AC problems

Phasma

Phasma

Phasma2128
Sep 17, 2016
691
West Michigan
Boat Info
2003 360 Sundancer
Engines
Mercruiser 8.1s Horizon
Scratching my head….
about 3 weeks ago my salon Cruisaire stopped working on my 1993 48 cpmy. The two dometics for the cabins are still working. The salon AC kicks on but doesn’t cool. It runs for about 30 seconds and kicks off. It then kicks on again for 30 seconds and gives me the Hi PS error on the SMX ir. Reading all that I could find I understood that the water flow through the system was probably blocked. It is a single pump for all 3 units. As I said the two dometics work fine. Comparing the discharge from the side of the boat to my neighbors Bertrand it is about 50% what his discharge is. This all happened about the same time I upgraded my sound system at the helm. The cooling part of the system is under the helm and the compressors are in the engine room.

I disconnected supply and drain hoses, connected a garden hose and back flushed the system. A large amount of black gunk came out of all 3 units. I reassembled everything and tested the system. The same exact error code…. Air flow through the salon seems adequate. I pulled the salon return air filter and cleaned it. I also pulled a large amount of sea weed from the sea strainer and flushed the thru-hull. I connected the pump directly to the discharge line and the discharge did not increase. Pulling the pump apart it doesn’t look like the impeller is bad. The motor was a little hot to the touch.

My thinking….: If it were the high preassure switch that is bad, wouldn’t it still cool until the pressure built to the shutoff level? Should I jumper across the hi-pressure switch and test? Would loss of R44 cause this to suddenly happen? Replace the pump and motor?

Any ideas? Any help would be greatly appreciated….
Martin
 
If the compressor starts and shuts down on HI PS then nothing wrong with the head pressure switch. It is still not transferring heat to the raw water. There is blockage in the water path or a buildup in the heat exchanger loop.
 
Two units work one does not, unlikely the water pump itself.
Loss of Refrigerant will cause evaporator icing but not a Hi PS trip, it would be a Low Pressure trip.
Since you got crude out of the raw water side, a good followup flush (bleach or barnacle buster type flush) wouldn't hurt to clean of the tubes.

Also check your hose routing air trapped in the loop can slow water flow and limit cooling ability. Water goes in low comes out top. The discharge hose to over board must run flat or very slightly above the unit (to allow air to vent easily).

But 30 seconds is very fast to build high pressure. It could be a weak HP switch that is tripping early, pretty easily to change that.
 
Would bypassing the hi pressure switch temporarily to troubleshoot be worthwhile?
 
Phasma said:
Would bypassing the hi pressure switch temporarily to troubleshoot be worthwhile?
Click to expand...
Without having a set of gauges on it to watch the pressures it would be a risk.
 
Phasma said:
Scratching my head….
about 3 weeks ago my salon Cruisaire stopped working on my 1993 48 cpmy. The two dometics for the cabins are still working. The salon AC kicks on but doesn’t cool. It runs for about 30 seconds and kicks off. It then kicks on again for 30 seconds and gives me the Hi PS error on the SMX ir. Reading all that I could find I understood that the water flow through the system was probably blocked. It is a single pump for all 3 units. As I said the two dometics work fine. Comparing the discharge from the side of the boat to my neighbors Bertrand it is about 50% what his discharge is. This all happened about the same time I upgraded my sound system at the helm. The cooling part of the system is under the helm and the compressors are in the engine room.

I disconnected supply and drain hoses, connected a garden hose and back flushed the system. A large amount of black gunk came out of all 3 units. I reassembled everything and tested the system. The same exact error code…. Air flow through the salon seems adequate. I pulled the salon return air filter and cleaned it. I also pulled a large amount of sea weed from the sea strainer and flushed the thru-hull. I connected the pump directly to the discharge line and the discharge did not increase. Pulling the pump apart it doesn’t look like the impeller is bad. The motor was a little hot to the touch.

My thinking….: If it were the high preassure switch that is bad, wouldn’t it still cool until the pressure built to the shutoff level? Should I jumper across the hi-pressure switch and test? Would loss of R44 cause this to suddenly happen? Replace the pump and motor?

Any ideas? Any help would be greatly appreciated….
Martin
Click to expand...

Sounds to me like you need an muratic acid wash to clean the scale off the heat exchangers. Just to do a quick cleaning suck out the water from the strainer; fill with what ever acid you think fits the bill (add a squirt or tow of dish washing soap. Makes for a suds in the out flow so you can tell where the acid is in the system ); open the throw hull and allow the pump to run just enough to pump a little of the now diluted acid solution through the system; let the solution sit in the ac plumbing system 10/15 minutes; lastly turn on the ac system and see if the system is good to go.

If this made things better then go get a full blown ac system flush. I posted how to flush an ac system as well of how to make a acid flush canister.
 
The system is now fully flushed. I made a 50/50 solution of water and muratic. I ran it through the system for 30 minutes closed loop. Lots of nasty crap came out. I reconnected all hoses and put the system back together. The problem remains….It runs for about 30-45 seconds, shuts off, restarts for another 30-45 seconds and throws the Hi Ps error on the smx control….I’m stumped

I still question the amount of water being discharged. Would an inadequate amount of water through the system due to an under performing pump cause the Hi Ps error?
 
If you are going to throw parts at it the pressure switch is the cheapest.
To really diagnose whats going on you need AC gauge set and hoses.
 
Have about 48 hours to figure this out myself. I have an appt Monday morning for a pro to come in
 
hughespat57 said:
Two units work one does not, unlikely the water pump itself.
Loss of Refrigerant will cause evaporator icing but not a Hi PS trip, it would be a Low Pressure trip.
Since you got crude out of the raw water side, a good followup flush (bleach or barnacle buster type flush) wouldn't hurt to clean of the tubes.

Also check your hose routing air trapped in the loop can slow water flow and limit cooling ability. Water goes in low comes out top. The discharge hose to over board must run flat or very slightly above the unit (to allow air to vent easily).

But 30 seconds is very fast to build high pressure. It could be a weak HP switch that is tripping early, pretty easily to change that.
Click to expand...
Most of the units I’ve worked on ignore the high/low pressure switches for the first 30 seconds of run time.
 
New impeller this morning. The old one was not broke or appear worn but I replaced it anyway. The unit runs longer before throwing the error code. I triple checked the sea strainer and all is clear. When sea strainer was open I opened the sea cock and a solid flow of water came through. I am still puzzled by this. I did notice that when cool is selected on the smx, the display says cool but it no longer says cooling
 
When you say the system is fully flushed… have you disconnected the line at the manifold and flushed just the loop that goes to that unit? You cannot tell where the water is flowing from looking at just the discharge unless each unit has its own discharge. I think the hose going to this particular unit is clogged.
 
Easiest test for flow is to drag a garden hose into the boat and connect it to your inlet side of the cooling loop. Crank on the hose to full power from your dock water and then fire up your AC unit to test it. If runs fine then you know it is a supply problem because your pressure will be higher with the garden hose than your 3 way split pump. I just did this to mine as I am having the same issue with the forward state room AC now that it is hot as balls in South Florida. I am upping my pump size to solve this issue. You can see more on the 48Da thread.
 
Have you cleaned the coil good, low airflow can cause this to. Just went though both of our Pompanette units.
High head trips

Strainer cleaned- that's every week ot two this time of year in Savannah.
Coils thoroughly cleaned and flushed-twice
Backflush heat exchangers

Got 63.2 degrees at register 90 degrees that day.

Good luck
 
DO NOT USE MURATIC ACID! That is straight from the a/c pro that works on my units. It will ruin the units. Use barnical buster.

Call a pro to work on the unit and don't throw parts at it.
 
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