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AC Dometic Pump not running

K

Kirdud

Contributing Member
I have a Dometic AC (VCD10K/1-5MR) and a Dometic PML 250 115 VAC pump. This is the third pump that has been replaced within a year. I replaced the third one myself a month ago, and tonight, after 6 hours of operation, it stopped (HPF), and the water stopped flowing. What could be the issue with these pumps? Or is there a problem on my side? I will be grateful for any thoughts and ideas.
 
pretty sure they use the base March pump...mounted to their bracket with their label....

Overall, the March pumps are pretty reliable, at least thru their first decade of service...

Only thing I can think of is if there is a relay controlling it....if the relay's contacts are bad, that can induce a voltage drop and I dont think those pumps tolerate that for long...
 
The Murch pump and the Dometic look similar, and that's true. The issue is that I replaced the last pump a month ago, and it stopped working during the night. This weekend, I removed the hose from the seacock and primed the pump directly with fresh water from the dock. As soon as water started coming out of the outlet hose, I asked my wife to turn on the AC, and it started working well. I quickly removed the dock water hose and reconnected the seacock hose. The water continued to flow, and the AC kept running fine, but it started making noise.

I turned everything off, removed the AC pump, opened the wet part with the impeller, and checked it all, trying to find anything that might be stuck, but everything seemed fine. Then, I put it all back together and started it up, but unfortunately, the sound didn’t disappear, so I left it running overnight. In the morning, it had stopped again. I haven't had a chance to check it yet, but I believe it's the same issue - it lost priming for some reason.

For me, it’s strange because the pump seems to have a very simple construction. What else needs to be checked?
 
I conducted some additional tests. I forced the pump to run by priming it with dock water. However, it started with a sound, ran for 30 minutes to an hour, and then stopped. I replaced the current pump with the previous one, primed it, and it started again. It worked for 30-40 minutes before stopping. It stopped without showing the HPF message on the control panel. It just stopped pumping water, although the AC was still running, but I turned it off before the HPF message could appear. I tried to prime it again, but it wouldn’t start. It seems to be overheating for some reason. The strainer filter is clean, and the water flow after the strainer is perfect. What else could it be?

I opened the wet part, and it seems that the magnet is making that sound while rotating. Why this happened with the new pump after just 6 hours of operation is a question for me.
 
Sorry for the lag...i was 'off the grid' for a vacation....

If the pump if loosing prime, I'd make sure the installation was "per the book". Those pumps are NOT self priming and need to be mounted below the waterline. They should also have a fine strainer on the suction line. If those are ok, then I'd look for an air leak (eg a loose hose clamp, etc).

If the pump is still running but noisy and you have had 'loss of prime', then the ball bearing and or housing are probably damaged and need to be replaced....there are several shops that will sell parts via mail order but I haven't had the need to get any recently.
 
makomark said:
Sorry for the lag...i was 'off the grid' for a vacation....

If the pump if loosing prime, I'd make sure the installation was "per the book". Those pumps are NOT self priming and need to be mounted below the waterline. They should also have a fine strainer on the suction line. If those are ok, then I'd look for an air leak (eg a loose hose clamp, etc).

If the pump is still running but noisy and you have had 'loss of prime', then the ball bearing and or housing are probably damaged and need to be replaced....there are several shops that will sell parts via mail order but I haven't had the need to get any recently.
Click to expand...
Good day! The installation was done according to the manual, and everything looks fine. The pump is located near the waterline, the strainer (Perko) is in place and clean. When I disconnect the outflow hose from the strainer, water flows very well.

I suspect there might be an issue with the cleaning cap of the strainer and the rubber seal underneath it, but I need to check it this weekend. The rubber is in very bad condition, and sometimes, when I clean the filter and open and close the cap, it leaks. I try to adjust it to stop the leaking, but it might be allowing air to enter. I will check it.
 
with the inlet section being below the water line, the free flow from the disconnected hose really doesn't say much...

If the seal is deteriorated, I'd say its past due for replacement...

FWIW, a length of clear hose can be very useful in diagnosing water flow problems....
 
makomark said:
Kirdud: make any progress with your pump??
Click to expand...
Unfortunately, there has been no progress. The electricity reaches the pump when the AC starts, and the pump works. Yesterday, it was windy with big waves. I returned to the marina and tried to turn on the AC, but no water came out, though the pump made a sound. It seems the pump lost its prime.
 
if the pump is loosing its prime, then there is something leaking in the suction side or the pump is mounted too high.

if you remove the hose from the pump's inlet, does the water flow freely and continuously?
 
makomark said:
if the pump is loosing its prime, then there is something leaking in the suction side or the pump is mounted too high.

if you remove the hose from the pump's inlet, does the water flow freely and continuously?
Click to expand...
I will check it over the weekend. After the strainer, when I disconnect the hose to prime the water, it flows very well.
 
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