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Cruise air intermittent
August 8, 2010
7:35 am
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Steve Pooler
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Forum Posts: 1127
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November 12, 2008
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Geoff,

Most all A/C pumps have hard impellers & are not self priming if installed incorrectly...These type pumps draw less amperage and are much quieter & durable than a rubber blade impeller pump.

Changing the pump is not the answer...Finding why this one won't prime itself is.

If this pump is sucking air...Any new one will too...Aerated water is not a very good cooling medium, and that is what will be sent to the a/c, so it will work harder with aerated water.

Some things to look for in your plumbing....

  • Look for a constant uphill run from thru-hull, to strainer, to pump...with no hose dips or loops.
  • All three of the above must be mounted below the water line...No hose between should rise above the water line either.
  • If you have the Perko strainer with two wingnuts for checking the basket...Be sure those nuts are tightened evenly...With that strainer it's easy to get the cap cock-eyed...Also be sure the cap gasket is good...Some were cork & wore out easily.
  • Be sure there is a forward facing scoop over the untake on the hull...If not...The Venturi effect of the water passing by at 8 knots or above will pull the water out of the pump.

If you post a picture of your installation I may be able to be more specific...

Steve~

August 6, 2010
8:20 pm
gdsimmons
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Guests

Steve,

I have determined that the pump is indeed losing prime. The pump currently in th boat has a hard plastic impeller so I belive it may not be self priming. Can I use any pump of equal gal/min or does it have to be specifically for the A/C system. I looked at a couple at West Marine and they were self priming 20 - 30 gal/min at around $100-$130.

Again I really appreciate all of your advice.

Geoff

August 4, 2010
9:02 am
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Steve Pooler
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Forum Posts: 1127
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November 12, 2008
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Geoff~

There should be nothing but hose between the pump output & the A/C inlet....Your problem has to be in the plumbing, thru-hull, or the pump...Maybe sucking air and causing the pump to loose prime...The A/C unit is just shutting itself off as a protection.

Shut everything off & look for leaks...These leaks will suck air when the pump is running...

August 4, 2010
8:41 am
gdsimmons
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Guests

Steve,

Is there an internal automatic valve somewhere in the system after the pump. If not I will assume that the pump may be the culprit. Can I troubleshoot this by hooking the compressor up to shore water and running the ac that way to ber sure it is indeed the pump or a clog prior to the compressor? Is there any possibility of damaging the system by doing this?

Thanks again, Geoff

August 4, 2010
7:37 am
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Steve Pooler
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Forum Posts: 1127
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November 12, 2008
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The A/C will not run without water....True that is a Consistant...Or Constant....Either Way...No Water Flow...No A/C !

I'm not there to see why you loose water flow, and really can't say from here...But one thing is for sure...You will consistantly loose A/C if you don't find your water problem.

Steve~

August 3, 2010
10:27 pm
gdsimmons
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Guests

Steve,

We have a '75 Trojan F36 Tri Cabin. The cruise air has been working on and off. I cleaned the strainer and checked the pump and it seems to be working good, in fact the pressure out of the side of the boat was the best I have seen. The air worked for several hours and then the flow stopped. The pump was still running and the compressor was cycling on and off. This problem is very consistent in that after the system runs for a while the flow will stop and the compressor will cycle on and off.

Any advise is appreciated.

Geoff