1500 Marina Bay Dr. Suite 1611
Watergate Yachting Center, Pier 23
Kemah, Texas 77565 USA
Phone (281) 334.1993
Fax (281) 334.4795

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YOUR BOAT Air Conditioning

Your A/C system is not like your system at home. Your home system uses air to cool the evaporator and your marine system uses seawater to cool the evaporator. This seawater cooled system consists of a thru hull a sea water strainer and a 110 vt pump. Problems associated with the system are generally associated with a clogged seawater strainer. And just like your home system you also have air filters that you should clean and check once a month.
The following is meant to be rough guide how to check both the a/c filters and the sea water strainer.

First I see the display and the vents in the boat but where is my A/C system located? Boats under 40' usually have one system. Boats over 40 can have 2 or 3 systems. Depending upon the system installed you could have 1, 2, or 3 thru hulls all with pumps and strainers. However with the right pumps you can run two A/C's off of one pump and strainer.

So to locate your systems. It's best to look for the return air grills. Take a look at photo 1.

Please note-Everything written here is meant to be a guide line. If you don't understand something consult a professional.

1) This return a/c grill is below a V berth . This grill has a mesh screen , which should be cleaned monthly.
2) This is the compressor for the return a/c grill at the left.
3) The water flows thru the compressor to cool it. Note this is the OUT side of the flow. This is important to know in case you ever need to bleed the air from the unit
4) This A/C grill is below a Settee. This grill has a mesh screen which should be cleaned monthly. Just remove it and hose it off.
5) This is the mesh screen inside of the return grill. Seen from the inside
6) The blower also has a mesh screen that should be checked and cleaned as well.
7) This is the same unit as photo #4 with the settee removed
8) This is the same unit (as #4) taken from above. This is a self contained unit . The compressor is on the left and the blower on the right.
9) Note the hoses coming in/out of the compressor. Follow the inside down into the bilge to find the pump, strainer and thru hull.
10) This is the A/C thru hull. It could be Marelon (a black plastic like composite material) or Bronze. Some like this one are marked with a tag also
11) A/C Thru Hull again. With the handle standing up or inline with the thru hull means it's open
12) Same Thru Hull with the handle shut off (across the valve). Let's check the strainer. So shut off you're a/c system, 12) then close this thru hull.
13) Follow the hose up from the thru hull and you'll next find the strainer. This strainer is plastic and just screws off. Some are also bronze (see picture 17) and open differently. All of them will have a strainer inside that will need to be cleaned.
14) Note this strainer can just be unscrewed by hand. (MAKE SURE THE THRU HULL IS CLOSED BEFORE YOU DO THIS. ) Most clogs are here. The strainer gets marine growth, debris, even small fish get clogged up in here.
15) What's pumping the water is the 110vt pump, seen in red here and hooked directly to the strainer. From the outlet at the top of this pump is the line that is coming into the inlet side of the compressor. Most pumps brands that are red are March pumps. The silver round ones are called Cal pumps. They both work the same way.
16) This is totally different boat and A/C system, but here you will notice two lines coming off one pump. That is to feed two different a/c systems off of one pump and strainer.
17) This photo shows a common bronze type strainer that is made by Groco. It opens from the top. There is another type of bronze strainer that opens from the top that just hast two wing nuts to open.
18) To open this type of strainer require a tool call a spanner wrench. It has two separating ears that go in 2 or the 3 holed tabs shown and you rotate counter clock wise to open. After opening pull out the basket and clean it.

19) Make sure after cleaning any strainer , you A) open the thru hull. B) check the strainer and hose clamps for any leaks C) after starting the a/c unit back up you look for water coming over the side.

So how do you know if the A/C system is working properly? When running, it should be pumping water over the side. Find the discharge side of the line leaving the compressor and find out where it goes out the side of the hull. When you turn the system on and the compressor kicks on a few minutes later, you should see a stream of water going over the side for EVERY unit you have. You should make yourself familiar with where the a/c waters exits the boat.

More than likely you're going to come down to the boat one day and the A/C will be off and the display will be flashing HI PS. This means High Pressure and generally means the water flow has been interrupted to the compressor and senses this the compressor shut itself off. Once in awhile a fish or plastic bag can just get up against the thru hull and shut water flow off and consequently shutting the system down. So you can try to restart the system but if you don't see water streaming over board, you're going to be better off just shutting the system down and checking the strainer as we have already explained.

After clearing the strainer. Make sure you turn back on the thru hull before starting the A/C system. Then after starting make sure you check for water flow over the side. It may take a few seconds before it starts a steady stream but you should see something coming out. If not. Then the clog is not cleared or it could be further up the pipeline from the strainer.

In this case, you will have to go back and troubleshoot the system. Start back at the strainer. Is it full of water or air. If it's full of air, crack it open and bleed the air out by leaving the thru hull partially open. Then re-secure the strainer, reopen the thru hull fully and try again.

Still no water? When the compressor kicks on the pump also kicks on. You should hear it running or be able to feel it vibrate. If it is not you're pump is probably bad. It's best then to stop here and call for some professional help unless you feel confident you can change out the pump.

The strainer is clean, full of water, the pump is definitely running, you even hear water gurgling in the strainer and pump, but still not water. You still have two more solutions before quitting for good. The unit is probably air locked meaning the pump pumped all the water out of the compressor when it got blocked. Turn the unit back off. Find that outlet line on the compressor. See photo 3. Usually it's a simple 1 or 2 hose clamps. Loosen that hose clamp enough to where you can slip the hose on and off. Now get a buddy to turn on the a/c. (NOW CAUTION- You are about to have a 500 gallon per hour pump pumping salt water at you thru this hose you just disconnected and also possibly all over a 110VT (READ POSSIBLE ELECTROCUTION) Compressor. Only do this if you feel confident that you can do it. The pump should come on and at the same time you should have the hose just partially off the nipple on the compressor. Just enough to let the air that the pump should now be pushing out. If this is now happening then the water is coming real soon and as soon as it does, make sure you've got the hose back on and then tighten up the clamps. Maybe even have your buddy shut the unit off before tightening the clamps. Do not leave the unit running without the clamps tight as the pressure can blow the hose off.

Get everything tightened up, and turn the unit back on. Now do you have water coming out the side? If so, is the unit cooling? If so you're done.

If by chance this didn't work, you still have one other solution. The pump has a hard impellor in it. When the water stops flowing the pump gets hot and sometimes it will seize to the walls of the pump housing. The pump can sound like it's running and still not be turning the impellor if it's seized. Go back to the pump. Disconnect the outlet size hose clamp and remove the hose. Have your buddy turn on A/C. If the pump is running and nothing is coming out try tapping the housing (On a red March pump the housing is also plastic, so tap light) with something. If it's seized this may just break it loose. If it does and starts pumping. Shut everything back off. Hook it back up and also figure that you may have to bleed the unit at the A/C compressor outlet again.

If none of this works, you probably should call one of local area A/C fellows to help you with the unit.

A few notes. If you have the more modern Cruise Air SMXII a/c system, the unit is quite smart and will display to you warning signs to tell you what is wrong.

HI PS (high pressure) means loss of water flow
LO PS (low pressure) loss of freon or can also be caused when the thermostat is set way low to cool and the manual override on the fan is also set way low not allowing enough air to get across unit and consequently it freezes up. Also note when we go from the fall to the first cool weather and you turn the unit on to heat it is not uncommon for the LO PS warning to come up. There is reason for this that is too technical to go into, but just let the system sit for a few minutes and turn it back on.

Remember that the unit is going to cycle 3 times before any displays for HI or LO PS come up. There is also a setting for low or loss 110vt voltage that will come on anytime the voltage has dropped.

To turn on the dehumidifier you hit the COOL, HEAT, FAN buttons at once.

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