw water intake is equipped with a Y-valve between the seacock and the raw water pump to allow flushing the system occasionally with fresh water via direct connection of a garden hose bypassing the raw water pump. If your system has been sitting on the hard with salt water in it for some time, it is likely clogged up. With just some minimal flow, I was able to fill a small bucket with Barnacle Buster and use a transfer pump to pump it into the AC unit, then let it set for a hour or so and flush thoroughly with the fresh water garden hose. Since then all has been fine. However, if you can not get any flow at all through the unit with the pressure from a garden hose, I suspect more drastic measures will be required.

Good Luck

[wolfe10]

That is why I recommend BACKFLUSHING IT (hose in the outlet which is starboard aft). Easy if on a floating dock and/or if you have long arms and reach over the side of the boat.

Have done that when seaweed got into the inlet and also after sailing in rough conditions where the inlet likely was briefly exposed to air and got an air lock.

[Airnsail]

Well, finally got the AC working.Took an old style (old style round screw type) and put it up the outlook hole. Some debris did come out. Then went back inside and stuck that nozzle back in the house past the pump. It fit perfect. That forced enough pressure thru to push the rest of the debris out. Now works like a charm. Thanks for the help and suggestions.

Mike