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Old 27-09-2019, 12:34   #1
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VacuFlush Overcycling

I have a vacuflush 506 with a vacuum generator model VG2-12. It wants to cycle continuously. I have replaced the seals and all 4 duckbills. It creates vaccum but doesn't want to shut off. I will shut off the switch manually after 60-70 cycles, come back in an hour or two and the green light will either be on or come on after a few more cycles, or if I jimmy the spring loaded plunger on the vacuum tank, the green light comes on. It does not appear to be leaking and maintains vacuum overnight with the green light on in the morning, water level in the bowl overnight maintained. I have tried to adjust the nut on the spring's plunger with no change. My assumption is the switch has failed. Is that a reasonable assumption.

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Old 27-09-2019, 12:58   #2
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Re: VacuFlush Overcycling

It sounds reasonable to me. If the switch carries any appreciable amount of current, the contacts may be worn and are starting to weld themselves together.

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Old 27-09-2019, 13:17   #3
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Re: VacuFlush Overcycling

Welcome to the forum.

The Vacuflush is a very easy system to maintain.

The Dometic Vacuflush 506 head could be a problem, if the seal was leaking, but the OP reports the bowl remains full, so that potential problem could be discounted.

The VG2-12 vacuum generator uses a piston bellows pump, w/ four duckbill (Joker) valves to create the vacuum.

The system vacuum is detected by the vacuum switch assembly where a diaphragm works against a spring and the position is detected by a switch.

The "easy" way to determine if the switch is good/bad is to unscrew it from the vacuum switch assembly and then manually actuate the plunger.

If that test shows the switch to be good, then the big suspicion I would have is the duckbill (Joker) valves. Those could invert, could be installed incorrectly oriented or the fittings could be over tightened, distorting the shape, keeping them open.

Whenever I plan on vacuum generator service w/ a functioning system, I first fill the bowl w/ water, then run a large slug of water through to the holding tank, until I can audibly hear the head drain hose to be empty. I shut off the water supply after the bowl is full, so the vacuum generator drains as much as possible.

My preference is to keep these parts scrubbed clean and properly inspected for issues to avoid / prevent problems.
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Old 27-09-2019, 13:19   #4
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Re: VacuFlush Overcycling

The vacuum tank switch has a little diaphragm in it that wears out. Sounds like that's what's happening here. Unfortunately you can't replace just that li'l diaphragm, you have to buy the whole vacuum switch. VacuFlush parts--except for duckbills--are only available from Dometic's regional authorized service centers...The main office is in Ohio...give 'em a call to get the number for nearest one to you: 800-321-9886

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Old 27-09-2019, 14:30   #5
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Re: VacuFlush Overcycling

Many thanks. The failed diaphragm fits with what I see happening and explains why jimmying the plunger slightly stops the cycling. I think I found the correct replacement on Amazon - Dometic 385310540 Vacuum Switch Kit
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