dometic head 1/2 full switch?

[Kwik]

I am trying to troubleshoot the Dometic Sealand Vacuflush maybe 500 model? It is on my 2004 240DA. The head panelboard on the sink shows 1/2 full. The tank is indeed very empty and cleaned out. I pulled the three float switches and checked them for physical operation. The full switch was stuck. Cleaned it up and I can hear it now actuating a relay on the vacuum pump. So, it is working. I put a meter on the other two. The lower switch seems to be functioning, (sometimes). I assume I should have continuity when the float is low. The middle switch does not seem to function at all. I cut the wires to the middle switch and landed them together on the plug side. I still show 1/2 full. I'm just about at wits end. I cannot find a reasonable troubleshooting guide for it. It is simply the "hey stupid, plug it in" troubleshooting guide. Anyone have experience?

Added. I unwired the switched leg and the 1/2 indicator went out. But, the vacuum pump did not start. I checked the fuse for the head in the helm. It is good.

 

[capecodcruiser]

Not familiar with that exact model, but on other vacuflush systems, the tank level has nothing to do with pump operation. 2 completely different systems. Are you sure you are correlating the 2 things together correctly??

 

[Kwik]

I have read about all I can find on it. So much so that I can't recall exactly what document said that the vacuum pump will be disabled when the tank is half full to keep from overfilling the tank. I think it may have been the owners manual for the boat itself. We have only had the boat two months and only know for sure of the vacuum pump running once for a flush.

But, the owners manual also said something about AC switch needs to be turned on. I have no switch for the head on my shore power panel. I have the fresh water pump and accessory switches turned on at the helm. The fresh water pump has not failed. It keeps pressure as it should.

 

[bajturner]

...said that the vacuum pump will be disabled when the tank is half full to keep from overfilling the tank.

This isn't how the vacuflush system has worked on any of my three Sea Rays. 1/2 indicator is just that...an indicator. The EMPTY indicator is the same, and should go out when the tank is no longer empty (essentially a 1/4 tank indicator).

The FULL (DO NOT FLUSH) indicator does disable the vacuum pump so you can't overfill the tank.

To me, a better use of the three sensors would be 1/4 (so you have some confirmation at pump-out that the tank likely is empty), 3/4 (instead of half), and FULL/disable.

This can be achieved with the same setup and shortening the 1/2 tube to be at a level that indicates 3/4 full. Just need some different labels on the panel...

 

[Kwik]

Ok. With the help I have gotten so far, I think I will move on from the floats. I will have to replace the 1/2 full fir sure because it isnt working. But, I will move to other components for the current issue.

I did a resistance test on the vacuum motor. It checks out good. I will look for a way to bypass the vacuum switch next. Going to have the boat tied up at the tire store this afternoon. But, hopefully they are done quickly enough for me to spend some time on it at home before dark.

 

[Kwik]

Ok. Feeling foolish. Manually pulled the spring on the vacuum switch. Tank was under vacuum. Pulled hose from the bottom of the commode. It sucked the hose dry. Couldnt get my hand down in the bowl. So, the wife double trash bagged her hand and found this. Any idea what the heck this is.