AC fails - HI PS only when underway

W

WFYB

New Member
Oct 5, 2006
143
Ft Lauderdale, Fl
Boat Info
500SD
Engines
QSM11
We are chasing a tuff one. My 3 port AC units are shutting down with a HI-PS code only while underway. The units are working fine at the dock. Plenty of waterflow at the dock. I have already taken the following action:

1. The strainers are clear.
2. I have removed the intake hose from the through hull it is free of any obstructions.
3. The diver has inspected the intake grate, there are no obstructions, shells sand etc blocking the intake. There are no hull mounted ducers to break up the water flow and introduce air into the system.
4. The entire system was acid washed and a new pump installed as part of the delivery punch list.

Again the system works great at the dock, all three A/C units blow plenty of cold air. The port sytem, (bridge) works fine while underway.

Any ideas where else to look
 
Do you have a grate over the intake? Could it be installed backwards? We had this happen only once when under way. There were very high seas and we rocked far enough to allow water to drain out of the intake line which introduced air into the system.
 
Are you getting AC power, from the Gennie, to the raw water pump? Try running from the gennie at the dock.
 
Your strainer for the AC cooling pickup may be coming out of the water (or exposed to air/water turbulence) while underway and losing it's prime. This will allow air to pass through the line and deny cooling water to the AC unit and cause the error message you are getting.

This can also happen when running a generator while underway, although the generator intake is usually located farther aft.

Just a thought but you may want to have someone watch the cooling stream from the AC units while underway and look for any difference from what it is while at the dock.

Good Luck!
 
You've done a good job of troubleshooting so far, the two suggestions above are all I can come up with as well.
As far as losing prime on plane; could be; is the boat "new to you",or have you been operating it for some time before this problem surfaced? If the A/C had been running fine underway, and now does not, it would be unlikely that airlocking would "suddenly" become a problem when it wasn't before.
Please elaborate on the timing of the shutdown. You say when "underway"- does this mean when you're at idle (and running the gen)soon after leaving the dock (how soon?), or do they shut down only once you're on plane (again- how soon?)?

I have one pump that serves two units; if you have separate pumps for all three units, it would seem very unlikely that all three pumps would airlock at the same time and shut down. That would seem to point to a voltage/generator issue. As mentioned above, do they run fine for a prolonged period under generator power while at the dock?
 
osd9 said:
Are you getting AC power, from the Gennie, to the raw water pump? Try running from the gennie at the dock.
Click to expand...
What?.......umm.....What....um..are you seriouos? Genny is running fine. Starboard air conditioning is fine. At the dock all is fine. Only issue is as they are making way the port air conditioning is not getting enough water. Most common cause of a P5 code is a clogged strainer. This has been checked and it’s clear.




OK, here is my question. Has it ever worked? Sounds like its a new boat for you.

It’s possible that someone added something and needed to move the location of the thru hull water intake before you purchased the boat and its now in a location that will get air when on plane. It’s also possible that Sea Ray did a brain fart and put the intake in a bad spot.

I think John’s idea is the best. Check to see if the grate is backwards. It’s the most economical thing to check next.

If you are at all wits end, try adding a water scoop under the hull. Water scoops are a big no-no on generators but sometimes they are used for air conditioning units. Actually, I’d like to hear what Frank says, he is good at these things.
 
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Presentation said:
What?.......umm.....What....um..are you seriouos? Genny is running fine. Starboard air conditioning is fine. At the dock all is fine. Only issue is as they are making way the port air conditioning is not getting enough water. Most common cause of a P5 code is a clogged strainer. This has been checked and it’s clear. ...............
Click to expand...

Yes, I am serious!

Where does WFYB say that the Genie is running fine and supplying good voltage to "ALL" systems on "BOTH" sides of the AC grid/panel?

A very plausable cause of HI PS codes is "NO" water flow, not necessarily "low" water flow....... On vessels with multiple AC units, using a single a/c AC raw water pump, 'Triggers' comes to mind!

Runs fine at the dock....while plugged into shore power? Port systems works fine....is the port a/c AC raw water pump wired to the 'opposite' side of the AC grid as the stb a/c AC raw water pump?

I don't see where you think it is obvious that the genie "isn't" a potential cause.

Way too many unanswered questions.......
 
Thanks all for the input. Let me add some additional information:

1. The boat is new to me. The boat sat at the dock for an extended period of time prior to sale. During survey it was noted that the three port side A/C units and the starboard bridge unit were all faulting with the High-PS. MMax had the boat serviced by an A/C guy who acid flushed the entire system and replaced the port side pump.
2. The A/C systems work flawlessly at the dock, at idle speed and low speed. The system faults to high-ps when on plane.
3. The intake grate is not on backward. The grate is open and unobstructed.
4. It is difficult to tell but water flow appears to be the same at cruise as at the dock. Again difficult to accurately tell as the flow is getting blasted toward the stern.
5. The systems run flawlessly on the genny at the dock. Ran for hrs when we lost power in the Abacos.
6. No changes were made to the intake and/or the location of the through hull when the boat was serviced for delivery.

MMax is going to send their A/C guy back to the boat. I sure would like to help point him in the right direction.

Thanks again for the help
 
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OK,

A few things to consider: You mentioned a new pump has been installed. 1.) Make sure this is the correct pump. Examine the outlet flow, you should have a good flow rate, almost separating into two streams out of the hull showing from port side with some also coming out of starboard side as well. 2.) Also have diver look underneath suction grate as I had an oyster growing in mine. I still suspect something is disrupting flow while underway. If possible look at through hull flow while underway.

Mark
500 SB Owner, Wrightsville Beach, NC
 
WFYB said:
Thanks all for the input. Let me add some additional information:

1. The boat is new to me. The boat sat at the dock for an extended period of time prior to sale. During survey it was noted that the three port side A/C units and the starboard bridge unit were all faulting with the High-PS. MMax had the boat serviced by an A/C guy who acid flushed the entire system and replaced the port side pump.
2. The A/C systems work flawlessly at the dock, at idle speed and low speed. The system faults to high-ps when on plane.
3. The intake grate is not on backward. The grate is open and unobstructed.
4. It is difficult to tell but water flow appears to be the same at cruise as at the dock. Again difficult to accurately tell as the flow is getting blasted toward the stern.
5. The systems run flawlessly on the genny at the dock. Ran for hrs when we lost power in the Abacos.
6. No changes were made to the intake and/or the location of the through hull when the boat was serviced for delivery.

MMax is going to send their A/C guy back to the boat. I sure would like to help point him in the right direction.

Thanks again for the help
Click to expand...

Thanks for the additional info...clears up some stuff.

You said that the tech replaced the port a/c AC Raw water pump. Do you know why? Was it completely dead or confirmed/suspected of low water flow? A long shot, but sometimes even new pumps are bad.....I just went through that with my fresh water system....brand new pump out the box had a bad pressure valve.

Also, where are the stbd and port raw water intakes located on the underside of the hull.....are they both at the same distance from the transom? It could be possible, as stated above, that the port side is just a little forward of the stbd intake and just on the hairy edge of not getting enough water while on plane......you could try running with full tabs down to drive the bow down and see if the problem goes away.

Good luck and keep us posted.
 
I would buy a length of clear heavy duty plastic tubing (sold at depot or lowes) and TEMPORARILY replace the black marine grade hose from the strainer to the pump with the clear one. Run the boat on plane and keep an eye on the tube. If you see air bubbles or a siphoning effect, you know it's possibly a flow problem. If the water stream looks clear from the dock, low speed and at cruise speed, it's probably not a strainer/water flow issue. Maybe electronic instead.

Obligatory Safety Note. The plastic tubing is not marine grade. Be ready to shut the valve off should something go wrong during the visual inspection. Do not run the AC without someone keeping an eye on the tube. Replace asap after test complete.
 
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How about deck angle?

A weak pump may not be able to pump the water uphill well enough while under way. I'd focus on the pump output.
 
Based on your updated info,
We know it can't be electronic in nature, 'cause the controllers have no way of knowing if you're on plane or at idle.
We know it's not electrical 'cause they run fine off the gen (until you get on plane).
All three units give you the same fault code, so it's *probably* safe to assume that the same problem is occurring with all three. I have no idea if a High-PS fault code could mean anything other than inadequate cooling water flow- what does the manual say?

Just a WAG, but two things come to mind:
Didn't work at time of survey; if it was a bad pump, it could have been replaced with a bad pump as noted above, or perhaps a pump with inadequate capacity. My 600 gph pump went up a few weeks ago, and I replaced it with a 1200 gph pump. Can't have too much cooling water flow...
Could also be some sort of factory problem- such as an incorrect scoop location, or incorrect size of thru-hull. I'm curious as to your setup- you have three (3) A/C units served from a single thru-hull and single pump? I have two units served from a single, and I doubt the 5/8" hose from the pump could handle enough volume to serve a third unit. I would have the tech consider the size/capacity of the thru-hull, hoses, and pump to verify that it can handle the total flow required by the three units.

This is a tough one- good luck and let us know how it goes.
Maybe we should all kick in a few bucks with the pot to go to the one who guessed it right :)
 
I don't mean to misdirect, but you might consider an acid flush. We have four a/c's.They all run on the same pump, but the forward stopped working. A quick flush and it worked fine. This was posted earlier. I realize yours is working at dock, but if there is blockage, there may not be enough pressure to push passed a partial blockage while underway.
 
A/C guy should be back at the boat over the next few days. I'll post his diagnosis. Thanks again for the great input.
 
3 units off one pump is not a problem. If all 3 units work fine at the dock and not underway the only common thing is water flow. AS said it can be disturbace of flow ... but for a lock out condition the unit will restart 3 times before locking out . So either the pumps stopping ... or something is blocking flow. As stated someone watching the discharge of water would a help. This is tricky. ( all 3 units are cutting off correct ? )

Rob

Rob
 
A voltage issue would give a different error code....

It would make sense that its an electrical issue. the a/c units draw the most and are the most sensitive to voltage. If the gensets acting up it would effect all 3 . The a/c units do have a low voltage shut down. The electrical distribution panel should tell of an issue. Run the genset at the dock for an hr.... fully loaded ( EVERYTHING ON ... EVERYTHING ) see if that frigs her up...

Gary might be on to something

rob
 
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