Vacu-Flush pump "freezes"

[Mirage35]

There's lots of discussion of Vacu-flush but I haven't seen this particular problem.

Occasionally after flushing the vacuum pump just doesn't run. I checked the power and vacuum switch and they're all okay. Then I discovered that if I just take a wrench and turn it a bit (at the joint where the motor drives the pump) it starts up again and works fine until the next time.

It doesn't appear to happen in the same position each time and I haven't thought of anything else it might correlate to. Our usage of the system hasn't changed (well, I'm a bit less constipated than I was but that's another story).

The duckbill valves are overdue for changing so I'm going to do that and take a look around while I'm at it, and would appreciate any suggestions of what to look for.

[Nicholson58]

Sounds totally mechanical. Look for dodgy bearings, alignment, stiff rubber bits etc

[peghall]

Sounds like an electrical/wiring problem. Here's how the VF troubleshooting guide describes the possible causes:

No power to the pump
Improper electrical connection
Faulty vacuum switch
Faulty motor

Because it's an occasional problem, I'm guessing there's a loose or broker wire. Otoh, it COULD be a failing vacuum switch. I know you said you checked it...but:there's a sensor in it that's supposed start the pump when the vacuum drops (flushing or an air leak), turn it off when sufficient vacuum has been achieved. Normally it just causes the pump run longer and longer after each flush until it finally stops shutting off the pump at all. but although it would be very unusual, it's possible that sensor is in the early stage of failing.



----Peggie

[Mirage35]

Electrical was the first thing I considered - had power at the right places, tried shorting across the vacuum switch terminals, nothing happened until I manually turned the pump.

In my experience intermittent connections don't fix themselves without at least wiggling some wires, so I'm having trouble thinking of what else to look at electrically.

[Nicholson58]

Can the motor be disassembled? Look for trouble with the brushes and commutator.

[peghall]

How old is your VF system?


--Peggie

[Mirage35]

Originally Posted by peghall

How old is your VF system?


--Peggie

Date code on the pump motor is 0910, so I'm guessing 11 years (it was installed by the PO). Was pretty lightly used until I bought the boat.

[peghall]

I'm not sure what you're putting a wrench on, 'cuz I dunno what there is to turn on a vacuum pump. If doing that gets the motor to run, the problem has to be in pump motor or connection to it. I have a schematic of the entire pump that I can attach to an email, although I'm not sure how much help it'll be.But if you want to send me a PM that includes your email address I'll send it to you. IMO, it's time to talk to a Dometic (formerly SeaLand) tech. Call Dometic in Ohio 800-321-9886 They'll give you the name and contact info for the nearest "authorized service center." They won't charge you anything to trouble shoot it on the phone.



--Peggie

[JC Reefer]

Originally Posted by Nicholson58

Can the motor be disassembled? Look for trouble with the brushes and commutator.

Sounds like you might have metal dust built up on one of the brushes. I’d pull the motor apart and clean it up. I removed one of these years ago and recall it being tough to do without having clear top access.

[Mirage35]

I'm probably having issues with the terminology but will keep trying.

The vacuum pump assembly has a drive motor and a bellows pump in an integrated unit. Under the plastic cover (see screen cap) they are connected together; that's where I'm turning the connection to move the moving parts. I'll add a photo tomorrow when I'm on the boat.

On reflection and re-reading the trouble-shooting guide, it's possible that it's a sticky vacuum switch, and just moving the parts is enough to un-stick it. It's also possible that something is stuck under the vacuum bellows. The difficulty with trouble-shooting an intermittent problem is ... you know.

Re the suggestions of motor problems and rebuilds: thanks for the ideas, but it looks like a sealed unit and I'm not going to open it up and try to fix it. If it gets to that point I have more spare money than spare time.

[Mirage35]

And, Peggie, thanks for the offer of the detailed schematic, but if it gets beyond the level of the wiring diagram in the manual it's farther than I want to go.

[peghall]

It is a sealed motor and one that's 11 years old...which is why I recommend that you talk to a factory tech about it. The motor can be replaced if necessary for a LOT less than the entire pump.


--Peggie

[Nicholson58]

Originally Posted by peghall

It is a sealed motor and one that's 11 years old...which is why I recommend that you talk to a factory tech about it. The motor can be replaced if necessary for a LOT less than the entire pump.


--Peggie

Very good advice!

- however - I consider most sealed anything just a mere challenge, a glove to the face. Many times with otherwise no options I have drilled out welds, rivets, etc. depends on your desperation. Might work until you can replace AND buy a spare.

[Mirage35]

For the moment I'm not going to replace anything that costs a few hundred dollars until I'm sure I'm replacing the right part. For now there's an adequate workaround until I figure out which part that is.

I'll continue my testing, probably call the manufacturer, and will update this thread for general information when I have a useful result.

[Mirage35]

For the information of those interested this is what the motor / pump connection looks like, and this is what I turn to kick-start the system.

No more new information. I'll update the thread if and when I get a positive indication of what is actually causing the problem. I replaced the duckbill valves since I was in there anyway, although they looked like they were in good condition, and didn't see anything else that looked out of the ordinary.