[sluggo]

it was time to swap out the old AC fresh water pump.  what the tech recommended was a pump that Dometic makes, but it comes with a generic label, but with the same ratings, GPM etc. it is brand new, instead of Red it is Blue. Anyway, he puts it in, and it wont pump, it turns on for a few seconds (so we know it is wired correctly) and it shuts itself off.  We check there is a good stream of freshwater coming thru the strainer to the pump.  And when we disconnect the pump from the water line, and blow thru the line, the water comes out as it should, so we know there is no restrictions in the line.  so what else?  Bad pump? (we actually put two different brand new blue pumps on, and neither worked).  is there a 'switch' somewhere that says if there isnt any water coming into the pump turn yourself off?  Other ideas?  TIA   Sluggo

[Misdirection]

Disconnect the line going to the AC unit and then try the pump to see if anything comes out. And try blowing air thru the AC unit.

One time on my old boat, I must have gotten some type of vapor lock in my AC unit. Pump would come on but no water came out. I ended up having to disconnect the input hoses and output hoses from the AC unit and let any residual water drain. My thought was I had water, air, then more water in the line and that was somehow locking it up.

Let us know how you make out.

Sent from my XT1635-01 using Tapatalk

[sluggo]

Disconnect the line going to the AC unit and then try the pump to see if anything comes out. And try blowing sir thru the AC unit.

One time on my old boat, I must have gotten some type of vapor lock in my AC unit.  Pump would come on but no water came out.  I ended up having to disconnect the input hoses and output hoses from the AC unit and let any residual water drain.  My thought was I had water, air, then more water in the line and that was somehow locking it up.

Let us know how you make out.

Sent from my XT1635-01 using Tapatalk

thanks for the quick response.  We have done all of that, and no we are not getting any water coming out of the pump to the AC unit.  We disconnected the water line to the AC on the other pump (that goes to the AC on the helm) and it shot water out of it.  
I will try to blow some air threw there and see.

[jclark003]

So if I'm reading this correctly your pump shuts off after only a few seconds? Have you check to see if you are getting continuous AC power to the pump?

Unless you have a very old system the air conditioning controller will energize the pump circuit during cooling and heating cycles, that is when the condenser and compressor are put into operation. So if your compressor is running the pump should be energized. If the condenser shuts down for any reason it will de-energize the pump.

Two or more AC units connected to one pump use a trigger relay so any one condenser can operate the pump. The trigger assembly is usually a separate small control box.

If you are comfortable working around 120VAC put a meter on the wires in the AC control box that lead out to the pump. If the wire leads to a smaller box then open that box up and meter the wires going to the pump (that is the trigger relay). If you do not show 120VAC while the compressor is on then you either have a bad trigger or a bad controller board. If you show AC power and the pump is not running then something is up with the pump (some have over-heat protection).

Another alternative is to wire the pump directly into your AC breaker panel and bypass the system controller entirely. If it runs and pumps water your pump is good and you need to look at the control circuitry.

Keep in mind that if the compressor is shutting down because of some other fault (high head pressure, etc) it will quickly shut down the system including the pump. If this happens however you should see an error code on the thermostat.

Sounds complicated but it really is pretty straight forward. Remember to exercise normal precautions working around 120 volts.

[sluggo]

So if I'm reading this correctly your pump shuts off after only a few seconds? Have you check to see if you are getting continuous AC power to the pump?

Unless you have a very old system the air conditioning controller will energize the pump circuit during cooling and heating cycles, that is when the condenser and compressor are put into operation. So if your compressor is running the pump should be energized. If the condenser shuts down for any reason it will de-energize the pump.

Two or more AC units connected to one pump use a trigger relay so any one condenser can operate the pump. The trigger assembly is usually a separate small control box.

If you are comfortable working around 120VAC put a meter on the wires in the AC control box that lead out to the pump. If the wire leads to a smaller box then open that box up and meter the wires going to the pump (that is the trigger relay). If you do not show 120VAC while the compressor is on then you either have a bad trigger or a bad controller board. If you show AC power and the pump is not running then something is up with the pump (some have over-heat protection).

Another alternative is to wire the pump directly into your AC breaker panel and bypass the system controller entirely. If it runs and pumps water your pump is good and you need to look at the control circuitry.

Keep in mind that if the compressor is shutting down because of some other fault (high head pressure, etc) it will quickly shut down the system including the pump. If this happens however you should see an error code on the thermostat.

Sounds complicated but it really is pretty straight forward. Remember to exercise normal precautions working around 120 volts.

thanks!  the old pump was working fine, except it was not pumping enough water thru, so we just removed it at the slice where it leads into the rest of the boat, so I don't think it is what you mention, but I will run it up the flag pole with my tech.
As we had 2 pumps, he did go back to the shop and hard wire one of them, and it acted the same way as it did on the boat, so I don't think it is the circuity.  But always good to check.  I'll let you know.  Thanks!

[Matta0413]

Are you priming the system? Sot sure where you seastrainer is but mine is hard plumbed right to the intake side of the pump. Take the cover off the seastrainer and slowly open the seacock until water over flows out of the top of the seastrainer. Then put the cap back on, and fully open the seastrainer. Did you say the Tech bench tested the pump and had the same symptom? Just a click and then nothing?

[Misdirection]

Matta has good advice here. Especially if your old pump was self priming and the new one is not.

Are you priming the system? Sot sure where you seastrainer is but mine is hard plumbed right to the intake side of the pump. Take the cover off the seastrainer and slowly open the seacock until water over flows out of the top of the seastrainer. Then put the cap back on, and fully open the seastrainer. Did you say the Tech bench tested the pump and had the same symptom? Just a click and then nothing?

Sent from my XT1635-01 using Tapatalk

[sluggo]

Are you priming the system?  Sot sure where you seastrainer is but mine is hard plumbed right to the intake side of the pump.  Take the cover off the seastrainer and slowly open the seacock until water over flows out of the top of the seastrainer.  Then put the cap back on, and fully open the seastrainer.  Did you say the Tech bench tested the pump and had the same symptom?  Just a click and then nothing?

Yes we primed the pump by doing what you said, and yes I said the tech bench tested the pump, and it ran for a few seconds and shut off, and it was primed as well (as far as I know).  His solution is to order new pumps, which is fine, but there is something in me that thinks we are missing something.  thanks for the help.

[Matta0413]

The fact that the old one was pumping fine just starting to wear out and now a new pump on the same wiring is not working is strange. Have you hooked the old one back up? Perhaps the old one wasn't pumping enough because it wasn't getting the amps it needed from the controller board. Are there any errors on the control panel? I chased a similar problem last year and it turn out to be a bad control panel. After I replaced the pump and the circuit board.

[sluggo]

The fact that the old one was pumping fine just starting to wear out and now a new pump on the same wiring is not working is strange.  Have you hooked the old one back up?  Perhaps the old one wasn't pumping enough because it wasn't getting the amps it needed from the controller board.  Are there any errors on the control panel?  I chased a similar problem last year and it turn out to be a bad control panel.  After I replaced the pump and the circuit board.

the only error I've gotten is HPF which occurred when the pump wasn't pumping any water, I assume it went into some sort of 'protection' mode as it should.
We believe the old one wasn't pumping enough water (water came out of the close thru hull just fine, it was the far thru hull that it just trickled) because the plastic impeller appears to be very worn, that it is you can see where it should be in the housing, but it is too worn to fit correctly.

As mentioned out solution is to go back to the name brand pump and forget the generic, should go on today or tomorrow, I'll let you know.

If we have any issues, I'll have the tech put a meter on to check the voltage etc.

Thanks for your help!! Sluggo