Dometic/Sealand Vacuum Generator issue

[Hardalee53]

Last month I hauled out my Tartan to do a bottom job. Once the boat was back in the water I started having an issue with my Dometic Vacuum Generator (VG12VDC)- or so I thought. The pump would run momentarily and them stop when you activated the switch at the head. The light at the switch would always stay red - never green indicating what I assumed to be insufficient vacuum. I first carefully loosened the hose at the pump coming from the toilet and saw that it was still under pressure - didn't expect that. So, I carefully relieved the pressure on that hose and proceeded to remove the entire pump clean it and I went ahead and replaced all four duckbills, which needed replacement, the bellows, two o-rings and vacuum switch and put everything back together, but I have the same issue. When I activate the switch the motor activates the bellows for about one revolution and then stops. Not sure what to do next other than replace the pump motor itself??

[peghall]

The problem is most likely either electrical or --believe it or not, a blocked holding tank vent.

Electrical: Check #10 in the trouble shooting guide for the reasons the "Pump will not run:"
I think you can rule out No power
Loose or broken electrical wiring
Improper electrical connection
Faulty vacuum switch
Improper wiring


Although yours isn't actually blowing the breaker, this article may help you figure out why the pump won't run:

The two most common reasons for a VacuFlush to trip the breaker are a blocked tank vent or a clogged vacuum pump--either the bellows or the duckbills, or both. The tank vent is easy to clear, scrape out the vent thru-hull with a screwdriver blade or whatever you have handy that works—which may require removing a screen but that’s ok ‘cuz screens actually create more problems than they solve. Then back flush the vent line with plenty of water. You can prevent future tank vent blockages by back flushing it every time you wash the boat and/or pump out.

Fixing the vacuum pump requires taking the pump apart to clean it out (and also replace the duckbill valves—4 of ‘em, two in, two out), so this is a problem that’s a lot easier and considerably more pleasant to prevent than it is to cure. If someone hasn't flushed something they shouldn't have, it's a certainty that you aren't putting enough water through it. Over time that will cause waste and toilet paper to build up in it till it finally jams up the bellows. And when the bellows can’t move, it causes the motor to overheat and trip the breaker.

If none of the above helps, it's time to talk to Dometic/SeaLand. The phone number for their main office in Ohio is 800-321-9886. They will refer you to their nearest regional "authorized service center." They'll be able to help you trouble-shoot it on the phone.

--Peggie

[Hardalee53]

Thanks Peggy. I am checking the vent issue first and then I will check electrical (continuity of the pump motor) and check connections at breaker.

[SVHarmonie]

One more question on the same theme that Peggy started... check the alignment of your valves... a closed seacock and/or threeway valve will do this too...

For some reason the pump can't push OUT what it is try to push. Check the simple stuff first. I am not a huge believer in coincidences, although they DO happen... Moving a valve during the haulout could be the issue...