Just got back from our first overnight trip of the season.* All went well with the exception of the aft head.* We have 2 Vacuflush heads on board and*the aft head quit working last night.* I found the in-line fuse blown.* Replaced fuse and pump started, ran shortly (5-10 secs.) and blew again.* I removed the water from the bowl and there does not appear to be blockage between bowl and*vacuum tank.* I did not have time to take it further apart, but will be back down there later this week.* Any suggestions?* It seems that the likely culprit is something plugging the pump mechanism itself, causing the motor to struggle and the fuse blowing.* We have had virtually no issues with these heads in the 2 years we have owned the boat.*
Almost certainly a blockage, keep checking further down the line. It also might be a plugged vent line from the holding tank. That would cause a pressure buildup as well, but probably not the first thing to check for.