AC water pump not priming

[BillBerner]

I hope that's the right description. Maybe vapor lock is better.
Frequently, thoiugh not always, In order to get it to pump water, I need to disconnect the hose from the inlet at the compressor (heat exchanger?). That gets the water flowing. I reconnect the hose with water pumping, and all's good, but it's a PITA.
Any suggestions?

BB

[leigh weiss]

I added a water filter inline with the input of the pump. My boat did not come with one. I found it best to bleed the pump at the outlet of the pump to remove all air from the water line. If air gets into the system it could come from a small leak on the suction side of the pump or the pump seal. I assume you have looked closely at the pump and all the fittings for a "small" leak.
I does not take much air in the system to give you grief!
The inlet strainer on the outside of the hull has small holes (a screen) to keep out large junk. Check that the buildup of bottom paint has not restricted it causing increased suction and hence a suction leak only when the pump is running This would not leak water but would allow air to enter the system.
Keep us posted.

[MarkElliott]

So how do I reliably get the pump to pick up prime? opened the line from the seacock to do winterizing and pump will not prime to pull up antifreeze, even with a 3 ft line with the funnel filled with antifreeze attached to raw water filter to get some head pressure the pump. The pump should be active when ever the unit is working, heat or cooling, correct? Spec replacement pump says it is self priming. Had a steady stream going overboard in heat mode 2 weeks ago, now cannt get it to pump a drop. Frustrated.

[KenKrawford]

Mark, it's possible that your pump is shot. I had to replace mine after 4 years of light use. What brand /model do you have? I l looked into replacing just the impeller but it was nearly as much as a new pump. That pump should have no problem drawing fluid from a line that short.

[Salorboy]

I had the same problem with my A/C water pump. It would not prime when put in the water in the spring and ditto when trying to winterize. Found out from the previous owner that he had put a fitting in the line to resolve the problem which fitting was removed at some point prior to my purchase of the boat. My solution was to reinstall a fitting. I disconnected the intake from the thru hull at the inboard end of the water strainer and inserted a three opening valve with a female hose fitting. To prime the pump in the spring after launching the boat I attach a hose to the fitting, open the valv e and turn on the water and the A/C. Once the overboard discharge begins I close the valve and remove the hose. For winterizing I have a section of hose with a male fitting on one end and a large funnel on the other. I attach the hose to the fitting in the bilge, open the valve, and, standing in the cockpit pour a gallon of anti freeze into the funnel and watch it come out of the overboard discharge. This eliminates the need to turn on the A/C. Just make sure that you have dewatered the strainer and that the thru hull is closed for this operation or the anti freeze will go down to the thru hull.

Walter Naef
Mar y Sol
Hull #61

[wolfe10]

Another trick if you can get down to the A/C water DISCHARGE (i.e. in dingy or floating dock with that side toward the dock) is to put a hose up to the discharge port and run the shore water hose long enough (like 2-3 minutes) that you force the air from the system.

[JohnForr]

The A/C started pumping water again when I hit an unmarked reset button on top of a switch box mounted to the bulkhead next to the A/C unit.
Also, An A/C mechanic told me that if I just take the hose off the A/C side of the pump that it should start pumping. Since I found a popped reset button I did not have to disconnect hose.
My A/C is 13 years old. I don't know how much longer it can last. Rotary-Aire Model 50530 (17,000 BTU AC/reverse cycle heat) With digital control.

Happy New Year

[MarkElliott]

Went to the boat to get things going for the season. First wanted to get the heat going to dehumidify the boat from the spring rain. I left the outflow of the raw water pump unattached and cracked the seacock. Flowed water thru the pump passively (it is mounted at or below the waterline) until no more air came out, just a steady stream of water that I caught with a funnel to a cut off antifreeze jug. Reattached the line from pump outlet to AC/ heat pump unit. Power on, and, surprise! a steady stream of water out the thru hull. My only thought is that having the outflow attached to the heat pump unit gives it enough back pressure that dosent allow all the air to be purged from the pump. Might think about placing a 3 way valve or purge valve of some sort on the outflow to ease priming.