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Cruiseair A/C behavior

  • Thread starter Thread starter Gusshr
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Gusshr

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  1. OWNER - I own a Hatteras Yacht
Hatteras Model
53' MOTOR YACHT (1969 - 1988)
The air conditioning in the salon is a 35 BTU reverse cycle cruiseair unit. It blows cold air however after working for long hours (variable 2-5hrs) cycling on and off to keep the room at a certain temperature it starts to behaves in a funny way. The compressor would turn on for five seconds and turn off for three seconds repeatedly. No error messages on the SMX II control unit to indicate HI PS. So I turn the unit off and then after a minute I turn it on and it would work normally again. The pump for the unit also cools down another two units in the engine room and it would be running normally when this issue happens (last time it was on because because other units had the pump on). I have a huge stream coming out on the side of the boat which tells me that the water flow is adequate, and also in the absence of HI PS error message tells me it is not a water flow issue. When this problem happens I point the laser gun on the unit itself and the maximum temperature I read on the compressor body is 160° which is within normal range as I think. I am thinking that the problem has to be related to a heat sensor problem. I don’t think this is a Freon problem because the unit cools down effectively before or after this on and off behavior. Any One has any idea about what could be wrong?
 
Could this be icing up? Is it possible for a unit to ice up even with the right size Freon charge in it?
 
I would check refrigerant pressures and see if it is really a high pressure issue or not. If pressures are fine then it could be a bad sensor or connection
 
Briankinley2004 said:
I would check refrigerant pressures and see if it is really a high pressure issue or not. If pressures are fine then it could be a bad sensor or connection
Click to expand...
Can I check the high-pressure myself if I have gauges? Where can I find the instructions about using those gauges?
 
You can but really need someone to show you what to do if you have not done before. My units have back seating valves which means when open all the way you won't get a pressure reading. You have to partially close the valve to allow for a pressure reading. Yours are likely the same. I have a chart that tells the proper pressures for a given water temp but it is too large to upload here. I would be happy to email it to you. If you haven't cleaned the heat exchangers I would do so even though you are getting good water flow. All of mine run on one pump and if one of the exchangers is clogged you still get a good flow through the thru hull. The water will just flow more through the cleaner exchangers more. Its good maintenance anyway.
 
Also once you have cleaned the heat exchangers drop a few bromide tablets in the strainer basket on a regular basis. this will help keep them clean. And when I stated a bad sensor above I was referring to the high pressure switch. I would not bypass it to test if you don't know what the actual pressures are. The gauges will tell you what you need to know but without them I would clean that heat exchanger by circulating barnacle buster, concrete etch/prep or similar using the Genisis method. It won't take you long and will probably solve the issue.
 
jim rosenthal said:
Could this be icing up? Is it possible for a unit to ice up even with the right size Freon charge in it?
Click to expand...
I did not see ice on the coils in the Engine Room. However one side was actually sweaty! What does that means?
 
Gusshr said:
I did not see ice on the coils in the Engine Room. However one side was actually sweaty! What does that means?
Click to expand...

A properly charged unit usually has sweat on the suction line at the compressor. If your evap coil was iced up a lot you would probably not have good airflow out of the vents. A unit can ice up with proper refrigerant charge. The cause would most likely be a faulty blower not moving enough air across the coil or a very dirty filter or evap coil. I wouldn't think high pressure cut out would be caused by an iced up coil. If the refrigerant charge were very low you would most likely cut out on low pressure fault not high. Again lacking gauges my first move would be to clean the heat exchanger to the defective unit since it shares a pump with other units.
 
Briankinley2004 said:
A properly charged unit usually has sweat on the suction line at the compressor. If your evap coil was iced up a lot you would probably not have good airflow out of the vents. A unit can ice up with proper refrigerant charge. The cause would most likely be a faulty blower not moving enough air across the coil or a very dirty filter or evap coil. I wouldn't think high pressure cut out would be caused by an iced up coil. If the refrigerant charge were very low you would most likely cut out on low pressure fault not high. Again lacking gauges my first move would be to clean the heat exchanger to the defective unit since it shares a pump with other units.
Click to expand...
I dont think I have a high pressure cut out issue. Otherwise I would get the famous HI PS error message. I am now remembering having this problem when I first got the boat and had an AC company try to troubleshoot and found nothing wrong. Thats why I think maybe I have an intermittent faulty sensor of some sort that does not give an error message like a faulty high compressor sensor Maybe I am better off changing the sensors rather than another costly troubleshooting. Are there any available diagrams of the circuit of the cruiseair units?
 
Sweating on the suction return line at the service valve is normal. Back in the day, techs would charge an ac unit until that spot was like a cold can of beer outside on a hot humid day.

When this happens is the evaporAtor blower motor still running or does that cut off as well?

Your certain that the water pump is running during the lead up to this problem?

Look at the evap coils/fins when then happens, are they icing up?

Shoot the compressor temp with you IR gun at the top over where the small tubing exits the can.

George
 
Thanks George.


When this happens is the evaporAtor blower motor still running or does that cut off as well?

The evaporato will follow the compressor on and off cycling as usual

Your certain that the water pump is running during the lead up to this problem?

Yes, besides that if it was a water pump issue the shutoff would happen few minutes later not few seconds later, and also you get the HI PS error on the screen ( I had another unit with the pump lossing prime on the way and these are the symptoms: first starts, then 3-5 minutes later gets the HI PS and shuts of and stays off "No Cycling")

Look at the evap coils/fins when then happens, are they icing up?


I did not do that, but if that was the case then it wouldn't take 3 hours to ice up, and it wouldnt go back to normal operation after I shut off and then few minutes later turn the unit on again.

Shoot the compressor temp with you IR gun at the top over where the small tubing exits the can.


Maximum I got was 161 degrees on the body of the compressor.


Gus
 
Sorry I mis-read. I thought it said you were getting the high pressure error. You really need to know your pressures but absent that who knows. Check for corrosion on the terminals in the control panel in engine room. Pull out the cables coming from temp sensor, display pad, etc and clean. You also could have a compressor going out on overload. Check the amps the compressor is pulling after it runs a long time, at start and once it gets going. As mentioned by others check air flow, evaporator coil icing, etc.
 
IMG_1356.webp

Ok. So I found the wiring diagram and here is my observation:

I have two sensors a start capacitor and a run capacitor.

Since there are no error messages on the SMX II, then that rules out a HI PS sensor problem. and also if it was a HI PS problem the unit will just stay off and cycle on and off every few seconds as I have.

I am thinking that the run capacitor is the culprit maybe it gets tired after few hours and fails to maintain the compressor on and thats why it shuts off and then few seconds later the compressor turns on again because the sensors are in an "ON-connect" mode and the starter capacitor enables the compressor to run but again after few seconds the compressor turns off again because the running capacitor fails to maintain the compressor and the cycling continues. I wish I can ask the manufacturer, any one had luck with tech support from cruiseair?
 
I always get great support from dometic. They are very good at providing their dealers with support and parts.
 
IMG_1354.webp

OK the black capacitor is the starter capacitor (see the green arrow pointing at the parallel resistor) so the silver capacitor is the running capacitor (white arrow), and looking at the connector in the circle I see corrosion, which makes me think of reason for the problem. I will be discharging the capacitor with some heavy well insulated screw driver, and apply some dielectric grease in there and maybe change the whole spade connector.
 
Dont bother. Replace both and the connectors. It's cheap enough and simple.

How much time have you spent chasing down the problem so far?

Without the right tools its impossible to do it efficiently. If theres no change after replacing the caps you need to monitor the sensor lines to see what's happening.
 
There are a couple of explanations for this behavior>

Your heat exchanger needs cleaning and has poor heat transfer from the high side refrigerant circuit. This is unlikely with a compressor can temp of 160F but make sure that you shoot the top of the can right where the hi side line exits the can.

The compressor is overheating for any number of reasons including seized bearings, etc. This would open the high temp switch on the side of the can which is an auto reset sensor. This is unlikely because it resets so fast and the evap blower also shuts off. This temp over limit switch merely interupts power to the compressor.

The water pump stops. This is unlikely because you get no hi pressure alert on the controller and because you observe that its working OK.

That leaves the SMX controller in the cabin or the control board/relay/capacitors in the condensing unit , or their cabling and connections. You should check all of the connections, plugs and cables. If nothing there then swap SMX controllers with another unit and see if the problem follows the controller. Thats easier than dealing with the control board in the condensing unit.

If that doesn't do it then we move on to the components in the condensing unit


George
 
Last edited:
You posted at the same time as I did. Since you started in the control box:

You can remove the capacitor and test their capacitance values. An ESR measurement is also good but most won'y have that capability. Is there any bulging or leakage from the caps? They are fairly inexpensive to replace and you dont need cruisair part numbers. I buy high quality replacements off the internet. Always use a high quality, USA made run cap like Titan. Shake the relay and see if anything is rattling around inside. Cleaning the connections is also a good thing. Why are they corroded? Look for water intrusion or leaking caps.

I have a technical contact at Cruisair. PM me if you want it.

George
 
BTW, if you do have a high pressure problem, the system will restart a number of times before it shuts down and then displays a code on the SMX.

George
 
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